The Ford Barn

wearymicrobe · 10-04-2013, 04:01 PM

Quick question I have a 312 y Block that has ~1500 miles on a rebuild. Only problem was it was rebuilt built in ~1983.

I have been going through the motor and it runs just fine with a rebuilt carb and a F100 distributor with the proper vacuum advance.

Only issue is at idles at ~600rpm the motor shakes a good bit more then I remember. Engine mounts are fresh and anything above idle it smooths out immediately. Plug are the proper color and the car does not hesitate off idle.

Manifold vacuum is very very low though, ~11in/mg, it jumps right up to where it is supposed to though at anything above ~800rpm. Compression is clean as well.

Sounds like a intake gasket right? Anything else that I should do while I have the manifold off the motor. Its a major pain to remove and I do not want to do it twice. Carb gaskets are already new and of good quality.

Also is there a preferred manufacturer for the 312. I have had a few gaskets in the past be to think to get to seat properly.

Anything else to look for.

10-04-2013, 04:01 PM	#1
wearymicrobe Member Join Date: Feb 2011 Posts: 31	Rough Idle on 312, Intake Gasket failure. Quick question I have a 312 y Block that has ~1500 miles on a rebuild. Only problem was it was rebuilt built in ~1983. I have been going through the motor and it runs just fine with a rebuilt carb and a F100 distributor with the proper vacuum advance. Only issue is at idles at ~600rpm the motor shakes a good bit more then I remember. Engine mounts are fresh and anything above idle it smooths out immediately. Plug are the proper color and the car does not hesitate off idle. Manifold vacuum is very very low though, ~11in/mg, it jumps right up to where it is supposed to though at anything above ~800rpm. Compression is clean as well. Sounds like a intake gasket right? Anything else that I should do while I have the manifold off the motor. Its a major pain to remove and I do not want to do it twice. Carb gaskets are already new and of good quality. Also is there a preferred manufacturer for the 312. I have had a few gaskets in the past be to think to get to seat properly. Anything else to look for.