Originally Posted by Bersaglieri

Ok, if you plan on adding some gear later, something of the CC306 size would like it. 3.42 is a good street gear, but if it's more of a toy you can get away with 3.73 and 4.10 pretty easily.

The .039" gasket is your problem with compression. It's also going to hurt your quench which should be a little tighter than .054"; moving it down to .041"quench with a .026" gasket will bump the compression and combat detonation.

Assuming a 56cc head, 5cc piston, 4.100 gasket bore, .026 gasket, .015 piston depth, 3.48 stroke, and 4.030 bore that'll put you at 11.43:1 static. Have Lloyd move the head cc around if needed to add or deduct the static compression if necessary. a 54cc would make it 11.74, a 58cc 11.14. A CC306 will want more compression, but a well thought out camshaft can do more with less. These are some of the details that make or break a build. Guys who just throw crap together typically wind up with mediocre results.

If you can spring for heads, I'd do it, it'll save you lots of hassle later, added labor, new gaskets, new fluids, time, new tune, etc. It's worth spending a little more do it right the first time.

If your stuck with an shelf cam look into Lunati grinds, those are the best off shelf grinds for LT1's in my opinion. The Voodoo line is very nice, a 231/239 60122 would be a great street machine cam for a hot 355 with gears. But for a tiny bit more, Lloyd can tailor something to your exact needs and match it up to the heads.

Originally Posted by hulettsz28

Use the 306. Alternatively, how about returning the 503 and 306, getting a package from Lloyd Elliott, and saving yourself the trouble of tearing it apart twice?