I have a 340 with kb 243 pistons and i am using rhs heads 1.92 intake. My question is the kb website has 64 cc heads at 9.4-1 and mancini has the 243 pistons at 9.5-1 with 72 cc heads. SO what compression would I really have with 62 cc heads? I have holley 3310 edelbrock airgap. So would the comp 507/510 be good for this build?
340 build ?
- Thread starter dart76
- Start date
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This can not be right on the compression of these pistons. Can anyone shed some light on this?
http://www.kb-silvolite.com/kb_car/performance.php?action=details&P_id=135
http://www.kb-silvolite.com/kb_car/performance.php?action=details&P_id=135
what is deck height is your pistons...what head gasket are you going to use...
those effect your compression ratio....
you are only guessing if you dont know them....plus rhs heads are close chamber heads and kb243 pistons should have a positive deck height....
those effect your compression ratio....
you are only guessing if you dont know them....plus rhs heads are close chamber heads and kb243 pistons should have a positive deck height....
Actually, if you look at the KB website, they list a 64cc chamber at 10:1. A 62 cc chamber will give you around 10.2:1 with a .040" thick head gasket. As far as the mancini site goes, I don't know why the header says 9.5:1, the description says 10.2:1.
Be advised though, that you're going to want to check your piston to head clearance. The KB 243 should be .018" above the deck at the top of the piston, and that may interfere with a closed chamber head (like the RHS). You should definitely check your piston to head and your valve to piston clearance before you run the 243's with a closed chamber head. This is why Edelbrock makes an open chamber head for the 340's and a closed chamber head for the 360's.
I just bolted a set of 308's (open chamber heads) onto my 340, which has 243's. I have a 64.5 cc chamber, and after talking directly with KB about my engine and its specific measurements I should have a 9.9:1 compression ratio, but I'm at .060" over on the pistons.
Be advised though, that you're going to want to check your piston to head clearance. The KB 243 should be .018" above the deck at the top of the piston, and that may interfere with a closed chamber head (like the RHS). You should definitely check your piston to head and your valve to piston clearance before you run the 243's with a closed chamber head. This is why Edelbrock makes an open chamber head for the 340's and a closed chamber head for the 360's.
I just bolted a set of 308's (open chamber heads) onto my 340, which has 243's. I have a 64.5 cc chamber, and after talking directly with KB about my engine and its specific measurements I should have a 9.9:1 compression ratio, but I'm at .060" over on the pistons.
The KB site sez;
Compression Ratios
57-10.9
60-10.5
64-10.0
68-9.4
and I entered 72 cc for 308/J etc... heads. It came to; Compression Ratios 9.158 - 1.
What you and we really need to know is the gasket dimentions, bore and thickness and the head cc amount. The piston dimentions as well and how far above the deck it sits.
All of these dimentions needed to be inputed into a calc.
Compression Ratios
57-10.9
60-10.5
64-10.0
68-9.4
and I entered 72 cc for 308/J etc... heads. It came to; Compression Ratios 9.158 - 1.
What you and we really need to know is the gasket dimentions, bore and thickness and the head cc amount. The piston dimentions as well and how far above the deck it sits.
All of these dimentions needed to be inputed into a calc.
lead69
hopeless car junkie
If the block hasnt been decked you may wind up at zero deck,most 340s do stock,if you do you can use any gasket with .040 or more roughly.If you are above deck you can use some cometics to get the correct quench,you will need the proper finish on both the deck and block to run them and they are more money.
thanks I had the heads and then this short block came up so im trying to make it work.
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