Home » Public Forums » GMCnet » Air cleaner design question (A question for you engineer types)
| Air cleaner design question [message #232539] |
Sat, 07 December 2013 08:24  |
kerry pinkerton
Messages: 2565
Registered: July 2012
Location: Harvest, Al
Karma: 15
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I've been around big blocks engines most my adult life. Most of them had the stock air snorkel concept on the air cleaner. A few 'high performance' machines had dual snorkle. On our 440 MOPARS, we would turn the air cleaner top upside down to create a gap and allow more air through the carb.
To my feeble mind, the diameter of the snorkle being considerably less than the bores of the carb is roughly equivalent to trying to breathe through a straw.
I know the GM designers were bright guys but can someone explain how a restrictive air input helps the engine? This is further complicated by long air ducts with many curves and bends that a lot of us put on our coaches.
I understand a bit about the velocity increasing when the throat narrows and can see where getting the air moving faster could be an advantage in a high RPM condition but we don't have high RPM conditions.
This week, I went with a friend to pick up his 'new' SOB. It has a 454 Chevy in it and has a factory duct from the snorkle out to clean air in front of the radiator just like we do. THE DIFFERENCE however is that the snorkle, instead of having a 2-3" diameter end has about a 6"x2" oval opening. The 4" inlet duct goes to a round to oval transition and mates up to the much larger oval snorkle on the 454 air cleaner.
This seems like a much, MUCH better arrangement. One of my things on my to do list for some time is to shape a new, larger snorkle and figure a way to get a strighter air inlet duct. I'd like to talk to Barry Owen (ex NASCAR GMCer) about where the high pressure points are on our coaches. I don't THINK that down low near the bottom of the drivers side of the radiator is the best place for heat or air flow but that is just an opinion.
Thoughts?
Kerry Pinkerton - North Alabama
Had 5 over the years. Currently have a '06 Fleetwood Discovery 39L
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| Re: [GMCnet] Air cleaner design question [message #232541 is a reply to message #232539] |
Sat, 07 December 2013 08:59  |
Mr ERFisher
Messages: 7117
Registered: August 2005
Karma: 2
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Sure wish you would list your products on a web site
FREE WIFI @ Mickey D
On Dec 7, 2013, at 6:24 AM, Kerry Pinkerton <Pinkertonk@MCHSI.com> wrote:
>
>
> I've been around big blocks engines most my adult life. Most of them had the stock air snorkel concept on the air cleaner. A few 'high performance' machines had dual snorkle. On our 440 MOPARS, we would turn the air cleaner top upside down to create a gap and allow more air through the carb.
>
> To my feeble mind, the diameter of the snorkle being considerably less than the bores of the carb is roughly equivalent to trying to breathe through a straw.
>
> I know the GM designers were bright guys but can someone explain how a restrictive air input helps the engine? This is further complicated by long air ducts with many curves and bends that a lot of us put on our coaches.
>
> I understand a bit about the velocity increasing when the throat narrows and can see where getting the air moving faster could be an advantage in a high RPM condition but we don't have high RPM conditions.
>
> This week, I went with a friend to pick up his 'new' SOB. It has a 454 Chevy in it and has a factory duct from the snorkle out to clean air in front of the radiator just like we do. THE DIFFERENCE however is that the snorkle, instead of having a 2-3" diameter end has about a 6"x2" oval opening. The 4" inlet duct goes to a round to oval transition and mates up to the much larger oval snorkle on the 454 air cleaner.
>
> This seems like a much, MUCH better arrangement. One of my things on my to do list for some time is to shape a new, larger snorkle and figure a way to get a strighter air inlet duct. I'd like to talk to Barry Owen (ex NASCAR GMCer) about where the high pressure points are on our coaches. I don't THINK that down low near the bottom of the drivers side of the radiator is the best place for heat or air flow but that is just an opinion.
>
> Thoughts?
> --
> Kerry Pinkerton
>
> North Alabama, near Huntsville,
>
> 77 Eleganza II, "The Lady", 403CI, also a 76 Eleganza being re-bodied as an Art Deco car hauler
> _______________________________________________
> GMCnet mailing list
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| Re: [GMCnet] Air cleaner design question [message #232542 is a reply to message #232541] |
Sat, 07 December 2013 09:08 |
Kingsley Coach
Messages: 2691
Registered: March 2009
Location: Nova Scotia Canada
Karma: -34
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I THINK..and that's a dangerous word for me...but didn't I see where a
couple of guys relocated the front signal/park light assembly and cut out
that area to duct in fresh air??
Mike in NS
On Sat, Dec 7, 2013 at 10:59 AM, <mr.erfisher@gmail.com> wrote:
> Sure wish you would list your products on a web site
>
> FREE WIFI @ Mickey D
>
>
>
>
>
> On Dec 7, 2013, at 6:24 AM, Kerry Pinkerton <Pinkertonk@MCHSI.com> wrote:
>
> >
> >
> > I've been around big blocks engines most my adult life. Most of them
> had the stock air snorkel concept on the air cleaner. A few 'high
> performance' machines had dual snorkle. On our 440 MOPARS, we would turn
> the air cleaner top upside down to create a gap and allow more air through
> the carb.
> >
> > To my feeble mind, the diameter of the snorkle being considerably less
> than the bores of the carb is roughly equivalent to trying to breathe
> through a straw.
> >
> > I know the GM designers were bright guys but can someone explain how a
> restrictive air input helps the engine? This is further complicated by
> long air ducts with many curves and bends that a lot of us put on our
> coaches.
> >
> > I understand a bit about the velocity increasing when the throat narrows
> and can see where getting the air moving faster could be an advantage in a
> high RPM condition but we don't have high RPM conditions.
> >
> > This week, I went with a friend to pick up his 'new' SOB. It has a 454
> Chevy in it and has a factory duct from the snorkle out to clean air in
> front of the radiator just like we do. THE DIFFERENCE however is that the
> snorkle, instead of having a 2-3" diameter end has about a 6"x2" oval
> opening. The 4" inlet duct goes to a round to oval transition and mates up
> to the much larger oval snorkle on the 454 air cleaner.
> >
> > This seems like a much, MUCH better arrangement. One of my things on my
> to do list for some time is to shape a new, larger snorkle and figure a way
> to get a strighter air inlet duct. I'd like to talk to Barry Owen (ex
> NASCAR GMCer) about where the high pressure points are on our coaches. I
> don't THINK that down low near the bottom of the drivers side of the
> radiator is the best place for heat or air flow but that is just an opinion.
> >
> > Thoughts?
> > --
> > Kerry Pinkerton
> >
> > North Alabama, near Huntsville,
> >
> > 77 Eleganza II, "The Lady", 403CI, also a 76 Eleganza being re-bodied as
> an Art Deco car hauler
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> > http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
--
Michael Beaton
1977 Kingsley 26-11
1977 Eleganza II 26-3
Antigonish, NS
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| Re: Air cleaner design question [message #232559 is a reply to message #232539] |
Sat, 07 December 2013 12:36 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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| Kerry Pinkerton wrote on Sat, 07 December 2013 09:24 |
I've been around big blocks engines most my adult life. Most of them had the stock air snorkel concept on the air cleaner. A few 'high performance' machines had dual snorkle. On our 440 MOPARS, we would turn the air cleaner top upside down to create a gap and allow more air through the carb.
To my feeble mind, the diameter of the snorkle being considerably less than the bores of the carb is roughly equivalent to trying to breathe through a straw.
I know the GM designers were bright guys but can someone explain how a restrictive air input helps the engine? This is further complicated by long air ducts with many curves and bends that a lot of us put on our coaches.
I understand a bit about the velocity increasing when the throat narrows and can see where getting the air moving faster could be an advantage in a high RPM condition but we don't have high RPM conditions.
This week, I went with a friend to pick up his 'new' SOB. It has a 454 Chevy in it and has a factory duct from the snorkle out to clean air in front of the radiator just like we do. THE DIFFERENCE however is that the snorkle, instead of having a 2-3" diameter end has about a 6"x2" oval opening. The 4" inlet duct goes to a round to oval transition and mates up to the much larger oval snorkle on the 454 air cleaner.
This seems like a much, MUCH better arrangement. One of my things on my to do list for some time is to shape a new, larger snorkle and figure a way to get a strighter air inlet duct. I'd like to talk to Barry Owen (ex NASCAR GMCer) about where the high pressure points are on our coaches. I don't THINK that down low near the bottom of the drivers side of the radiator is the best place for heat or air flow but that is just an opinion.
Thoughts?
|
Kerry,
As usual, your thoughts are well arranged and well placed.
The air inlet snout will probably only be an issue when the engine is at WOT and over 4500 RPM. There are other limiters in the system too. The intake has got to be a flow disaster, but it is what fit. Why do you think that a 403 is a effective power plant at less than 90% of the displacement of a 455?
The air intake snout is the way it is largely because of emissions. It has to be that way for the manifold heated air stove to do any good at all. If you are going to TBI, it is a non-issue. If you are not going to drive slowly on wet spring days, but the air stove and the manifold heater are unnecessary.
There were emissions restrictions even that early. When Muskie was running, he shoved through some regulations that we are still suffering with today.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: Air cleaner design question [message #232572 is a reply to message #232539] |
Sat, 07 December 2013 16:50 |
cbryan
Messages: 451
Registered: May 2012
Location: Ennis, Texas
Karma: 3
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Kerry,
Well, the situation is a conundrum for me. My 500 Cadillac setup has a very small wrist in the snorkel, coupled to a big hose and the transition from intake hose to snorkel is abrupt, too.
Other lore has it that ram air induction by putting the intake out in the air stream will give a boost in horsepower. (It will compress the air going into the engine intake, closer molecules mean more power.) To quote Phil Irving, who wrote in "Motorcycle Engineering", a classic, Page 272. "facing the intake forward is a thing to be avoided" (mostly because of carburetion issues), and if faced forward, "the theoretical increase of power due to increased pressure is 1.2 per cent at 100 mph, 2.7 per cent at 150 mph, and 4.8 per cent at 200 mph". He goes on to say that these increases are of little moment except for world speed record attempts.
For the GMC motorhome, that air taken from behind the turn signal escutcheon might be cooler and more dense with higher pressure than air from inside the radiator "plenum". Note that the stock intake in the GMC does not face forward, and takes its air from behind a dome affair. Diesel engines, which "like" better breathing and bigger exhaust, "like" to take their intakes high up off the road because presumably the air is cooler and more dense there. Diesels have no appreciable intake vacuum, have to have pumps to get vacuum, don't really understand this, but I think it's true.
I have experienced carburetor icing in Wyoming in a 1975 Dodge 318 15-passenger van with the exhaust manifold carburetor heat system butterfly rusted open. Weather conditions were: 11 degrees Fahrenheit, blowing snow (snow do blow in Wyoming), altitude about 4000 feet. Engine completely warm and working fairly hard. 2 barrel B&B carb. We sat beside the side of the road after complete shut down, tried starting again, it ran perfectly (ice melted from residual engine heat), until it iced up again.
The exhaust butterfly (when working properly) is closed on one manifold header pipe when cold, using a spiral bimetallic coil, causing the exhaust to be sent through the intake manifold crossover to the other side and out to the muffler, heating the base of the carb in the bargain. There was no carb icing in 15 years of running in Colorado in all conditions otherwise, rusted open always. That includes ski trips to altitude. That engine compartment is quite cramped and hot under normal circumstances. I became a fan of the newer method of using vacuum-operated exhaust manifold heat stove-derived carburetor heat using the flapper in the snorkel subsequently. It is supposed to keep the intake air at 83 degrees through a thermostat in the air cleaner modulating vacuum to the vacuum actuator in the snorkel, though, so some benefits from cooler air were negated by the apparent need to closely control the intake temperature.
Further observations of a 1994 Ford 15-passenger van with the 351 V8 multiport fuel injection shows a snorkel with the intake just behind the grille, but shielded from direct air blast. But, there are two side by side venturi-looking affairs it goes into that look like those cone shaped bodies in a Dyson vacuum cleaner. The restriction looks to be extreme and the resulting intake honk or moan is fairly loud. Are they trying for some consistent vacuum under part throttle in the intake system due to the restriction, and then live with the restriction under full throttle conditions? I might add that the exhaust pipe of that vehicle shows the same rust outside and inside, no carbon whatsoever, after 84,000 miles and for a 15 passenger van, the gas mileage is really good for that era. I think the throttle body really causes most of the intake vacuum under most conditions in a gasoline fueled engine, so there's quite a restriction there, so much so that under most situations intake restriction of a mild sort may not be too important.
Lastly, looking at hot rodders who are using carbs, some are finding 10% horsepower increases by adding 1" spacers just under the air cleaner or plenum body. Some applications, I hasten to add. That's of interest because of our limited space to raise our air cleaners or plenums. Benefit is derived from a more direct path for the air, I guess. Some intake tuning effect, maybe.
This might be a systems engineering situation in that changing one parameter might cause trouble in another. The new oval intake you describe may be because the computers in more modern engines are faster and can adjust mixture quickly enough for situations like following behind another vehicle, with the draft causing rapid changes in atmospheric pressure. That's another stretch, though. Just don't know.
I hope it can be solved for the GMC. No reason for not trying, as stewards of a very long-lived product, and we needn't wait until the next model to have it solve the problem. There won't be a next model. Here's to 11 mpg.
Carey Bryan
Carey from Ennis, Texas
78 Royale, 500 Cadillac, Rance Baxter EFI.
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| Re: Air cleaner design question [message #232575 is a reply to message #232572] |
Sat, 07 December 2013 16:59 |
tphipps
Messages: 3005
Registered: August 2004
Location: Spanish Fort, AL
Karma: 9
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Senior Member |
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I have always thought that a straighter air path would be a good thing. Cooler outside air would be denser than the heated engine compartment. But, reading the other comments, drivability may suffer in different climates, than our warm South.
While we are thinking about this, how about a NACA type air intake located along the driver side of the vehicle, directly with only one turn to the air cleaner? Would this work?
Tom, MS II
2012 Phoenix Cruiser model 2552
KA4CSG
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| Re: [GMCnet] Air cleaner design question [message #232586 is a reply to message #232575] |
Sat, 07 December 2013 17:52 |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Senior Member |
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Tom,
This is interesting, I found two 3" wide NACA scoops on eBay awhile back and bought two of them. When they arrived I held them up
against the front "corner" of the GMC and it fit the contour PERFECTLY; I figger on installing one on each side. I also found a
Toronado air cleaner with two snorkels. I'll cut off the snorkel so that the OD just fits the ID of some 3" flexible ducting to feed
them from the NACA scoops.
Regards,
Rob M.
Sydney, Australia
AUS '75 Avion-The Blue Streak TZE365V100428
USA '75 Avion-Double Trouble TZE365V100426
-----Original Message-----
From: Thomas Phipps
I have always thought that a straighter air path would be a good thing. Cooler outside air would be denser than the heated engine
compartment. But, reading the other comments, drivability may suffer in different climates, than our warm South.
While we are thinking about this, how about a NACA type air intake located along the driver side of the vehicle, directly with only
one turn to the air cleaner? Would this work?
Tom, MS II
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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| Re: [GMCnet] Air cleaner design question [message #232590 is a reply to message #232572] |
Sat, 07 December 2013 18:05 |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Carey,
I have a Ragusa aluminum air scoop installed in the top driver side of the grill on Double Trouble. It feeds the OEM air cleaner
through a 4" dryer hose.
http://www.gmcmhphotos.com/photos/random-photos/p52056-ragusa-air-scoop.html
It works fine probably because I've never gotten to 100mph! ;-)
Regards,
Rob M.
Sydney, Australia
AUS '75 Avion-The Blue Streak TZE365V100428
USA '75 Avion-Double Trouble TZE365V100426
-----Original Message-----
From: Carey Bryan
Kerry,
Well, the situation is a conundrum for me. My 500 Cadillac setup has a very small wrist in the snorkel, coupled to a big hose and
the transition from intake hose to snorkel is abrupt, too.
Other lore has it that ram air induction by putting the intake out in the air stream will give a boost in horsepower. (It will
compress the air going into the engine intake, closer molecules mean more power.) To quote Phil Irving, who wrote in "Motorcycle
Engineering", a classic, Page 272. "facing the intake forward is a thing to be avoided" (mostly because of carburetion issues), and
if faced forward, "the theoretical increase of power due to increased pressure is 1.2 per cent at 100 mph, 2.7 per cent at 150 mph,
and 4.8 per cent at 200 mph". He goes on to say that these increases are of little moment except for world speed record attempts.
For the GMC motorhome, that air taken from behind the turn signal escutcheon might be cooler and more dense with higher pressure
than air from inside the radiator "plenum". Note that the stock intake in the GMC does not face forward, and takes its air from
behind a dome affair. Diesel engines, which "like" better breathing and bigger exhaust, "like" to take their intakes high up off
the road because presumably the air is cooler and more dense there. Diesels have no appreciable intake vacuum, have to have pumps
to get vacuum, don't really understand this, but I think it's true.
I have experienced carburetor icing in Wyoming in a 1975 Dodge 318 15-passenger van with the exhaust manifold carburetor heat system
butterfly rusted open. Weather conditions were: 11 degrees Fahrenheit, blowing snow (snow do blow in Wyoming), altitude about 4000
feet. Engine completely warm and working fairly hard. 2 barrel B&B carb. We sat beside the side of the road after complete shut
down, tried starting again, it ran perfectly (ice melted from residual engine heat), until it iced up again.
The exhaust butterfly (when working properly) is closed on one manifold header pipe when cold, using a spiral bimetallic coil,
causing the exhaust to be sent through the intake manifold crossover to the other side and out to the muffler, heating the base of
the carb in the bargain. There was no carb icing in 15 years of running in Colorado in all conditions otherwise, rusted open
always. That includes ski trips to altitude. That engine compartment is quite cramped and hot under normal circumstances. I
became a fan of the newer method of using vacuum-operated exhaust manifold heat stove-derived carburetor heat using the flapper in
the snorkel subsequently. It is supposed to keep the intake air at 83 degrees through a thermostat in the air cleaner modulating
vacuum to the vacuum actuator in the snorkel, though, so some benefits from cooler air were negated by the apparent need to closely
control the intake temperature.
Further observations of a 1994 Ford 15-passenger van with the 351 V8 multiport fuel injection shows a snorkel with the intake just
behind the grille, but shielded from direct air blast. But, there are two side by side venturi-looking affairs it goes into that
look like those cone shaped bodies in a Dyson vacuum cleaner. The restriction looks to be extreme and the resulting intake honk or
moan is fairly loud. Are they trying for some consistent vacuum under part throttle in the intake system due to the restriction,
and then live with the restriction under full throttle conditions? I might add that the exhaust pipe of that vehicle shows the same
rust outside and inside, no carbon whatsoever, after 84,000 miles and for a 15 passenger van, the gas mileage is really good for
that era. I think the throttle body really causes most of the intake vacuum under most conditions in a gasoline fueled engine, so
there's quite a restriction there, so much so that under most situations in take restriction of a mild sort may not be too
important.
Lastly, looking at hot rodders who are using carbs, some are finding 10% horsepower increases by adding 1" spacers just under the
air cleaner or plenum body. Some applications, I hasten to add. That's of interest because of our limited space to raise our air
cleaners or plenums. Benefit is derived from a more direct path for the air, I guess. Some intake tuning effect, maybe.
This might be a systems engineering situation in that changing one parameter might cause trouble in another. The new oval intake
you describe may be because the computers in more modern engines are faster and can adjust mixture quickly enough for situations
like following behind another vehicle, with the draft causing rapid changes in atmospheric pressure. That's another stretch,
though. Just don't know.
I hope it can be solved for the GMC. No reason for not trying, as stewards of a very long-lived product, and we needn't wait until
the next model to have it solve the problem. There won't be a next model. Here's to 11 mpg.
Carey
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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| Re: [GMCnet] Air cleaner design question [message #232607 is a reply to message #232539] |
Sat, 07 December 2013 19:48 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Senior Member |
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Thought:
I ogt a MagneHelix guage kicking around... Sometime when I'm bored it wuld be worth using ti to compare underhood absolute pressure to inside the air cleaner canister and inside the filter element itself at various throttle settings. I always thought that was why Mopar put the raised ridge on the 'pie pan'.
--johnny
'76 23' transmode norriss
________________________________
From: Kerry Pinkerton <Pinkertonk@MCHSI.com>
To: gmclist@temp.gmcnet.org
Sent: Saturday, December 7, 2013 9:24 AM
Subject: [GMCnet] Air cleaner design question
I've been around big blocks engines most my adult life. Most of them had the stock air snorkel concept on the air cleaner. A few 'high performance' machines had dual snorkle. On our 440 MOPARS, we would turn the air cleaner top upside down to create a gap and allow more air through the carb.
To my feeble mind, the diameter of the snorkle being considerably less than the bores of the carb is roughly equivalent to trying to breathe through a straw.
I know the GM designers were bright guys but can someone explain how a restrictive air input helps the engine? This is further complicated by long air ducts with many curves and bends that a lot of us put on our coaches.
I understand a bit about the velocity increasing when the throat narrows and can see where getting the air moving faster could be an advantage in a high RPM condition but we don't have high RPM conditions.
This week, I went with a friend to pick up his 'new' SOB. It has a 454 Chevy in it and has a factory duct from the snorkle out to clean air in front of the radiator just like we do. THE DIFFERENCE however is that the snorkle, instead of having a 2-3" diameter end has about a 6"x2" oval opening. The 4" inlet duct goes to a round to oval transition and mates up to the much larger oval snorkle on the 454 air cleaner.
This seems like a much, MUCH better arrangement. One of my things on my to do list for some time is to shape a new, larger snorkle and figure a way to get a strighter air inlet duct. I'd like to talk to Barry Owen (ex NASCAR GMCer) about where the high pressure points are on our coaches. I don't THINK that down low near the bottom of the drivers side of the radiator is the best place for heat or air flow but that is just an opinion.
Thoughts?
--
Kerry Pinkerton
North Alabama, near Huntsville,
77 Eleganza II, "The Lady", 403CI, also a 76 Eleganza being re-bodied as an Art Deco car hauler
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Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: [GMCnet] Air cleaner design question [message #232625 is a reply to message #232607] |
Sun, 08 December 2013 00:46 |
Bullitthead
Messages: 1411
Registered: November 2013
Karma: 5
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Senior Member |
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Kerry,
We have the perfect vehicle for experimenting with the engine while driving. Get the engine up to normal temp and make a run or two down a vacant road. Then pop the hatch real quick and take the air cleaner off. You can put a screen over the carb to safeguard the intake from debris. Then make the same runs down the road. If you can feel a difference in power, then you know that you can make a change. I have learned that the Q-jet needs space on top of it or the airflow will be disrupted and cause part and full throttle driveability issues. I put a snorkel assembly from a Grand Cherokee 360 V8 on a Q-jet and it even caused idle fluctuations, it was too close to the top of the carb. And it's only feeding the 2.8 V6 in my Bronco. But it had a nice big hose leading to it and it worked well on the Jeep 360, so what was the deal? It was the fuel injection on the jeep that made it work on there. So even though it looked like a perfect setup, it didn't work on a carb.
Also, engines do not suck air in, the atmosphere pushes the air into the engine. It's just a difference in pressure that makes the air flow. That's why Ram Air on the Pontiacs worked, but it's just a tiny increase in pressure outside of the engine and so was just a tiny increase in power. At least until you crest 100 mph. Anything you can do to make that path easier will increase performance, but you may not be able to notice except when you've really got your foot in it.
There is more power to be gained by having cool intake air. That's why draggers will hook up an ice chest in the intake plumbing to get that extra 8 horsepower.
Terry Kelpien
ASE Master Technician
73 Glacier 260
Smithfield, Va.
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| Re: [GMCnet] Air cleaner design question [message #232635 is a reply to message #232539] |
Sun, 08 December 2013 06:11 |
Steven Ferguson
Messages: 3447
Registered: May 2006
Karma: 0
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Senior Member |
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I used a Jeep air duct pulling air through a 3" x 6' long ribbed hose that
terminated with a typical conical shaped K& N air filter. With a 1" spacer
between the air duct and the carb, the chassis dyno testing showed the
exact same torque and horsepower numbers on the rpm curve with the setup as
with nothing on top of the carb. The pulls were off idle to 4,400 rpm. I
think it would be wise to look elsewhere for gains.
Steve F.
On Sat, Dec 7, 2013 at 7:24 AM, Kerry Pinkerton <Pinkertonk@mchsi.com>wrote:
>
>
> I've been around big blocks engines most my adult life. Most of them had
> the stock air snorkel concept on the air cleaner. A few 'high performance'
> machines had dual snorkle. On our 440 MOPARS, we would turn the air
> cleaner top upside down to create a gap and allow more air through the carb.
>
> To my feeble mind, the diameter of the snorkle being considerably less
> than the bores of the carb is roughly equivalent to trying to breathe
> through a straw.
>
> I know the GM designers were bright guys but can someone explain how a
> restrictive air input helps the engine? This is further complicated by
> long air ducts with many curves and bends that a lot of us put on our
> coaches.
>
> I understand a bit about the velocity increasing when the throat narrows
> and can see where getting the air moving faster could be an advantage in a
> high RPM condition but we don't have high RPM conditions.
>
> This week, I went with a friend to pick up his 'new' SOB. It has a 454
> Chevy in it and has a factory duct from the snorkle out to clean air in
> front of the radiator just like we do. THE DIFFERENCE however is that the
> snorkle, instead of having a 2-3" diameter end has about a 6"x2" oval
> opening. The 4" inlet duct goes to a round to oval transition and mates up
> to the much larger oval snorkle on the 454 air cleaner.
>
> This seems like a much, MUCH better arrangement. One of my things on my
> to do list for some time is to shape a new, larger snorkle and figure a way
> to get a strighter air inlet duct. I'd like to talk to Barry Owen (ex
> NASCAR GMCer) about where the high pressure points are on our coaches. I
> don't THINK that down low near the bottom of the drivers side of the
> radiator is the best place for heat or air flow but that is just an opinion.
>
> Thoughts?
> --
> Kerry Pinkerton
>
> North Alabama, near Huntsville,
>
> 77 Eleganza II, "The Lady", 403CI, also a 76 Eleganza being re-bodied as
> an Art Deco car hauler
> _______________________________________________
> GMCnet mailing list
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>
--
Take care,
Steve
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| Re: Air cleaner design question [message #232639 is a reply to message #232539] |
Sun, 08 December 2013 11:26 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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They probably used it as it was an off the shelf Olds piece, it fit under the hatch, the reverse megaphone silencer met noise spec and it was ready to go for the Thermac. I have a salvage one from a swap meet marked Cutlass. Since I haven't found a dual that is HEI ready, plan is to fab a second Pontiac large oval type to the passenger side of the salvage unit and feed that side vac motor manifold vac as GM did on the dual snorkel muscle cars. That way the preheat still works. That dimple in the lid at the wingnut is extremely important. When you flip the lid you defeat that air smoothing function.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: Air cleaner design question [message #232641 is a reply to message #232539] |
Sun, 08 December 2013 13:51 |
habbyguy
Messages: 896
Registered: May 2012
Location: Mesa, AZ
Karma: 3
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Senior Member |
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It can look like the nose of the air cleaner inlet tube is a limiting factor, but the square inches of that clean, unobstructed opening is going to be a lot bigger than that of the combined carburetor barrels (which are far from clean and unobstructed). Also, I would tend to think that any air filter is going to have more restriction to air flow than the air cleaner housing opening.
On my rig, I've rigged a length of 4" dryer hose from a fiberglass ram air scoop (thanks, Jim K) to my stock air cleaner. I had to smoosh the dryer hose in a couple places to get clearance, but I'm betting I'm flowing more - and certainly cooler - air than I would be if the engine was breathing through only the original air cleaner. I connected the hose to the nose of the filter housing by just clamping it around.
When I install my TBI fuel injection system, I'm going with a Jeep Grand Cherokee air filter (with snorkel and offset "decent size" air filter), hooked to the scoop. That should provide the best of all words, and I'm hopeful that my mighty 403 will be putting out more power than ever, and that it will be much happier at very high altitude (though mainly due to TBI, not any improvements in air cleaner or ducting).
Mark Hickey
Mesa, AZ
1978 Royale Center Kitchen
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| Re: [GMCnet] Air cleaner design question [message #232645 is a reply to message #232641] |
Sun, 08 December 2013 15:06 |
emerystora
Messages: 4442
Registered: January 2004
Karma: 13
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Senior Member |
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I don't see how you would get a bigger air flow using a 4 inch duct if you clamp it to the end of the stock air cleaner. The opening in the air cleaner nozzle is a lot smaller than 4" diameter so that restriction would moke the air flow the same.
Emery Stora
On Dec 8, 2013, at 12:51 PM, Mark <mark@habcycles.com> wrote:
>
>
> It can look like the nose of the air cleaner inlet tube is a limiting factor, but the square inches of that clean, unobstructed opening is going to be a lot bigger than that of the combined carburetor barrels (which are far from clean and unobstructed). Also, I would tend to think that any air filter is going to have more restriction to air flow than the air cleaner housing opening.
>
> On my rig, I've rigged a length of 4" dryer hose from a fiberglass ram air scoop (thanks, Jim K) to my stock air cleaner. I had to smoosh the dryer hose in a couple places to get clearance, but I'm betting I'm flowing more - and certainly cooler - air than I would be if the engine was breathing through only the original air cleaner. I connected the hose to the nose of the filter housing by just clamping it around.
>
> When I install my TBI fuel injection system, I'm going with a Jeep Grand Cherokee air filter (with snorkel and offset "decent size" air filter), hooked to the scoop. That should provide the best of all words, and I'm hopeful that my mighty 403 will be putting out more power than ever, and that it will be much happier at very high altitude (though mainly due to TBI, not any improvements in air cleaner or ducting).
> --
> Mark Hickey
> Mesa, AZ
> 1978 Royale Center Kitchen
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
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| Re: [GMCnet] Air cleaner design question [message #232647 is a reply to message #232645] |
Sun, 08 December 2013 15:34 |
Gary Worobec
Messages: 867
Registered: May 2005
Karma: -1
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Senior Member |
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I concur with Steve F. When I did my EFI I used a Jeep adapter plus a 1 1/2
Holley spacer and 4" aluminum tubing to the front of coach and a K-N type
air clear with a foam pre filter. No change in response/mileage/noise.
Narrowing down the intake at the carb or throttle body speeds up the air
flow allowing for better "swirling" and fuel atomization. Slow air into the
carb or throttle body results in a rich mixture and bad mileage.
Thanks,
Gary and Joanne Worobec
1973 GMC Glacier
Anza, CA
-----Original Message-----
From: gmclist-bounces@temp.gmcnet.org
[mailto:gmclist-bounces@temp.gmcnet.org] On Behalf Of Emery Stora
Sent: Sunday, December 08, 2013 1:07 PM
To: gmclist@temp.gmcnet.org
Subject: Re: [GMCnet] Air cleaner design question
I don't see how you would get a bigger air flow using a 4 inch duct if you
clamp it to the end of the stock air cleaner. The opening in the air
cleaner nozzle is a lot smaller than 4" diameter so that restriction would
moke the air flow the same.
Emery Stora
On Dec 8, 2013, at 12:51 PM, Mark <mark@habcycles.com> wrote:
>
>
> It can look like the nose of the air cleaner inlet tube is a limiting
factor, but the square inches of that clean, unobstructed opening is going
to be a lot bigger than that of the combined carburetor barrels (which are
far from clean and unobstructed). Also, I would tend to think that any air
filter is going to have more restriction to air flow than the air cleaner
housing opening.
>
> On my rig, I've rigged a length of 4" dryer hose from a fiberglass ram air
scoop (thanks, Jim K) to my stock air cleaner. I had to smoosh the dryer
hose in a couple places to get clearance, but I'm betting I'm flowing more -
and certainly cooler - air than I would be if the engine was breathing
through only the original air cleaner. I connected the hose to the nose of
the filter housing by just clamping it around.
>
> When I install my TBI fuel injection system, I'm going with a Jeep Grand
Cherokee air filter (with snorkel and offset "decent size" air filter),
hooked to the scoop. That should provide the best of all words, and I'm
hopeful that my mighty 403 will be putting out more power than ever, and
that it will be much happier at very high altitude (though mainly due to
TBI, not any improvements in air cleaner or ducting).
> --
> Mark Hickey
> Mesa, AZ
> 1978 Royale Center Kitchen
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
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| Re: Air cleaner design question [message #232692 is a reply to message #232539] |
Mon, 09 December 2013 09:39 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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I wish the guy I know with a flow bench was in my state. Would be cool to do empirical testing. Air cleaner in stock form, alone and on WOT Qjet, with and without dryer hose. Then do flipped lid, dual snorkel test, Jeep adaptor etc. This type of testing often gives unexpected results.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: Air cleaner design question [message #232695 is a reply to message #232692] |
Mon, 09 December 2013 10:27 |
 |
SeanKidd
Messages: 747
Registered: June 2012
Location: Northern Neck Virginia
Karma: 4
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Senior Member |
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Correct me if I'm wrong...This wouldn't need a big test stand to accomplish...an inline fan/ blower capable of producing CFM of engine, a speed controller( perhaps router speed control) some ducting, and a differential pressure meter...I can loan my digital DP meter if someone wants to attempt...
Set up fan as it were the carburetor, place a length of 3 or 4" PVC on it, perhaps 3' as a baseline, use speed control to dial in CFM;measure pressure drop.
Repeat with standard air cleaner and new filter
Repeat with snorkel and new filter
Sean and Stephanie
73 Ex-CanyonLands 26' #317 "Oliver"
Hubler 1-Ton, Quad-Bags, Rear Disc, Reaction Arms, P.Huber TBs, 3.70:1 LSD Honda 6500 inverter gen.
Colonial Travelers
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| Re: [GMCnet] Air cleaner design question [message #232696 is a reply to message #232645] |
Mon, 09 December 2013 10:50 |
habbyguy
Messages: 896
Registered: May 2012
Location: Mesa, AZ
Karma: 3
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Senior Member |
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| emerystora wrote on Sun, 08 December 2013 14:06 |
I don't see how you would get a bigger air flow using a 4 inch duct if you clamp it to the end of the stock air cleaner. The opening in the air cleaner nozzle is a lot smaller than 4" diameter so that restriction would moke the air flow the same.
|
The point was only to supply fresh, cool air TO the nose of the air cleaner. The 4" hose certainly won't restrict the air flow, and the fact that it's being fed by a scoop just behind the grille should mean that the air available at the nose of the air cleaner is not only cooler, but should be under at least a tiny bit of pressure compared to ambient air.
Mark Hickey
Mesa, AZ
1978 Royale Center Kitchen
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| Re: Air cleaner design question [message #232698 is a reply to message #232692] |
Mon, 09 December 2013 11:13 |
Bullitthead
Messages: 1411
Registered: November 2013
Karma: 5
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Senior Member |
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When I tried the Grand Cherokee intake duct on the Q-jet and it caused airflow disturbance, I went to the boneyard and obtained the 1 inch spacer from a GMC truck TBI and made it fit in between the duct and the carb. Airflow problems were solved! Unfortunately, I couldn't close the hood. I also had a 4 to 2 barrel adapter and an extra Ford PCV spacer on there to give me a longer intake runner to give a little more torque from a longer column of air. Removing one of those would give the necessary room for the hood, but they were required to adapt the Q-jet on top of the tiny intake manifold. I ended up using a marine backfire trap on it which will stop rocks and rags from getting in there, but won't stop fine dust.
All this experimentation was an effort to install a leaf blower on the intake to act as a supercharger. I got it all to work successfully without the hood on, but was not able to discern any difference in power output, so I gave up and just went back to the backfire trap. Just a little homebuilt engineering!
When I got the motorhome, the PO had installed an Edelbrock (actually a Weber)4V carb on there and a small air cleaner on there. The air filter element was smashed down to clear the floor. Didn't run right and really sucked the gas, so I removed the filter, but that didn't help. The 455 just didn't like that Weber, so I ended up putting my Q-jet from the Bronco on the GMC and put the Weber on the Bronco. Then I put the Bronco air cleaner on the GMC! All this musical parts swappage works very well now, but I have yet to climb a mountain at WOT in the GMC.
Terry Kelpien
ASE Master Technician
73 Glacier 260
Smithfield, Va.
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