Which compression for 557ci ???
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Which compression for 557ci ???
Hello, I'm trying to work out what pistons to go with the Scat 4-500 crankshaft and 6-7 Rods, I have been looking at the Keith Black
402 or the 403 pistons, With the 402 pistons they are 20-5cc step dish and the 403 are 30cc, I'm trying to stay under 11-1 so that I can use 98 octane fuel, Camshaft has 649/642 lift, @ 050 270/276, Advertised duration 310/314, Victor intake, 1050 two circuit Dominator and Edelbrock 61649 C/J heads, Can some-one help me work out compression with the above 2 pistons-Bore size will be 060, Thanks.
402 or the 403 pistons, With the 402 pistons they are 20-5cc step dish and the 403 are 30cc, I'm trying to stay under 11-1 so that I can use 98 octane fuel, Camshaft has 649/642 lift, @ 050 270/276, Advertised duration 310/314, Victor intake, 1050 two circuit Dominator and Edelbrock 61649 C/J heads, Can some-one help me work out compression with the above 2 pistons-Bore size will be 060, Thanks.
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Thanks, I just changed camshaft- I went with a Lunati solid camshaft from car shop inc ( Thanks Tim ) Lift is 610/625 , duration at 050 272/279, advertised duration 314/320. Its a little less lift that the comp cams but with more duration. I am only going 060 over in bore size darrin1999 so will compression be the same- 10.87 ? Thanks Jamie.
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From: iowa
it's close Jamie, on a 4.420 bore (.060 overbore) with the 75cc chamber for that head and all the rest it works out to 10.81
But something to check, the KB-403 pistons list as 6.7 rod with a 4.3" stroke. make sure of your pistons before ordering.
But something to check, the KB-403 pistons list as 6.7 rod with a 4.3" stroke. make sure of your pistons before ordering.
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Checked the KB web site.... they have kb860 forged pistons 22cc dish that will give 11-4-1 with the 61649 C/J 75 cc chambers, Is 11-4-1 compression to high to use 98 octane fuel ??? As I will have to change order asap, Thanks.
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From: fargo, nd
youre from australia right? that 98 octane is the equivalent to our 93/94 octane... but with 0 decking the block and using a thin head gasket your quench will be set up properly to reduce detonation, and with a cam that size i think youll be able to get away with 11.5-1 but youll have to have the tune right on.
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youre from australia right? that 98 octane is the equivalent to our 93/94 octane... but with 0 decking the block and using a thin head gasket your quench will be set up properly to reduce detonation, and with a cam that size i think youll be able to get away with 11.5-1 but youll have to have the tune right on.
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From: fargo, nd
as long as your quench distance (distance from the top of the piston to the bottom of the head) is under .050 youre ok... but the tighter you get it the better off you are. usually .030-.045 is whats recommended, so standard .041 will be ok with a 0 deck block. factory the piston is usually around .030 down which totally screws quench.
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From: iowa
you have the advantage of the alum head also. polish the combustion chamber smooth, and as Darrin said zero deck the block (or no more then .010 in the hole will work too) and you should be good to go. Your cam is big enough to scrub some of the compression.
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Thanks, One last Question !!!! Some-one has said the Scat 4-500 crankshaft is Internally Balanced.... I Told Him its EXTERNALLY balanced and that i still use the weighted crank spacer-at front of crankshaft and my Externally balanced flywheel- Am I right ??? And the powerbond damper is neutral balance, Im pretty sure I am spot on, Thanks for all the help & info, Jamie - Australia.
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