G.M.C. Stromberg Carb.

[D.R.H.]

Hey Gents, I was lucky to find this Intake/Exhaust Manifold with Stromberg WW Carburetor. Does anyone happen to know the C.F.M. flow of this Carb.?
This assembly came from either the M-135 or M-211. The date on the intake is 1953.







Thanks.

[Joe Gopan]

Note the intake has the large ports and will not match up to pre 1953 270. M-211/M-135 used a Holley Carburetor. Have an idea that this is not a Military set up. If I have a Stronberg Book it will be a GI TM. Will look to see if I have a Stromberg book later today.

[Dr Deuce]

The 302 engines had 2 different manifolds. The flat runner one as shown and the round runners. The civy engines had a 3 bolt Holley 2bbl or a 4 bolt Stromberg 2bbl used on the later round runner manifolds. As Ben stated, you will be very had pressed to get the intake manifold to seal and keep it sealed to a pre 53 head with the different sized ports where you cannot use the centering rings. That manifold I believe came off of a Low Cab Forward truck due to the linkage on the manifold for the throttle linkage. I seem to remember seeing that linkage on one of my 302 civy engines. The military trucks used the 4 bolt rounded runners manifold.

[D.R.H.]

Thanks guys, you are both correct about the intake manifold. It is indeed the large port intake, BUT, there won't be any issue at all when it comes to mating up with the 302 cylinder head that is installed on the engine. You see when I rebuilt it, I changed several things about the engine internally. It has a high performance cam of 440 lift and 276 duration. Flat top aluminum pistons that are .030" over stock size. The head has been fly-cut -.100" to bring the compression up from 6.6 to 1, to 8.3 to 1. The original 270 head was badly cracked in several areas, so it went into the round file. You should know me by now Ben, I like an engine with bit more guts than the stock 99 H.P.
So Dr. Deuce, what is this "round runner" you speak of. I am not aware of this term. Education is welcomed.

These two photos are of the intake and exhaust that I personally removed from the junk M-211. It did not have the Holley 2 bbl. carb. that Ben was talking about so, I had to resort to this Ball & Ball 2 bbl. that BARELY allows 185 C.F.M. of air intake. When all the math was crunched at Burbank Speed and Machine, the engine needed a minimum of 400 C.F.M. to produce 190 horse power. 500 C.F.M. will allow its' full power of 245 H.P. at the the crank flange. As a result of the smaller carb. the engine is producing only 45% of its' full potential. It runs out of air intake and is most irritating, AND this is why I am curious about the C.F.M. rating of the Stromberg carburetor.

[Dr Deuce]

The "round runners" are the cast tubes from the carb to the head interface. Notice how flat the ones are in your picture.

[Joe Gopan]

Th Intake featured is the OEM manifold for the M-133 Series CMC 6X6, it is flat appearing and not rounded thruout its length. The 3 round holes mate up to the head with 3 Pilot Rings inbetween that seal the head and manifold. These Pilots
are the large diameter for the M-Series GMC .

If you want it to run right, go to MEMPHIS Equipment and buy one of their remanufactured Holley Carburetors made for the M-211. It involves vacuum lines to the Holley Centrivac Governor that is a part of the OEM Carb. Do not try to install the similar Holley from a REO Gasser. It is a 2 Barrel made Just for the M-Series GMC
Only then will this truck run right.

[Joe Gopan]

The 270 GMC Head came in two styles,39-52 with the small Intake Pilots, and after around 1952 the 302 head with large Pilot Rings was installed. Many "DIY" mechanics are not even aware of these differences or are familiar with the early small and later larger Pilot Rings.

[D.R.H.]

Here is what I've found so far about the correct carburetor that Ben is suggesting/recommending. It is a Holley Model 885-FFG, also known as :The Teapot Carburetor. The hole for the intake is for a horizontally mounted air cleaner extension tube. This means more problems with how and where to mount the air cleaner!!
What I can't seem to find is the Cubic Feet per Minute of Air Flow though IT. This is the most important Tid-Bit of information I need. I have found several of the carbs. on Ebay ranging in price from $125.00 to $450.00, all of which have been rebuilt and are ready to go. BUT, if the C.F.M. flow is going to be less than 450, I won't spend a dime.

[Dr Deuce]

I believe that that Stromberg carb was used on the later GMC 305 V6.

The 2 barrel GMC 302 manifolds have a fatal flaw. The heat box under the carbs crack and disintegrate! I have 4 of these engines and 3 of them have the same problem. The 4th I haven't looked at closely. One has cracks that will need to be welded at some point. The crane CCKW w/302 has the carb sitting up on a pedestal. The material above the runners is gone and someone welded plates in there to prevent exhaust leaks. The third one has NO heat box nor car mounting! I have determined that the problem is the exhaust flange. The 3 bolt hard mounting system is the culprit. with the muffler hard mounted to the frame, if the engine torques over or the frame twists, the pipe coming up to the manifold acts as a lever prying on the manifold set. At an auto parts store, you can buy a 1/2 steel donut. The non-rounded part has a lip that fits up into the exhaust manifold. You need to have a "bell" made into the end of the engine pipe to use it for the rounded end. What this does is act like a ball joint. Use stainless steel bolts and Marsten nuts and do not over tighten them. You want to allow movement. For years I had manifold to head gasket problems with just the 270 stock engines with the 3 bolt flange. All went away when I started using this system. The Chevys, both civy and military do not have this problem because they have a 2 bolt/stud mounting system and use an asbestos double sided donut. It acts like a ball joint. The donut eventually fails, but the head to manifold gaskets have no problems. My $.02 from 39 years with CCKWs and 45 years with Chevys from that era.

[D.R.H.]

Dr. D., I found out ALL of your info while I was cutting my teeth on my 1st. Chevy back in 1995. The main reason for the assembly I purchased was to have a spare on the shelf. I had a pair of Fenton Headers on it, but found the GM ex. manifold to flow well, if not better. I had a Weber 32/36 DGV carb. that I just now found out was rated only at 240 CFM flow. The engine ran well but was still under rated for what was needed.
The Stromberg carb. I have WILL NOT be used. I will be using the Rochester 2GC. There is a guy an hour and a half south of me who specializes in them and He can build one to suit my engines requirements. I appreciate the correspondence with You and Ben.

[Joe Gopan]

I have NOS 302 Intakes for the 302 GI M-211.
Check out the Holley 2 Bbl that goes to a 49 Lincoln, it supposedly fts the GI M-211 intake Manifold.

[D.R.H.]

280 Cubic Feet per Minute of Air Flow maximum is what this carburetor will allow. This just proves that if one looks hard enough for an answer, it usually presents its' self in short order.

[Joe Gopan]

Did you have any reference for the Holley the 49 Lincoln used? I have been led to believe it had the same mounting pattern as the M-Series GMC. Same goes for the Holley used on the M-114 APC.

[D.R.H.]

The two are the same style. And as I said, I will not be using anything with less than 400 C.F.M.

[forestry4evr]

Early smaller diameter intake manifolds can be suitably mated (and sealed) to later larger diameter heads on Chevy engines with the use of aftermarket intake manifold adapter rings. By reversing the rings, one can also mate a late manifold to an early head. It looks like the GMC manifolds/heads may be the same. Perhaps this will eliminate one obstacle holding up your quest.