Does the OEM intake manifold have a common area under the carb ports

RF_Burns

Super Moderator
Staff member
Sep 7, 2008
5,141
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113
Ontario Canada
To clarify my question, after passing through the carb ports, does the air/fuel mixture enter a common area before going down the runners to the
various cylinders...?

The reason I ask, is to me it would make sense if the air/fuel mixture could mix from each port. That way if the A/F mixture was a bit lean from one
barrel, it would mix with air coming through the other barrel and even out the mixture a bit. If kept separate you could have 4 cylinders running
rich or worse 4 running lean.

With my EFI, the narrow-band O2 sensor is on only one exhaust manifold. So if the barrels are kept separate, one side would run at 14.7 AFR and the
other could be rich or lean. If that is the case, maybe I should put an O2 sensor on the other manifold with a circuit to switch back and forth
between the two cylinder banks.

If one of the injectors were to clog or become faulty, the fuel mixture would become lean going through that barrel of the Throttle Body. If there
was a common area below then the mixture would even out and the O2 sensor would compensate.

Or does each barrel feed 2 cylinders on each side of the engine which would mean my O2 sensor is seeing exhaust created by both barrels (injectors).

I have a wide-band sensor that is after the exhaust pipe Y and so samples from both banks. However sometimes it show richer and sometimes leaner
while the narrow-band shows it is switching so it is around 14.7.

Thanks!

--
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that
 
Bruce
The manifold on my 455 has an open chamber below the carb ports.

Dennis

> To clarify my question, after passing through the carb ports, does the air/fuel mixture enter a common area before going down the runners to the
> various cylinders...?
>
> The reason I ask, is to me it would make sense if the air/fuel mixture could mix from each port. That way if the A/F mixture was a bit lean from
> one barrel, it would mix with air coming through the other barrel and even out the mixture a bit. If kept separate you could have 4 cylinders
> running rich or worse 4 running lean.
>
> With my EFI, the narrow-band O2 sensor is on only one exhaust manifold. So if the barrels are kept separate, one side would run at 14.7 AFR and
> the other could be rich or lean. If that is the case, maybe I should put an O2 sensor on the other manifold with a circuit to switch back and forth
> between the two cylinder banks.
>
> If one of the injectors were to clog or become faulty, the fuel mixture would become lean going through that barrel of the Throttle Body. If
> there was a common area below then the mixture would even out and the O2 sensor would compensate.
>
> Or does each barrel feed 2 cylinders on each side of the engine which would mean my O2 sensor is seeing exhaust created by both barrels
> (injectors).
>
> I have a wide-band sensor that is after the exhaust pipe Y and so samples from both banks. However sometimes it show richer and sometimes leaner
> while the narrow-band shows it is switching so it is around 14.7p
>
> Thanks!

--
Dennis S
73 Painted Desert 230
Memphis TN Metro
 
I'm pretty sure the stock manifold is a dual plane. each side is separate.

________________________________
From: Gmclist on behalf of Bruce Hislop via Gmclist
Sent: Tuesday, January 12, 2021 7:52 PM
To: gmclist
Cc: Bruce Hislop
Subject: Re: [GMCnet] Does the OEM intake manifold have a common area under the carb ports

Thanks Dennis,
Saves me tearing stuff apart to get a look at mine.

--
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that

_______________________________________________
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Bruce
I don’t think I described the intake very well or correctly.
Here are photos of the intake being reverse engineered - which better shows how the ports feed the intake runners.

Dennis

http://www.gmcmhphotos.com/photos/gmc-intake-manifold-project/p8298.html

> Bruce
> The manifold on my 455 has an open chamber below the carb ports.
>
> Dennis
>

> > To clarify my question, after passing through the carb ports, does the air/fuel mixture enter a common area before going down the runners to
> > the various cylinders...?
> >
> > The reason I ask, is to me it would make sense if the air/fuel mixture could mix from each port. That way if the A/F mixture was a bit lean
> > from one barrel, it would mix with air coming through the other barrel and even out the mixture a bit. If kept separate you could have 4
> > cylinders running rich or worse 4 running lean.
> >
> > With my EFI, the narrow-band O2 sensor is on only one exhaust manifold. So if the barrels are kept separate, one side would run at 14.7 AFR
> > and the other could be rich or lean. If that is the case, maybe I should put an O2 sensor on the other manifold with a circuit to switch back and
> > forth between the two cylinder banks.
> >
> > If one of the injectors were to clog or become faulty, the fuel mixture would become lean going through that barrel of the Throttle Body. If
> > there was a common area below then the mixture would even out and the O2 sensor would compensate.
> >
> > Or does each barrel feed 2 cylinders on each side of the engine which would mean my O2 sensor is seeing exhaust created by both barrels
> > (injectors).
> >
> > I have a wide-band sensor that is after the exhaust pipe Y and so samples from both banks. However sometimes it show richer and sometimes
> > leaner while the narrow-band shows it is switching so it is around 14.7p
> >
> > Thanks!

--
Dennis S
73 Painted Desert 230
Memphis TN Metro
 
I agree with Keith. I have an intake manifold soaking in my parts washer, but I will not be out there for several days to look at it. If you do not
get a definitive answer, send me a PM or and email note to remind me and I will look at mine. I once had a carb that was dumping excess fuel on one
side. It caused the excess fuel to end up in the muffler which burned there and crystallized metal case of the muffler. That eventually burned a
hole the size of a soft ball in the top of it. So I believe the two sides do not mix or mix very well.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
The throats in the OEM intake manifold are definitely separate. One serves
two cylinders on the right bank and two on the left bank. The other serves
the remaining cylinders on each bank. There are small passages between the
two sides in the base of the carburetor, and due to the exhaust crossover
there are frequently hairline cracks in the divider between the two
throats; they don't allow much flow between the two.

Ken H.

On Wed, Jan 13, 2021 at 6:09 AM Ken Burton via Gmclist <

> I agree with Keith. I have an intake manifold soaking in my parts washer,
> but I will not be out there for several days to look at it. If you do not
> get a definitive answer, send me a PM or and email note to remind me and I
> will look at mine. I once had a carb that was dumping excess fuel on one
> side. It caused the excess fuel to end up in the muffler which burned
> there and crystallized metal case of the muffler. That eventually burned a
> hole the size of a soft ball in the top of it. So I believe the two sides
> do not mix or mix very well.
> --
> Ken Burton - N9KB
> 76 Palm Beach
> Hebron, Indiana
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
 
Dennis,
Thank-you! Those were the photos I was looking for to answer my question.

Ken Burton, My answer is in these photos.

http://www.gmcmhphotos.com/photos/gmc-intake-manifold-project/p8298.html

Since each carb port feeds 2 cylinders on each side, that takes care of my concern that my O2 sensor would not pick up on a faulty injector. The
sensor will get a sample of the exhaust created by either injector.

In case of a partially clogged injector, the O2 would see a leaning condition and increase the fuel flow. However 4 cylinders would be rich and the
other 4 would be lean, but not as lean as it would be otherwise.

Thanks guys.

--
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that
 
Dennis,

Thanks for the link. That is a wonderful display of what it takes to create an V-pattern intake.

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
 
Is it worth the effort to make a modern fuel injection manifold with injection for each individual cylinder for the 455?

Randy Hecht
Roswell, GA

1974 Canyon Lakes GMC Motor-coach

>
> Dennis,
>
> Thanks for the link. That is a wonderful display of what it takes to create an V-pattern intake.
>
> 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
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
 
Randy,

Someone already has but I believe it quite expensive.

Sully
Bellevue wa

On Wed, Jan 13, 2021 at 7:54 AM Randy Hecht via Gmclist <

> Is it worth the effort to make a modern fuel injection manifold with
> injection for each individual cylinder for the 455?
>
> Randy Hecht
> Roswell, GA
>
> 1974 Canyon Lakes GMC Motor-coach
>
>
> > On Jan 13, 2021, at 10:08, Matt Colie via Gmclist <

> >
> > Dennis,
> >
> > Thanks for the link. That is a wonderful display of what it takes to
> create an V-pattern intake.
> >
> > 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
> >
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
 
It's going to become necessary to start doing multiport injection at some point. Big block TBI units are getting hard to come by.

BTW, the Dynamic EFI can run multiport fuel injection with the port mod ($25) But I'm not sure what you would use for the throttle body, maybe a gutted quadrajet?

Keith Vasilakes
Mounds View MN
76 exRoyale
MicroLevelhttp://www.gmcmotorhomemarketplace.com/vasilakes/microlevel_intro.pdf

The biggest hurdle would probably be the fuel rails and intake manifold machining
________________________________
From: Gmclist on behalf of Todd Sullivan via Gmclist
Sent: Wednesday, January 13, 2021 9:58 AM
To: gmclist
Cc: Todd Sullivan
Subject: Re: [GMCnet] Does the OEM intake manifold have a common area under the carb ports

Randy,

Someone already has but I believe it quite expensive.

Sully
Bellevue wa

On Wed, Jan 13, 2021 at 7:54 AM Randy Hecht via Gmclist <

> Is it worth the effort to make a modern fuel injection manifold with
> injection for each individual cylinder for the 455?
>
> Randy Hecht
> Roswell, GA
>
> 1974 Canyon Lakes GMC Motor-coach
>
>
> > On Jan 13, 2021, at 10:08, Matt Colie via Gmclist <

> >
> > Dennis,
> >
> > Thanks for the link. That is a wonderful display of what it takes to
> create an V-pattern intake.
> >
> > 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
> >
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
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Unsubscribe or Change List Options:
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I saw a multi port fuel injection system on a coach at Coos Bay several
years ago. He had the aluminum 455 MH intake which had been bored for fuel
injectors at each port. I believe he was running it with the ebl. Don’t
remember what was sitting where the carb usually lives.

Sully
Bellevue wa

On Wed, Jan 13, 2021 at 10:42 AM Keith V via Gmclist <

> It's going to become necessary to start doing multiport injection at some
> point. Big block TBI units are getting hard to come by.
>
> BTW, the Dynamic EFI can run multiport fuel injection with the port mod
> ($25) But I'm not sure what you would use for the throttle body, maybe a
> gutted quadrajet?
>
> Keith Vasilakes
> Mounds View MN
> 76 exRoyale
> MicroLevel<
> http://www.gmcmotorhomemarketplace.com/vasilakes/microlevel_intro.pdf>
>
>
> The biggest hurdle would probably be the fuel rails and intake manifold
> machining
> ________________________________
> From: Gmclist on behalf of Todd
> Sullivan via Gmclist
> Sent: Wednesday, January 13, 2021 9:58 AM
> To: gmclist
> Cc: Todd Sullivan
> Subject: Re: [GMCnet] Does the OEM intake manifold have a common area
> under the carb ports
>
> Randy,
>
> Someone already has but I believe it quite expensive.
>
> Sully
> Bellevue wa
>
> On Wed, Jan 13, 2021 at 7:54 AM Randy Hecht via Gmclist <

>
> > Is it worth the effort to make a modern fuel injection manifold with
> > injection for each individual cylinder for the 455?
> >
> > Randy Hecht
> > Roswell, GA
> >
> > 1974 Canyon Lakes GMC Motor-coach
> >
> >
> > > On Jan 13, 2021, at 10:08, Matt Colie via Gmclist <

> > >
> > > Dennis,
> > >
> > > Thanks for the link. That is a wonderful display of what it takes to
> > create an V-pattern intake.
> > >
> > > 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
> > >
> > > _______________________________________________
> > > GMCnet mailing list
> > > Unsubscribe or Change List Options:
> > > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
> >
> >
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
> >
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
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>
 
> Is it worth the effort to make a modern fuel injection manifold with injection for each individual cylinder for the 455?
>
> Randy Hecht
> Roswell, GA
> 1974 Canyon Lakes GMC Motor-coach

Randy,

As I did do this very thing for three (maybe four - it was a long time ago), I can tell you that the advantage is only for emissions, and nothing
else. There are more than a few engines running stereo egos and trimming the mixture on an individual cylinder basis. This is only a marginal
benefit and even then only on some points of operation.

If the intent is to do this after the TBI parts go short, remember that there are lots of BBChevs in trucks that will not be replaced until they have
to be. More than that, the 8.1 family is only recently discontinued and that can be another source.

I refuse to worry about it.

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
 
Thank you for the info.

Randy Hecht
Roswell, GA

1974 Canyon Lakes GMC Motor-coach

>

>> Is it worth the effort to make a modern fuel injection manifold with injection for each individual cylinder for the 455?
>>
>> Randy Hecht
>> Roswell, GA
>> 1974 Canyon Lakes GMC Motor-coach
>
> Randy,
>
> As I did do this very thing for three (maybe four - it was a long time ago), I can tell you that the advantage is only for emissions, and nothing
> else. There are more than a few engines running stereo egos and trimming the mixture on an individual cylinder basis. This is only a marginal
> benefit and even then only on some points of operation.
>
> If the intent is to do this after the TBI parts go short, remember that there are lots of BBChevs in trucks that will not be replaced until they have
> to be. More than that, the 8.1 family is only recently discontinued and that can be another source.
>
> I refuse to worry about it.
>
> 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
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
 
Multi point fuel injection comes with it's own set of problems. The larger
number of injectors that you have, the more likely that you will have a
problem with one or more of them. If you plug up an injector, the engine
will still run. If you are working it hard, you will more than likely cause
some serious damage inside that cylinder.
The aftermarket aluminum manifold made for the 455 has cast in bosses
that can be bored out to accommodate common sized injector bodies. The air
horn assembly can be a Holley or a GM common rail valve body. The Howell
EBL can be programmed to run multipoint. There are several GMCERS out there
running a similar system.
One final caution which you are likely to already be aware of, is the
more complex a system is, the more troublesome it will be. It comes down to
benefits of complex systems vs simplicity of a quadrajet. Be careful what
you wish for, you are just likely to get it. (Grin)
Jim Hupy
Salem, Oregon

On Wed, Jan 13, 2021, 1:24 PM Randy Hecht via Gmclist <

> Thank you for the info.
>
> Randy Hecht
> Roswell, GA
>
> 1974 Canyon Lakes GMC Motor-coach
>
>
> > On Jan 13, 2021, at 15:34, Matt Colie via Gmclist <

> >

> >> Is it worth the effort to make a modern fuel injection manifold with
> injection for each individual cylinder for the 455?
> >>
> >> Randy Hecht
> >> Roswell, GA
> >> 1974 Canyon Lakes GMC Motor-coach
> >
> > Randy,
> >
> > As I did do this very thing for three (maybe four - it was a long time
> ago), I can tell you that the advantage is only for emissions, and nothing
> > else. There are more than a few engines running stereo egos and
> trimming the mixture on an individual cylinder basis. This is only a
> marginal
> > benefit and even then only on some points of operation.
> >
> > If the intent is to do this after the TBI parts go short, remember that
> there are lots of BBChevs in trucks that will not be replaced until they
> have
> > to be. More than that, the 8.1 family is only recently discontinued and
> that can be another source.
> >
> > I refuse to worry about it.
> >
> > 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
> >
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
 
Keep It Simple is my way, it’s a lot easier.
I like carburetors be cause I can work on them, fuel injection was what does the future bring into play thought.

-----Original Message-----
From: Gmclist On Behalf Of James Hupy via Gmclist
Sent: Wednesday, January 13, 2021 5:10 PM
To: gmclist
Cc: James Hupy
Subject: Re: [GMCnet] Does the OEM intake manifold have a common area under the carb ports

Multi point fuel injection comes with it's own set of problems. The larger number of injectors that you have, the more likely that you will have a problem with one or more of them. If you plug up an injector, the engine will still run. If you are working it hard, you will more than likely cause some serious damage inside that cylinder.
The aftermarket aluminum manifold made for the 455 has cast in bosses that can be bored out to accommodate common sized injector bodies. The air horn assembly can be a Holley or a GM common rail valve body. The Howell EBL can be programmed to run multipoint. There are several GMCERS out there running a similar system.
One final caution which you are likely to already be aware of, is the more complex a system is, the more troublesome it will be. It comes down to benefits of complex systems vs simplicity of a quadrajet. Be careful what you wish for, you are just likely to get it. (Grin) Jim Hupy Salem, Oregon

> Thank you for the info.
>
> Randy Hecht
> Roswell, GA
>
> 1974 Canyon Lakes GMC Motor-coach
>
>
> > On Jan 13, 2021, at 15:34, Matt Colie via Gmclist <

> >

> >> Is it worth the effort to make a modern fuel injection manifold
> >> with
> injection for each individual cylinder for the 455?
> >>
> >> Randy Hecht
> >> Roswell, GA
> >> 1974 Canyon Lakes GMC Motor-coach
> >
> > Randy,
> >
> > As I did do this very thing for three (maybe four - it was a long
> > time
> ago), I can tell you that the advantage is only for emissions, and
> nothing
> > else. There are more than a few engines running stereo egos and
> trimming the mixture on an individual cylinder basis. This is only a
> marginal
> > benefit and even then only on some points of operation.
> >
> > If the intent is to do this after the TBI parts go short, remember
> > that
> there are lots of BBChevs in trucks that will not be replaced until
> they have
> > to be. More than that, the 8.1 family is only recently discontinued
> > and
> that can be another source.
> >
> > I refuse to worry about it.
> >
> > 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
> >
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
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A manifold that is all common runners will have poor low speed torque characteristics as pulses are less discrete.
--
John Lebetski
Woodstock, IL
77 Eleganza II
 
On a stock setup when you lean an idle mixture screw, you are only leaning 4 cylinders. That’s why it’s a bit of an art to adjust, wait, go to
other side, repeat, etc.
--
John Lebetski
Woodstock, IL
77 Eleganza II