Tech / General EngineIs your car making a strange sound or won't start? Thinking of adding power with a new combination? Need other technical information or engine specific advice? Don't see another board for your problem? Post it here!
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I just recently put 081 TPI heads on my TBI 305 with a ZZ4 cam. I have to pull the heads again because I didn't get screw-ins and its pulling the studs. So, the heads had been cleaned rebuilt and resurfaced. Nothing was done to the block though.
I'm wondering, can I go with a thinner gasket to up compression a little, maybe squeeze out a little more from this motor. Or should I not use anything thinner than stock without knowing for sure the block is FLAT. Block has about 75k miles on it. It's in very good shape, but I'm not sure which gaskets I'm safe to go with. Any advice is appreciated, thanks.
Lay a machined straight edge bar across a CLEAN block deck surface (top, middle, bottom and corner-to-corner in both directions) and try to shove a .004" feeler gague under it at various points along it's length. If it slides under at any point the block is beyond GM spec for flatness. For a performance application or for thin steel shim type head gaskets it's best if it's less than .002"
Thanks, I'll do that when I pull them and clean it up. Any specific gaskets recommended. Last I went with just standard replacement Fel Pro ones. Not sure on the compressed thickness, but I was shooting for something thinner this time if I could get away with it.
FP-1003 has a high volume 9.158. A better boost in compression could be had from using the FPP-1094 it's volume is 3.245 compressed. On my engine that would equate to a change from 9.33:1 to 9.94:1
Here are some more:
Part# - Bore - Comp Thickness - Volume
I too recommend the FP1094 gasket. It is thin and coated, along with having a smaller bore then many others. This is important on a 305, and more so as the gasket thickness increases. Can produce a large dead-zone.
Alright, thanks a lot guys, I'll probably check the block and go with the 1094 then if it's straight.
I'm figuring that it's impossible to get optimal quench on a motor that has not been zero decked and is still stock. Correct? Isn't optimum around .041.
Originally posted by RBob I too recommend the FP1094 gasket. It is thin and coated, along with having a smaller bore then many others. This is important on a 305, and more so as the gasket thickness increases. Can produce a large dead-zone.
Handy chart Zed'er.
RBob.
Thanks. I just copied and pasted from an excel spread sheet I made for calculating engine compression ratios. I keep a database of gaskets, pistons, heads, blah, blah, to keep me from having to search all the time...
