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Intake manifold

missnancy

missnancy

Regular Contributor
I have an intake manifold on my 350 which was originaly off a 283. The reason I am using it is due to the fact that instead of a single gooseneck for the cooling hase I have two of them. One on each side of the intake. The coolent reservior mounts where the gooseneck would have been. The problem I have is the only carb I can use is a rochester 4 jet which has the same size main and secondarys. The manifold is drilled to accept ithe 4 jet. I can bolt on a spread bore carb but the secondarys will not open as the holes are to small.

That said, can I take the manifold to a machine shop and have them bore out the secondary holes without a problem or will I cause a whole new set of problems. I cant use an adapter plate due to clearance in the engine space. Thanks in advance for the help guys.
 
As you suspected, the adapter plate will not "enlarge" the holes in your old manifold. Frankly, unless you run wide open all the time, you don't need more carburation. My boat, for example, only sees the four barrels on my annual test ride.

Jeff
 
MissNancy: sounds like you have an old 4G rochester - doesn't it have like 4 (maybe 6) vent stacks around the air horn opening? If it does, then I doubt you can bolt a spreadbore (quadrajet) carb in its place unless the manifold has been modified.

A competent machinist should be able to give you a GO or NOGO on your proposed mod, if you take him all the parts.

Personally, I'd be inclined to swap the manifold and carb for something more 'modern' that can be rebuilt when needed. I'm thinking modifying the cooling system may be cheaper in the long run.

That said, Exactly what is the issue that spawned the question on the intake?
 
The only Rochester carb I ever worked with was a 2 bbl adapted for use on my 1974 FJ-40 Land Cruiser by Man-A-Fre, a California based 4x4 place..37 yrs ago. I can honestly say that FROM WHAT I READ...the Rochester carb can be difficult to set up properly...AGAIN...NO EXPERIENCE only from WHAT I READ HERE.

Our set up with the Edelbrock has been a tinkerers dream. It is so easy to work on, rebuild and modify(if necessary). Depending on what you are looking to spend, Paul, I can easily represent the plus sides to this carb as a positive experience. They will be going on 5 years old, I have rebuilt them once when we first acquired the boat so that we knew what we were dealing with from square one. IF you are looking for a recommendation...here's one...BTW: We are using adapters to the 454 manifold
 
Makomark, Yes, it is the 4g or 4jet carb depending on who is describing it. What brought the question up is the age and availibility of parts for the carb. The cooling system and the way it is run is why I don't want to change the manifold if there is another option. The main problem with the manifold is that there are two goosenecks in the manifold I have and each one goes over to the exhaust manifold on each side. If there was a single goose neck that split into two like a y then that would allow me to change manifolds I think. Mainly I am just spit balling here.

Jeff, my avarage cruise rpm is around 3200 rpm and with the 4g I am only able to get her up to around 3800 at the top. With a 350 I shoud be able to get her to turn up more then that.

Knuckle47, I have a problem with the highth of the carb so I think that the adapter plate would raise the carb up to high and the engine box cover would not sit right.

Thanks guys, I think it will be a case of more reseach.
 
That's not a lot of WOT rpms, but if the bot isn't laboring to plane off--and holds plane well--then I'd leave it alone.

Jeff
 
The carb parts have been NLA for decades for the 4G's.....I'd call Cliff and see if he has any "replacement ideas". He may have run across this same issue during his track racing activities. 740.397.2921
 
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