First motor start, terrible knocking

[Marshy]

Originally Posted by Lefkada

I'm having trouble figuring out the head gasket thickness. I used the heads gaskets from this Fel-Pro KS2600 kit: https://www.summitracing.com/parts/fel-ks2600/overview/

Those have the fel-pro 7733PT-2 gasket and is .039-.040" compressed.

Let us know the cylinder head casting #'s when you get a chance.

Last week there was a guy asking if he could bolt on a pair of Vortec heads and replace a set of 882 heads. I told he he could but needed to consider the change in compression because the vortec heads were 64cc's vs the larger 74cc's of the 882 heads. I gave an example with flat top pistons with -4cc valve reliefs and a .040" quench clearance the compression was 9.5:1 with the larger heads but jumped to something like 10.5:1 (IIRC) by bolting on the smaller heads. The example I chose sounds like it could resemble your build but obviously just a guess because you don't know your deck height. It wouldn't be uncommon to zero deck a block and run flat top pistons and that head gasket like you have. Just something to be aware of.