[jonathonar89]

Got an oddball question here. I just bought a 80-81 NA 301 manifold to try and do an EFI install on my ‘79 400.

Has anyone ever tried milling off the ball/socket to convert to a flat gasket on a log manifold? I’m figuring I can do this so that I can open up the diameter of the inlet/outlet to run a slightly larger crossover and down pipe (hopefully 2.5 crossover and downpipe).

Also, any recommendations to filling in the center hole which is not needed for the earlier style d-port head? Tap it and mill a bolt flat on the back side? What could I use for a filler material if that’s possible?

[242177P]

Get an earlier manifold, and simply weld a sensor bung into your headpipe instead.

[jonathonar89]

Originally Posted by 242177P

Get an earlier manifold, and simply weld a sensor bung into your headpipe instead.

My car is in project mode. I'm going to try and make this work. I'm going for a factory appearing install and low cost. Performance is a thought but not as much of a priority.


Untitled by Jonathon Randolph, on Flickr

[Schurkey]

Originally Posted by jonathonar89

I'm going for a factory appearing install and low cost. Performance is a thought but not as much of a priority.

Why bother to spend all the extra money for fuel injection if performance is an afterthought? A properly set-up carb will give you everything that FI gives you, and potentially better fuel economy as a bonus.

[jonathonar89]

Originally Posted by Schurkey

Why bother to spend all the extra money for fuel injection if performance is an afterthought? A properly set-up carb will give you everything that FI gives you, and potentially better fuel economy as a bonus.

I have nothing against carburetors. Just doing a fun and different project using factory GM parts and aftermarket computer. The TBI I have is a Rochester (same people who made the quadrajet).

454 TBI was $30-$40.....o2 301 manifold $75....Innovate Motorsports wideband $120...Megasquirt 2 efi computer $210...harness $65...’81 301 Pontiac computer distributor $80.

By going used or 2nd-hand-new, I don’t have too much money in it. I’m also working with my engine that was stolen. All the stuff purchased was missing after I got it back.

[b-man]

I think you’re going to have difficulty sealing a flat gasket, the factory went to the tapered seal with no gasket in 1964 probably for that reason.

I’d open them up to accept a 2-1/4” pipe and forget the flat gasket.

[jonathonar89]

Originally Posted by b-man

I think you’re going to have difficulty sealing a flat gasket, the factory went to the tapered seal with no gasket in 1964 probably for that reason.

I’d open them up to accept a 2-1/4” pipe and forget the flat gasket.

You may be right. I went out to the garage just now. Looks like the crossover opening is right about 1.7" and the outlet about 1.9". Both have a flat portion that can open up about .25". Without cutting into the ball portion, it basically can be opened up to a 2" crossover and 2.5" outlet for the downpipe.

Crossover inside diameter....
Untitled by Jonathon Randolph, on Flickr

Outlet inside diameter....
Untitled by Jonathon Randolph, on Flickr

Outlet diameter of flat portion...
Untitled by Jonathon Randolph, on Flickr