The Ford Barn

quixotix · 07-08-2023, 07:14 PM

I just bought my first Model A. I cleaned out the carburetor and flowed the jets. Even with an idle jet that is large (68 ml/min), the engine was idling lean (around 450 rpm) even with the idle mixture screw all the way in.

After some messing around, I found the intake manifold gasket was leaking at the rear intake port. After disassembly I discovered the manifold gaskets ('31 style - copper with slots for the bolts) were in good shape but sat just a little off center. The holes in the gaskets for the intake ports are significantly larger than the passages in the manifold. With the gasket sitting just a little low (maybe 30 to 50 thousands), the hole in the gasket was right at the outer edge of the intake port of the manifold. This apparently allowed for a small air leak.

Are the intake holes in all the gaskets larger than the intake passages? Or do I need a different gasket?

Note 1: I have a Model B intake manifold on a Model A block if that is significant.

Note 2: By carefully centering the gasket as I installed the manifolds, I think I solved the leak. But I'd feel better if the gasket was not so close to the edge.

Note 3: I did put a straight edge across the manifolds, and all 6 ports seem to be flat and in alignment.

07-08-2023, 07:14 PM	#1
quixotix Junior Member Join Date: Jul 2023 Location: Seattle area Posts: 4	Manifold gasket hole size I just bought my first Model A. I cleaned out the carburetor and flowed the jets. Even with an idle jet that is large (68 ml/min), the engine was idling lean (around 450 rpm) even with the idle mixture screw all the way in. After some messing around, I found the intake manifold gasket was leaking at the rear intake port. After disassembly I discovered the manifold gaskets ('31 style - copper with slots for the bolts) were in good shape but sat just a little off center. The holes in the gaskets for the intake ports are significantly larger than the passages in the manifold. With the gasket sitting just a little low (maybe 30 to 50 thousands), the hole in the gasket was right at the outer edge of the intake port of the manifold. This apparently allowed for a small air leak. Are the intake holes in all the gaskets larger than the intake passages? Or do I need a different gasket? Note 1: I have a Model B intake manifold on a Model A block if that is significant. Note 2: By carefully centering the gasket as I installed the manifolds, I think I solved the leak. But I'd feel better if the gasket was not so close to the edge. Note 3: I did put a straight edge across the manifolds, and all 6 ports seem to be flat and in alignment.