Inliners International Forums General Discussion Engines Why not ?

I'm looking at my stock 250 intake manifold and wondering ,,Why can't I have the top(mounting surface ) milled flat and opened up, then mount a 1"spacer/square flange carb adaptor by using countersunk screws threaded into the stock manifold. It almost looks too easy not to do.This would leave the normal area on the manifold bottom for carburetor heat as well. has anyone here ever done it or attempted it?
Any comments or suggestions ?

I have seen a few (very few) at swap meets now and then. How well they worked, That i don't know.
But a small 2b should work fine that way.Or a weber style Like Tom Langdon sells.

This is a common modification to the ford small inline sixes.

Nortin
Yes this can be done but you will discover that there are internal heat passages that you can machine out to gain a larger area. Then you can braze the bottom holes shut to seal up the intake. After that is done you can use a die grinder to smooth the entrance to the intake runners to allow a better flow. If you are using this intake with a stock exhaust manifold you won't need additional heat. If running headers make your alum. plate 1 1/2" thick and larger than needed just to cover bottom of carb, now drill passages through it on all four sides that connect, then tap the holes for pipe fittings. Install hose bibs for your heater hoses then brass plugs to close remaining holes. You will also need to taper the alum plates internal opening to allow a smooth flow from carb to intake. Make the opening at top large enough to clear the carb throttle plates. We used to build a lot of these before four barrel intakes became easily accessible. If you have the skill and the tools it is a very neat project. You can not plug the holes from the heat passsges with epoxy as the exhaust heat will cause it to fail.
Some guys have drilled holes in the alum plate at an angle to match the carb bores to the intake others just make one large opening that tapers to manifold then they can use another plate drilled with holes to match carb to allow a better vacuum signal at low speed. This is a matter of what you desire or believe. I have also seen guys make this alum plate as much as six inches tall going for the ram effect. If you make this up then you can make up dozens of combinations to see what performs best in your application.

Nortin
after reading my above post I noticed that I forgot one impotant step You have to leave ears inside the center opening to bolt the alum plate to the cast intake then cut these down to about 1/2" tall and use 3/8 cap screws to fasten to intake,USE LOCKTITE AND SHAKE PROOF WASHERS ON THESE. some guys fill allen head holes with rtv some don't. I never did because I was afraid it would come loose and suck down into engine. You will also have to make your own gasket to fit between the cast intake and the adapter plate.

A store bought adapter plate wont work because it lacks the ear for bolting it down and I believe the opening is shaped wrong to cover manifold opening you will wind up with.
Good Luck and have FUN