Bgdaddy455

Can anyone recommend the gasket that goes between the head and intake? What I mean is i heard there are different sizes for different applications so i want the to be able to have the best flow possible for a 455 with C heads, compression will be 10.5:1. I do have headers but not sure if that is relivent at this point. Thanks for any input.

Schurkey

Gasket matching at the manifold/head area is nearly pointless. The pushrod pinch, and the bowl/short turn is where EFFECTIVE porting happens.

Use whatever size gasket has port openings that match your cylinder heads and intake manifold.

I made a mistake on a SBC, used a "hot-rod" gasket that was one size too large for the manifold and head ports. Gasket squeezed out, created a vacuum leak. Two dead cylinders (#1 and #3) at idle. Other cylinder pairs were almost to the point of leaking.

grannys442

ditto ^^^. Intake-to-head port matching was shown to make little or no positive improvement during an exhaustive intake manifold dyno comparison on Ford FE engines. I’m not saying there’s no configuration that would benefit, but suspect it would only be beneficial on extreme high end/RPM build

Bgdaddy455

Thats the kind of info that helps. So just a stock gasket most likely

joe_padavano

There's another thing to consider when port matching. What ensures that after you go through all this trouble, the ports in the intake actually line up with the ports in the heads? The answer is, nothing. The intake bolt holes are clearance holes with a fair amout of slop. The location of the intake on the heads is governed by the location of the gasket surfaces relative to the block. Any milling of the heads, decking of the block, differences in compressed head gasket thickness, or milling of the intake will change that relationship, which pretty much negates any port matching. I remember an article in Car Craft decades ago where they showed you how to use a bent coat hanger to probe down into the intake ports and check for alignment mismatch between the intake and heads. That only works on a single plane intake with relatively straight runners, unfortunately. A borescope inspection camera might be the clever way to do that today.

Bgdaddy455

Thanks for the input. I like the bore scope idea. May be the only way to see what is actually happening.

Schurkey

I was told to fit the manifold to the engine using all the same dimensions the finished engine would use--deck height, head gasket thickness, head-planing done, intake manifold planing to match. (i.e., the intake manifold fits perfectly.) Then the intake face of the head, the intake gasket, and the intake manifold is drilled for a pair of dowel pins on each side. With the alignment of the parts assured, then the gasket-matching begins. Any further machining of the engine parts would need to have gasket thicknesses adjusted accordingly.

And, all of this would be done as part of a FULL PORTING, not just a simple "gasket match" which, as I said, is worthless without the rest of the port and valve-seat work.

Keep in mind that guys used to put big-block Chevy rectangular-port intake manifolds onto oval-port heads, and claim an improvement in power based on the availability of "high performance" rectangular-port manifolds. Port matching would be a complete disaster in this instance...and yet it seemed to work-out OK.

joe_padavano

^^^THIS. That is about the only way to guarantee alignment and location repeatability.

Jeff Stout

Have not worked on my 455 yet but the 307 intake had smaller runner then the head. For Stock eliminator I cant open them but it is a large amount of mismatch. Opening the intake to match head would help a lot.

Bgdaddy455

I didnt realize they had all the different gaskets at different thicknesses. So with all the other porting done correctly it is worth gasket matching to increase flow. Thanks.