Six Pack Carb Questions

[Iroll65coronet4speed]

Hello Guys,

Please try to keep an open mind with this one. I am not a carburetor guy at all.

I want to post some pictures of some carburetors and need your opinion/help. I build Marine engines and these carburetors fit a 3.0L Chevy (140 cid) marine application. I have adapter plates that I can make and machine to adapt to the original Holley pattern for the six pack intakes. To the best of my knowledge, these are 300 CFM carburetors and you can get different jets (of course). The reason I am going down this road is because I want three carburetors on my 440 stroker (493 cid) and I was going to put these (along with the adapter plates ) because then I could get round air filters and not run the "six pack" air filter assy. I have some pictures attached of what I am looking at.

Do you guys think these would be enough carburetor for the engine? I was originally going to put a 750 or 850 carb on my stroker.

Don't pay any attention to the black cylinders with the plug. They are to help the carburetor start easier and you can replace with regular chokes.

Any help/advice on weather this could be done and maybe what it would take to make it happen would be awesome. If I could get this to work, it would definitely be one of a kind and I would certainly share whatever I learned in the future.

Thanks

 

[Meep-Meep]

Good parts are where you find them, and if you're swimming (bad pun) in marine carbs then that's what you will use. Once again, carbs can be pretty complex but really just rely on a vacuum signal to work properly. Does/will your engine make good vacuum? What cam? What compression? Will you run them all tied together or progressive? Those are 2GC Rochesters I believe and they should have no problem feeding the engine up to 5000 RPM or so plus it's always better to err on the small side for street engines. Also, many people think the factory six pack carbs total 1350 CFM. Well, they don't when you look at them in 4 BBL ratings. And the divided plenum intake sort of fools the engine into thinking it has smaller carbs on it by improving the vacuum signal.

 

[Iroll65coronet4speed]

Meep Meep thank you so much for replying! I am not at all trying to take away from the six pack set up and the cars who have them. As they say.. "Imitation is the greatest compliment". Although I put this out there for you guys to see... I have to admit I was not sure what type of response I was going to get. They can look nice all day but if they don't work then it does not matter. That is why I asked you guys how you thought they would work.

I am going to have a 10.5:1 c/r and Comp has recommended I run a 280/231 with .480 lift. The guy there told me to specify a 114 separation on the lobe as opposed to the normal 110. I have not built the engine yet but what you are saying is that I have to make sure the build is going to have good vacuum? That is advice I am going to take because I told the cam guy that there would not be any need for accessories relying on vacuum and this is the grind he gave me.

These carburetors are actually "MerCarbs" made by MerCruiser (Mercury Marine). This is the carb they use on their 140 horse (181 cid) 4 cylinder Chevy engine. I was going to run them all tied together but what do you think? Holley actually makes a marine 2 barrel carb in 300 and 500 cfm as well that is used on Volvo Penta 4 cylinders (same Chevy 181 cid engine).

I still have a lot to do like check center lines on the intake to see if these will even fit. I hope they would fit under the hood with no problems. These are all thing I can do but the workmanship on the engine was my biggest question because I know nothing about carbs other then you bolt them on and they work and may have to change the jets to make the engine run richer or leaner.

Again I thank you for responding to this post and anymore advice you can give would be great. Believe it or not, Chrysler made marine engines (including the 426 hemi) all the way up until the late 1980's and there are still a lot of them around.

 

[Meep-Meep]

They sure look like they are modeled after the 2GC. What is the throttle bore and main venturi diameter? Anyway, I'm sure you can get them to work with some tuning. The 114 Lobe sep cam will be a good choice for an all around driver because the torque band will be spread out over a wider RPM range. It should also make good vacuum, which will allow your carbs to work pretty well as they are.

I'd try them out as a progressive set up and see how that goes. Run off the center then feed the outers in a little more than half throttle. Or you can hook them up like the Ford Tri Power where the rear carb starts to come in before the front carb.