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343 questions

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myrambler View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote myrambler Quote  Post ReplyReply Direct Link To This Post Topic: 343 questions
    Posted: Feb/18/2018 at 8:18pm
I have a 343 engine with aftermarket parts. So far I've been able to identify the following information. The pistons are forged 360 pistons TRW 2358 bored .30 over standard.(Same as 1858P) It has a standard crank, comp 292 cam, aftermarket springs, 1.6 roller rockers. I was told this was in a high revving mud bogger. 
I was sent info from a supplier that claims the pistons have the following spec.
 .190 recess, 1.6 compression distance, 5/64, 5/64, 3/16 ring lands. 
Trying to determine compression ratio and how to proceed on refresh of the engine. I bought a piece of plexiglass and a cc syringe to check cc's of the piston recess and also checked one piston at TDC to see total cc's. The cc's of the piston recess was close to 28, total cc's of cylinder at TDC was 38. I don't know if the block was decked so that is why I checked volume. I don't have machinists tools to accurately measure everything so I'm hopeful someone who knows can assist in determining the compression ratio based on the cc's provided. the heads are the 67-69 343/390 square port heads. 
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WesternRed View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote WesternRed Quote  Post ReplyReply Direct Link To This Post Posted: Feb/18/2018 at 9:06pm
Piston would normally be 0.060”-0.080” down the bore at TDC on a 343 and you would have pretty low compression running dished 360 pistons unless as you say the block has been decked or there are other changes.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote WesternRed Quote  Post ReplyReply Direct Link To This Post Posted: Feb/18/2018 at 9:20pm
I come up with around 8.2:1, with a few assumptions, based on the ratio of your CC values, I've come up with roughly 0.050" deck clearance and I've allowed 0.040" overbore. Head gasket bore may be a bit off, that's just the number that comes to mind for these.

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