Home » Public Forums » GMCnet » GMC STOCK CAST IRON INTAKE (What is best for our Motorhome intakes)
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| GMC STOCK CAST IRON INTAKE [message #352781] |
Sun, 15 March 2020 15:11  |
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Husker92592
Messages: 137
Registered: August 2013
Location: Temecula ca
Karma: -4
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So good afternoon, I hope that I am not to wordy my questioning, but just because our big blocks come with the the sunken stock 60# intake is it the correct choice for our coaches based on flow and reliability? There are plenty of aftermarket options that will of course trigger modifications but flow and technology on today's aftermarket options are they truly better?
At one time the Gary Rockwell aluminum option on bdub's site was in reach but not now as there is no link to purchase. It's difficult to throw $$$$$$ at an intake unless someone has a rational opinion on benefits to justify spending the cheddar. Running cooler in my mind is not a huge benefit unless other options come into play.
Increased flows or more efficient airflow
More torque
Fuel efficiency
Increased longevity
Performance
Maintenance
Exhaust crossover elimination
Is the stock iron manifold truly the right choice for fuel injection and our coaches based on current aftermarket intake technology/ choices?
If one really wanted to make interior changes on the coach Edelbrock, holley , offenhauser have "torquier" options for new intakes. So any of our .GM engineers have an opinion and then is there any justification to swap out our boat anchor for the $1,000.00 aluminum option? I have read multiple issues in the threads of the port lining up, must use a special gasket thickness for optimal alignment etc. to justify $1,000.00 investment?
As I have notice the trend from our GM engineers on the treads is don't mess with the original. So I suppose the stock cast iron intake is perfect?
Thanks for everyone's support.
1974 GMC Sequoia 26'
[Updated on: Sun, 15 March 2020 18:42] Report message to a moderator |
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| Re: GMC STOCK CAST IRON INTAKE [message #352786 is a reply to message #352781] |
Sun, 15 March 2020 18:14  |
lqqkatjon
Messages: 2324
Registered: October 2010
Location: St. Cloud, MN
Karma: 5
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Has everything to do with clearance. And little to do with performance.
The other variant is angle.
403 engines have more clearance. And 455 less. So if you are willing to raise your hatch, there are more options too.
Jon Roche
75 palm beach
EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
St. Cloud, MN
http://lqqkatjon.blogspot.com/
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| Re: GMC STOCK CAST IRON INTAKE [message #352791 is a reply to message #352781] |
Sun, 15 March 2020 20:13 |
Bullitthead
Messages: 1411
Registered: November 2013
Karma: 5
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I can't equate the combined gain of weight savings and any possible power or fuel economy increase with the $1K+ price for parts plus labor, so I would have to do it for fun. In that case, modding the interior would already have to be in the plans. Then just build the clear engine box and don't walk on it.
Terry Kelpien
ASE Master Technician
73 Glacier 260
Smithfield, Va.
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| Re: GMC STOCK CAST IRON INTAKE [message #352792 is a reply to message #352790] |
Sun, 15 March 2020 20:39 |
lqqkatjon
Messages: 2324
Registered: October 2010
Location: St. Cloud, MN
Karma: 5
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I am no expert, and maybe someone can put the engineering thoughts to the exact number. But my opinion there is very little to gain in performance by switching to any different manifolds. we run lower rpm, so really do not need huge flow. I am sure there is some improvement, but not sure it is worth anything. The reason to change manifolds is all based on other factors.
my observations, is that many of the original manifolds are coming up cracked. So the idea of new manifold is appealing. People install block off plates, and also fill the crossover, but if you can buy a new manifold, why not? last year I seen a stack of 7 cracked manifolds, and at that point the GMC'r decided to order up the aluminum one rather then keep trying to see if manifold #8 or 9 was any good.
I see many edlebrock performer manifolds installed. I have also seen people machining the carb surface to get it more level and also allow for a little more clearance.
if you want to stick with the stock air cleaner, clearance is an issue. The stock manifold and the aluminum one that seems to be now sourced through mondello, keep that profile so you have more clearance and should not need to raise the hatch of a 455 engine coach. Even with my EFI, clearance is very tight to get the remote air cleaner to fit. just having a little thinner adaptor plate made a difference.
Jon Roche
75 palm beach
EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
St. Cloud, MN
http://lqqkatjon.blogspot.com/
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| Re: [GMCnet] GMC STOCK CAST IRON INTAKE [message #352795 is a reply to message #352792] |
Sun, 15 March 2020 23:47 |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
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We supply the AL Intake manifold that is custom machined to fit the
Motorhome a
On Sun, Mar 15, 2020 at 6:51 PM Jon Roche via Gmclist <
gmclist@list.gmcnet.org> wrote:
> I am no expert, and maybe someone can put the engineering thoughts to the
> exact number. But my opinion there is very little to gain in performance
> by switching to any different manifolds. we run lower rpm, so really do
> not need huge flow. I am sure there is some improvement, but not sure it
> is worth anything. The reason to change manifolds is all based on other
> factors.
>
>
> my observations, is that many of the original manifolds are coming up
> cracked. So the idea of new manifold is appealing. People install block
> off
> plates, and also fill the crossover, but if you can buy a new manifold,
> why not? last year I seen a stack of 7 cracked manifolds, and at that point
> the GMC'r decided to order up the aluminum one rather then keep trying to
> see if manifold #8 or 9 was any good.
>
> I see many edlebrock performer manifolds installed. I have also seen
> people machining the carb surface to get it more level and also allow for a
> little more clearance.
>
> if you want to stick with the stock air cleaner, clearance is an issue.
> The stock manifold and the aluminum one that seems to be now sourced through
> mondello, keep that profile so you have more clearance and should not need
> to raise the hatch of a 455 engine coach. Even with my EFI, clearance
> is very tight to get the remote air cleaner to fit. just having a little
> thinner adaptor plate made a difference.
>
>
> --
> Jon Roche
> 75 palm beach
> EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
> St. Cloud, MN
> http://lqqkatjon.blogspot.com/
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
Jim Kanomata
Applied/GMC, Newark,CA
jimk@appliedairfilters.com
http://www.gmcrvparts.com
1-800-752-7502
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Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
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| Re: GMC STOCK CAST IRON INTAKE [message #352799 is a reply to message #352781] |
Mon, 16 March 2020 08:03 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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At the speed the engine turns in the coach - even with a short final drive ratio, you aren't going to gain much in performance changing intakes - there can be a weight savings of (someone said) 40 pounds over the stock iron one. To me, it ain't worth it. Swap if the original is cracked beyond repair or use.
--johnny
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: GMC STOCK CAST IRON INTAKE [message #352800 is a reply to message #352781] |
Mon, 16 March 2020 08:37 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Since 99% of driving is on the primary barrels of the Qjet, I would think a "high flow" manifold would reduce runner velocity and thereby reduce cylinder fill. Thereby reduce torque in the real world use scenario.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: [GMCnet] GMC STOCK CAST IRON INTAKE [message #352801 is a reply to message #352800] |
Mon, 16 March 2020 10:06 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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There is a reason that motorcycle engines, (high output ones, not modified
tractor engines like V-twins) use very short intake runners and a small
throated carb or fuel injector for each cylinder. It is because they
operate at amazing cfm compared to automotive applications. Large
bore/ultra short stroke by intentional design, they operate at unheard of
rpm's relative to automotive applications.
So, we have an Olds Toronado, and a Cadillac Eldorado. Front wheel
drive takes up all the under hood space that we normally use to lower the
engine in the compartment. Then, we can raise the plenums and achieve
better airflow through the intake passages.
I personally think that, given the low hood restraints, the drop
center intake does an adequate job of performing the task laid out for it.
High torque output at a very low rpm is a hard bugger to come by. Yet, that
cast iron behemoth does that job quite well. But, it cannot serve two
masters. You trade off high rpm performance for low end torque. In a
motorhome applications, that is EXACTLY what you want. Build your engine
around that specification, and you won't be sorry.
Jim Hupy
Salem, Oregon
On Mon, Mar 16, 2020, 6:59 AM John R. Lebetski via Gmclist <
gmclist@list.gmcnet.org> wrote:
> Since 99% of driving is on the primary barrels of the Qjet, I would think
> a "high flow" manifold would reduce runner velocity and thereby reduce
> cylinder fill. Thereby reduce torque in the real world use scenario.
> --
> John Lebetski
> Woodstock, IL
> 77 Eleganza II
>
>
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| Re: GMC STOCK CAST IRON INTAKE [message #352802 is a reply to message #352781] |
Mon, 16 March 2020 13:30 |
Bill Van Vlack
Messages: 419
Registered: September 2015
Location: Guemes Island, Washington
Karma: 14
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Once again, a great explanation Jim... thanks.
I understand that Mondello now has the pattern for the reproduction aluminum casting, so presumably any aluminum manifold procured for the last (two years?) would be from that source. I assume that Applied has added value by machining that casting to correct some (all?) of the fitment issues. Last I checked - about a year ago - Applied did not have any in stock. Presumably they do now, since they are being advertised on this thread.
Bill Van Vlack
'76 Royale; Guemes Island, Washington; Twin bed, full (DS) side bath, Brazilian Redwood counter and settee tops,455, 6KW generator; new owner a/o mid November 2015.
[Updated on: Mon, 16 March 2020 13:31] Report message to a moderator |
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| Re: [GMCnet] GMC STOCK CAST IRON INTAKE [message #352808 is a reply to message #352807] |
Mon, 16 March 2020 16:27 |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
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Great idea but someone need to come up with few thousand that will take
several years to pay back.
On Mon, Mar 16, 2020 at 2:13 PM Terry via Gmclist
wrote:
> Would be nice if someone made a cochlea type intake sunk into the intake
> valley like on late model V8s, and the corresponding valley pan to close
> that
> off and allow airflow under the intake. Long runners give even more torque
> at lower rpm. Really don't need to spin all those long rods and stuff past
> 4K in the GMC.
> Must be a CAD program for 3D printers that would allow matching
> runners of an existing manifold and virtually any head ports. Don't have
> computer
> powerful enough for that yet. Wouldn't know how to use program if I did.
> A recent retail development has maybe solved blocking off the exhaust
> cross ports using 3D printed metal on that valley pan. Haven't checked to
> see if there are already valley pans available for the OLDS, I'm sure
> there were in the past getting used mostly on drag boats and other toys...
> 8)
> The new intakes are made of plastic, wonder if they will last through
> 47 years of USE? A lot of the plastics made lately are degrading
> prematurely...planned obsolescence? Enviro-Engineering? Shoddy materials?
> Seen a lot of all three in the the past 8 years.
> --
> Terry Kelpien
>
> ASE Master Technician
>
> 73 Glacier 260
>
> Smithfield, Va.
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
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>
--
Jim Kanomata
Applied/GMC, Newark,CA
jimk@appliedairfilters.com
http://www.gmcrvparts.com
1-800-752-7502
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Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
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| Re: GMC STOCK CAST IRON INTAKE [message #352836 is a reply to message #352781] |
Tue, 17 March 2020 12:09 |
winter
Messages: 247
Registered: September 2007
Location: MPLS MN
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I've had an Edelbrock on the 77 403 for about 10 years. It fits well other than i think the AC support bracket for the A3 doesn't fit. That doesn't bother me though. I still intend to replace the old AC pump with a newer Sanden.
Don't use the edelbrock version of the crossover plugs. They don't fit the olds engine.
Jerrod Winter
1977 Palm Beach
Green Jelly Bean
Twin Cities, Minnesota
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| Re: [GMCnet] GMC STOCK CAST IRON INTAKE [message #352841 is a reply to message #352836] |
Tue, 17 March 2020 14:45 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Anyone considering using an Edelbrock intake manifold should pay close
attention to Jerrod's comment about the crossover plugs -- They do not work
-- AS INTENDED. They DO work to destroy cylinder heads -- see my
experience:
http://www.gmcmhphotos.com/photos/g3057-cylinder-head-damage-from-exhaust-crossover-plugs.html
I know of at least one case in which those plugs wore into the water
jacket, eventually causing a hydraulically locked and destroyed engine.
DON'T use loose medal blocks in the exhaust ports!!! (Even tho' Edelbrock
requires them for their warranty, last I saw.)
Ken H
On Tue, Mar 17, 2020 at 1:10 PM jerrod winter via Gmclist <
gmclist@list.gmcnet.org> wrote:
> I've had an Edelbrock on the 77 403 for about 10 years. It fits well
> other than i think the AC support bracket for the A3 doesn't fit. That
> doesn't
> bother me though. I still intend to replace the old AC pump with a newer
> Sanden.
>
> Don't use the edelbrock version of the crossover plugs. They don't fit
> the olds engine.
> --
> Jerrod Winter
> 1977 Palm Beach
> Green Jelly Bean
> Twin Cities, Minnesota
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
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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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