Home » Public Forums » GMCnet » Please help with air cleaner advice/info
| Please help with air cleaner advice/info [message #173340] |
Thu, 14 June 2012 18:30  |
glacierfl
Messages: 444
Registered: June 2011
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Hello,
I am getting around to refitting the air cleaner. My old one was broken, and a kind person sent me one. When it arrived, i noticed a part looks like a filter that had been damaged.
I have some photos on this link.
http://www.gmcmhphotos.com/photos/member-galleries/p44519-af1.html
I do not know what the devices and things on the air cleaner do.
Can all the stuff be replaced. I would like to get it sand blasted etc, and fit new stuff if possible. It would look nice then, 'ok i know its only cosmetic but....' Can you get new air cleaners i have looked around but no luck there.
Your help would be very much appreciated. Thank you.
cheers and beers
Steve & Debbie
Monticello, FL
77 Palm Beach :- Aurora
EX G4WDT
[Updated on: Thu, 14 June 2012 22:21] Report message to a moderator |
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| Re: Please help with air cleaner advice/info [message #173348 is a reply to message #173343] |
Thu, 14 June 2012 20:30  |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
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The big tube goes between the driver's side valve cover and the side of the air cleaner. The little tube goes to any available vacuum source. It is usually attached to the intake manifold vacuum source just to the rear of the carburetor. That small filter goes inside of the air cleaner where the big tube attaches.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: Please help with air cleaner advice/info [message #173356 is a reply to message #173348] |
Thu, 14 June 2012 22:38 |
glacierfl
Messages: 444
Registered: June 2011
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Hello,
Cool on the filter, now i know what it is, where it goes and also it needs a clip to attach it. I am much wiser now  I shall go get those this weekend.
As i mentioned previously my old one was basically broken. The postal service, managed to break the filter off, so i did not know where it was supposed to go. The clip must have fallen out of the package, as it was torn... so i did not know it needed a clip.
'Does anyone know how to test the actuator', and what effect might it have if its not working.
Not being an engine guy, i guess it controls the flow of air into the engine, using vacuum and temperature to modify as needed... Well bit by bit i am getting to know about the engine etc, maybe one day i will be able to help someone on here.
cheers and beers
Steve & Debbie
Monticello, FL
77 Palm Beach :- Aurora
EX G4WDT
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| Re: Please help with air cleaner advice/info [message #173358 is a reply to message #173340] |
Fri, 15 June 2012 01:11 |
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John Heslinga
Messages: 632
Registered: February 2011
Location: Edmonton, Alberta, Canada
Karma: 4
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Steve:
May I explain:
1. The Small Filter in the Air cleaner is a part of the PCV (Positive Crankcase Ventilation), system. (I Know it was said already: However, there is more). The PCV Valve (Between the right Valve Cover and the base of the carburetor) applies a controlled amount of manifold vacuum to the the crankcase on one side of the engine. The purpose is to suck crankcase gases, and combustion blow-by into the engine for burning. Fresh air is drawn into the other side of the engine valve cover through the pipe and air cleaner assembly. Because in some applications the fitting is on the unfiltered side of the air filter in the air cleaner, this filter is used for some applications. (There are other strategies used as well.) But there is more to the PCV System. The air flow goes from air cleaner to carburetor only while there is higher vacuum. During Wide Open throttle there is very little vacuum and there is a lot of crankcase gasses being produced because of the high revs and high combustion pressures. Now the Air cleaner has some vacuum and the Air flow is reversed and the crankcase gases are now expelled into the air cleaner and carburetor to be burned . Because of the higher revs, there is usually more oil mist in the crank case vapours as well. The filter in the Air cleaner now traps the oil mist so that it can be returned to the PCV System when the vacuum returns. BUT!!! our GMCs do not use the filter in the air cleaner. There is a filter and screen in the Black Valve cover fitting that fits into the rubber grommet.. (Few people know this and never service it) . That being said however , you may need to get the filter just so you can hook up the hose to that air cleaner you have. You can remove the filter element from the plastic case or just leave it there it will not hurt. These filters are readily available at most parts stores any the clips usually come with it. (At least they used to and I used to when I had AC in stock). Be careful that when you buy the filter, you get one with the plastic, some are just the element. Ask the parts person.
2. The Air Cleaner also pre-heats intake air. Whenever the air entering the air cleaner is below a certain temperature, the controls will close the damper door in the snorkel to direct air heated by the exhaust manifold into the air cleaner. There should be a duct that comes from the exhaust manifold oven to the bottom of the Air cleaner snorkel. Unfortunately, I do not know what temperature is the switching point, I would have to look it up. The Vacuum valve near the centre of the air cleaner opens whenever temperatures are below the set temperature. When the valve is open it applies vacuum to the vacuum motor (diaphragm) in the snorkel. The link moves the air valve to close the cold air and open warm air from the exhaust manifold oven. The parts of that system are really pretty robust and you will not likely need to be replaced. If you do need parts they can be acquired, but it will take some effort. The Vacuum supply to the temperature valve must come from a vacuum source with constant vacuum on the intake manifold. Do not connect to just any vacuum line coming from the carburetor. Some of those lines are ported vacuum used for different purposes. Check the opening temperature of the valve by applying a vacuum with a tester and use ice cubes to cool it down. It should open at some point and release the vacuum. The motor can be checked by applying vacuum directly to the motor and see that it moves the dampers and will hold a vacuum.
3. By the way; Check that the base actually allows you to point the snorkel in the right direction. There is a key stamped into the base that may need to be adapted. Also check your Motor cover for clearance.
4. Put the base on your carb and ensure that it does not interfere with anything. (Distributor, Throttle, Accelerator pump, ) While I don't suspect you will have any problems, remember that it does come from a different application, and you don't want to refinish it only to find there is a problem.
Good Luck
John Heslinga
John and Cathie Heslinga
1974 Canyonlands 260
455, Manny tranny and 1 ton, 3:70 LS,
Red Seal Journeyman, DTE, BEd. MEd.
Edmonton, Alberta
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| Re: Please help with air cleaner advice/info [message #173360 is a reply to message #173359] |
Fri, 15 June 2012 02:39 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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All of what John said is true but probably unnecessary for your GMC application. I do not even have the snorkel on my air cleaner. I have a hose direct from the air cleaner run up front to the grill to bring is as much cool and ram air as possible. I have no air valve (that part was mounted o the removed snorkel) and the temperature sensor is not hooked up to vacuum since there is no valve to control.
The purpose of that valve and temp sensor was primarily to prevent carburetor icing. Carb icing occurs at intake air temperatures of temperatures of 32 to 38 degrees F in humid conditions. GMCs with headers do not even have the baffles to collect warm air to go through that air valve.
So I would just install it, hook up the hoses and be done with it.
I do not know if it also has some emission ramifications.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: Please help with air cleaner advice/info [message #173361 is a reply to message #173360] |
Fri, 15 June 2012 05:08 |
glacierfl
Messages: 444
Registered: June 2011
Karma: 0
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Hello,
Ken you are saying that running it with that stuff disconnected has no adverse affect on the engine?.
Have looking up stuff, and find it is a Thermostatic air cleaner 'THERMAC'. Seems most parts are available, does not look like the part #6484245 is available. Thats the part on the nozzle that blocks the airflow into the air cleaner.
Someone had a new fitment in a box on ebay, but the auction ended. I would like to get it back to new, i will try autozone etc this weekend, but i doubt that part is gonna show up. So if anyone has that part new, that is surplus to requirements, please let me know.
cheers and beers
Steve & Debbie
Monticello, FL
77 Palm Beach :- Aurora
EX G4WDT
[Updated on: Fri, 15 June 2012 05:10] Report message to a moderator |
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| Re: [GMCnet] Please help with air cleaner advice/info [message #173368 is a reply to message #173358] |
Fri, 15 June 2012 07:19 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Senior Member |
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John,
Thanks for that review of the air filter operation. I think you've
answered most of the question I've been meaning to ask: I've always had
some oiling of the air filter element and, especially the throttle body,
from the left side valve cover hose. It's been worse with the 500 than
with the 455.
Just a few days ago, cleaning up the new engine installation, I examined
the rocker cover-to-hose adapter (it's a much larger, rectangular, device
on the 500) and found that it was just an empty can -- not even any baffles
in it. Whether it ever had anything inside it, I don't know, but that
seemed to me a rather useless "oil separator". Not knowing what else to
do, I stuffed a whole SS scrub pad into it through one of the holes. That
was not as difficult as I'd expected -- I rolled it into a wiener shape
first, then as it bunched up forced it in with a screwdriver. Compressed
air blown through it didn't dislodge any particles so I'm not worried about
polluting the engine. There was no noticeable resistance when I blew
through it bby mouth, so I don't think it will do any harm.
I'm hoping the filtering action of the vastly increased surface area will
reduce my oil mist flow into the air cleaner and TB.
Does anyone know if there would have been some sort of filler in the
adapter back in '72 when it was made?
Ken H.
On Fri, Jun 15, 2012 at 2:11 AM, John Heslinga wrote:
... During Wide Open throttle there is very little vacuum and there is a
lot of crankcase gasses being produced because of the high revs and high
combustion pressures. Now the Air cleaner has some vacuum and the Air flow
is reversed and the crankcase gases are now expelled into the air cleaner
and carburetor to be burned . Because of the higher revs, there is usually
more oil mist in the crank case vapours as well. The filter in the Air
cleaner now traps the oil mist so that it can be returned to the PCV System
when the vacuum returns...
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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| Re: Please help with air cleaner advice/info [message #173373 is a reply to message #173340] |
Fri, 15 June 2012 08:48 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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The target temp according to explanation in GM service manuals was 115F. The mix door would try to achieve that and then open wide at WOT when vac fell off. That air cleaner is from a OLDS but appears a slightly differnet model than the motorhome. The MH unit had the snorkle for a cold air hose and it looks like maybe the clockposition on your snorkle is slightly more towards 9 O'Clock and the MH was more at 10 O'Clock. Also the MH used the round metal breather filter at the valve cover not the one in the cleaner housing. SOOOO, you may have some slight fitment issues. I tryed to paste a pic of the GM breather but too large to attach here. Same used on many Olds powered and the Buick VIN7 Turbo cars 1986 and 87.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: [GMCnet] Please help with air cleaner advice/info [message #173376 is a reply to message #173361] |
Fri, 15 June 2012 08:50 |
powerjon
Messages: 2446
Registered: January 2004
Karma: 5
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Senior Member |
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Steve,
I did the same as Ken when it came to the air cleaner. Except for the
PCV valve air line to the valve cover I disconnected and/or removed
all stuff off the air cleaner base. I also cut most of the snorkel
off and ran 4" air ducting up front to bring in fresh cold air to the
engine making is a cold air package. All the new engines from the new
cars dealers run cold air to the engine, go look under the hood of
your car. I would not spend any money trying to buy any replacement
parts as they are really not necessary to run the engine.
Here is an example, there are many more
<http://www.gmcmhphotos.com/photos/mechanical/p34218-cold-air-intake-from-grill.html
>
<http://www.gmcmhphotos.com/photos/mechanical/p34220-cold-air-intake-from-grill.html
>
JR Wright
GMC Great Laker MHC
GMC Eastern States
GMCMHI
78 Buskirk 30' Stretch
1975 Avion (Under Reconstruction)
Michigan
>
>
> Hello,
> Ken you are saying that running it with that stuff disconnected has
> no adverse affect on the engine?.
>
> Have looking up stuff, and find it is a Thermostatic air cleaner
> 'THERMAC'. Seems most parts are available, does not look like the
> part #6484245 is available. Thats the part on the nozzle that blocks
> the airflow into the air cleaner.
>
> Someone had a new fitment in a box on ebay, but the auction ended. I
> would like to get it back to new, i will try autozone etc this
> weekend, but i doubt that part is gonna show up. So if anyone has
> that part new, please let me know.
>
>
>
>
> --
> Steve & Debbie
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J.R. Wright
GMC GreatLaker
GMC Eastern States
GMCMI
78 30' Buskirk Stretch
75 Avion Under Reconstruction
Michigan
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| Re: [GMCnet] Please help with air cleaner advice/info [message #173379 is a reply to message #173376] |
Fri, 15 June 2012 09:49 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Senior Member |
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Steve, there is one exception kinda missed by those fellows who recommend
removing the air diverter in the snorkle. I concur that colder, denser air
has the potential to produce more horsepower, particularly when the
carburetor mixture is a little rich. But, as I have read the C.A.R.B.
propaganda, it states that the engine must have in place all the equipment
originally fitted to that specific application in order to pass smog
certification, or the replacement parts must be C.A.R.B. certified. This
applies in California, and other copy cat states as well. Things like PCV
valves, EGR equipment, AIR systems, Charcoal Cannisters, Vacuum Retard
cannisters on the distributor, are all listed, dependent upon year model.
But, it is your GMC. Do what pleases you, except in california. We here in
oregon have a saying that was attributed to Governor Tom McCall. "Don't
Californicate Oregon." <Grin>
Jim Hupy
Salem, OR
78 GMC Royale 403
On Fri, Jun 15, 2012 at 6:50 AM, John Wright <powerjon@chartermi.net> wrote:
> Steve,
> I did the same as Ken when it came to the air cleaner. Except for the
> PCV valve air line to the valve cover I disconnected and/or removed
> all stuff off the air cleaner base. I also cut most of the snorkel
> off and ran 4" air ducting up front to bring in fresh cold air to the
> engine making is a cold air package. All the new engines from the new
> cars dealers run cold air to the engine, go look under the hood of
> your car. I would not spend any money trying to buy any replacement
> parts as they are really not necessary to run the engine.
>
> Here is an example, there are many more
>
> <
> http://www.gmcmhphotos.com/photos/mechanical/p34218-cold-air-intake-from-grill.html
> >
>
> <
> http://www.gmcmhphotos.com/photos/mechanical/p34220-cold-air-intake-from-grill.html
> >
>
> JR Wright
> GMC Great Laker MHC
> GMC Eastern States
> GMCMHI
> 78 Buskirk 30' Stretch
> 1975 Avion (Under Reconstruction)
> Michigan
>
>
>
> >
> >
> > Hello,
> > Ken you are saying that running it with that stuff disconnected has
> > no adverse affect on the engine?.
> >
> > Have looking up stuff, and find it is a Thermostatic air cleaner
> > 'THERMAC'. Seems most parts are available, does not look like the
> > part #6484245 is available. Thats the part on the nozzle that blocks
> > the airflow into the air cleaner.
> >
> > Someone had a new fitment in a box on ebay, but the auction ended. I
> > would like to get it back to new, i will try autozone etc this
> > weekend, but i doubt that part is gonna show up. So if anyone has
> > that part new, please let me know.
> >
> >
> >
> >
> > --
> > Steve & Debbie
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
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| Re: Please help with air cleaner advice/info [message #173389 is a reply to message #173340] |
Fri, 15 June 2012 12:19 |
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John Heslinga
Messages: 632
Registered: February 2011
Location: Edmonton, Alberta, Canada
Karma: 4
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Senior Member |
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Ken:
Good Plan on the Stainless Steel Scrubbie, I'm sure it will work fine. After-Market and custom Breathers such as Mr Gasket use similar fillers to catch the mist and they work pretty good too. If you look into the GMC breather the filtering media is between screens. I suspect the filtering media in those is very different and they ensure breaking down media does not pollute the engine.
Steve:
If you need that Vacuum Motor on the snorkel, it is available from a number of sources other than the dealer. I find that the problem is getting a parts person to spend some time looking for you. I've found so many parts by asking for the paper catalogues and some time at the end of the counter. (I've been a parts person myself so I have some of the skills to find these things. (Most are kids who only know how to fill in the blanks for the computer, and the computer only looks up parts in one way. On line catalogues are too limited as well.)
Here is one on line source for that motor.
www.thepartsplaceinc.com
lookup part #CW8422Z $19.00.
You will find that the metal link is straight and needs to be bent to match yours so the vacuum fitting goes in the right direction.
As far a C.A.R.B. Goes : The Doug Thorley headers sold by the suppliers are C.A.R.B approved and come with a fitting that is clamped to the front header pipe as a heat oven to connect the preheat tube for the air cleaner. This will make the system CARB complient.
Everyone:
The following is probably a discussion starter I suppose.
The way the system was designed on my 74, indicates that this is not just for cold starting as might be expected or for just early fuel vaporization. Otherwise it would have a temp / Vac Valve in the cooling Jacket to block vac supply to the air cleaner temp sensor when engine temperatures are high enough. These were put in place in later model vehicles, but I'm not sure of the GMC.
The ThermAC purpose is keeping intake air temperature above the set-point of the temp / Vac Valve at all times because the vacuum source is not controlled. If that is the case, and if the the set point is 114 degrees, as stated here, then a cold air hose to the front will be closing and opening by the system in short cycles. This cycling would defeat most of the benefits of the cold and Ram Air effect in an unmodified system. That would be why some have disabled this air pre-heat system. Disabling this system will not cause any problems in most cases. Like any modification however, you might find some minor driveability issues in some conditions.
All of this said: I, and a lot of others, have highly modified engines and systems and have worked out, or live with some of these minor issues. If you want to make changes, by all means go ahead, however you need to understand the relationships. Here is a picture of my engine in the engine bay.
http://www.gmcmhphotos.com/photos/member-galleries/p44526-engine-top-view.html
You will notice that I do not have a stock Air Cleaner. This one looks great but I will be changing it to a more stock configuration. Another purpose of the Air Cleaner is to Muffle Intake noises and this one is just too loud and will not allow me to use the cold / Ram Air ducting.
Best Regards
John and Cathie Heslinga
1974 Canyonlands 260
455, Manny tranny and 1 ton, 3:70 LS,
Red Seal Journeyman, DTE, BEd. MEd.
Edmonton, Alberta
[Updated on: Fri, 15 June 2012 12:21] Report message to a moderator |
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| Re: Please help with air cleaner advice/info [message #173394 is a reply to message #173340] |
Fri, 15 June 2012 13:26 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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This is a carry over from the car side of GM for drivability and emissions and is "less of an issue" on a 10,000# vehicle generating a lot of heat. This is still of value during warm up and cold weather driving. Long warm up times once thought to be good for an engine have now been documented bad. Best is to start up and drive off gently. Long idle warmup just puts more water in the oil. I think the Themac does give better mileage/drivability due to better fuel assimilation on cool/cold days and allows for the leaner setup. At WOT it's a non factor. Don't confuse carburetor technolgy with modern EFI where there are induction air temp sensors and "cold air all the time" is the rule as fuel can be adjusted on a dime.
John Lebetski
Woodstock, IL
77 Eleganza II
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