compression?

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93toyota

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I got a 360 bored to a 365 which I think is 40 over, stock 78cc heads and kb107 pistons and cant figure out the CR to save my life can anyone help out? oh yea the gasket is either 30 or 40 so maybe you can give me both compressions with the gaskets
 
bitchin' thanks to both
happy thanksgiving
and I thought I was the only sorry fool this obsessed
 
No, your not alone. Myself, heads bike mopars, dgc333, moper and a host of others are mopar crazed and go an extra bit to know what the heck is going on with our engines.
Theres a few shop owners/machinests here as well that are very up on stuff and offer help and share what they know.
All free of charge. Now how cool is that?!?!?
 
most stock SB heads were in the 70-72cc range so 78cc will make quit a difference in your calculations - and final outcome, just a thought
 
Well said Rumblefish. We don't always agree on this board, but everyone is respecful and curtious of each other. Like a ..'family'. A Mopar Family. And yes, some very sharp people here. I know I learn alot from it. Keeps me coming back. And If I don't know the answer, there's always someone here who does. Sure would like to meet some of you guys. I go to the Nats. every year...maybe next year we can all hook up in Columbus. That would be great. Terry.
 
yea that would be cool. By the way the 360 I got is a 91 block that came out of a truck and I believe are 308 heads. When I rebuilt it the machinist and I traced the part #'s on the heads and that is what it was, 78cc. I gotta take his word I guess
 
That doesn't sound right. Perhaps 68 cc's?
 
Well I recommend you have the machinist re-check. I've measured at least 5 sets of LA type heads in the last 2 yrs - 915s, 576, 596, 587 and stock were all in the 70-72cc range, and the 308s measured 72ccs as well. If you went with 78ccs for your calcs and they turned out to be 6cc less it would raise you compression ± 0.6. Up to you.
 
It's easy to actually measure the cc's of your heads. Get a piece of plexi glass that is big enough to cover the chamber. Rill a small hole (~1/8") in it so it will be near the edge of the chamber. Go to the local pharmacy and get a plastic syringe that is graduated in cc's (one that has a ~100cc capacity will be the best).

With the valves installed and a spark plug installed put some greas on the edge of the plexi glass to act as a seal. Using the syringe fill up the chamber keeping track of the amount you put in. You know know the cc's of you heads. Check both ends of the head and take an average.

Also, with you KB107 pistons how far down in the cylinder are they? That will impact your compression too. All the numbers you see advertised for KB pistons assumes you have had the deck on the block machined so the piston is even with the deck (i.e., "zero decked").
 
Yup..like dgc..only way to know for sure, is measure and calculate..I dont think the heads are 78cc either..more like 72+ or - 2ccs depending. The pistons are decent, but the block's deck height (if not corrected) is taller than the blueprint, so the pstons end up lower in the bore than the spec.
 
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