Figuring Compression not what they should be
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From: OK
Car: TBI CHEVY, TPI 5.0 HO
Engine: 5.7 FIRST hp SMALL BLOCK, BIG BLOCKS!
Transmission: 4L60E
Figuring Compression not what they should be
I have a 350, Bored 40, H345NP40 HYP Federal Mogue Pistons, SR Pro Topline (have 2.02-1.60s but not using them no valves etc) heads are 76 cc with .020 shaved off heads and thinner gasket, .015 Fel Pro 1094) for better quench, 40 vs 60+, 1.94-1.50 Valves, Cam 212-215 @50, 444 Lift with out allowing for 1.6 Comp Cam.
What do you need to figure Actuale compression
What do you need to figure Actuale compression
Last edited by 1993GMCPU; Jun 13, 2004 at 02:06 AM.
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Thread Starter
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Joined: Jan 2004
Posts: 112
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From: OK
Car: TBI CHEVY, TPI 5.0 HO
Engine: 5.7 FIRST hp SMALL BLOCK, BIG BLOCKS!
Transmission: 4L60E
How do I get other things like cylinder displacement etc:
Specifications:
* Bore: 4.040 in.
* Stroke: 3.480 in.
* Rod length: 5.700 in.
* Compression ratio: 10.01:1 (58cc heads), 9.39:1 (64cc heads), 9.02:1 (68cc heads), 8.68:1 (72cc heads), 8.37:1 (76cc heads),
* Head type: Flattop with 4 valve reliefs
* Oversize: .040 in.
* Ring size: 5/64 in. top ring, 5/64 in. second ring, 3/16 in. oil control ring
* Weight: 595 grams
It's cylinder displacement + piston dish (or - for domes) + gasket volume + piston deck height volume + combustion chamber volume
divided by.....
piston dish (or - for domes) + gasket volume + piston deck height volume + combustion chamber volume.
Specifications:
* Bore: 4.040 in.
* Stroke: 3.480 in.
* Rod length: 5.700 in.
* Compression ratio: 10.01:1 (58cc heads), 9.39:1 (64cc heads), 9.02:1 (68cc heads), 8.68:1 (72cc heads), 8.37:1 (76cc heads),
* Head type: Flattop with 4 valve reliefs
* Oversize: .040 in.
* Ring size: 5/64 in. top ring, 5/64 in. second ring, 3/16 in. oil control ring
* Weight: 595 grams
It's cylinder displacement + piston dish (or - for domes) + gasket volume + piston deck height volume + combustion chamber volume
divided by.....
piston dish (or - for domes) + gasket volume + piston deck height volume + combustion chamber volume.
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Re: Figuring Compression not what they should be
Originally posted by 1993GMCPU
I have a 350, Bored 40, H345NP40 HYP Federal Mogue Pistons, SR Pro Topline (have 2.02-1.60s but not using them no valves etc) heads are 76 cc with .020 shaved off heads and thinner gasket, .015 Fel Pro 1094) for better quench, 40 vs 60+, 1.94-1.50 Valves, Cam 212-215 @50, 444 Lift with out allowing for 1.6 Comp Cam.
What do you need to figure Actuale compression
I have a 350, Bored 40, H345NP40 HYP Federal Mogue Pistons, SR Pro Topline (have 2.02-1.60s but not using them no valves etc) heads are 76 cc with .020 shaved off heads and thinner gasket, .015 Fel Pro 1094) for better quench, 40 vs 60+, 1.94-1.50 Valves, Cam 212-215 @50, 444 Lift with out allowing for 1.6 Comp Cam.
What do you need to figure Actuale compression
You need to measure the piston deck clearance at TDC on your assembled motor. Also not hard to do.
the nominal deck clearance for those pistons in a non decked stock block is .045". Yours may be more or less.
.055" below deck at TDC is not unusual.
The volume of the piston valve reliefs is 5cc's.
The volume of a .015" thick shim type gasket is 3.5cc.
the gasket bore size is 4.10", the thickness is .015"
you can GO HERE
and find the engine cr calc and punch in the numbers to find your cr.
Going to be just over 9:1.
Last edited by F-BIRD'88; Jun 13, 2004 at 03:08 PM.
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From: OK
Car: TBI CHEVY, TPI 5.0 HO
Engine: 5.7 FIRST hp SMALL BLOCK, BIG BLOCKS!
Transmission: 4L60E
I appreciate that a lot, thanks, so it's in area we wanted which is above 9.0, except not sure what SR is yet.
40 over motor should be ok and smaller valves I had hoped would match smaller Factory style TBI we are going back to all factory except cam even though I like 212 LSA I seen and if I get better like to try one of Summits. Present cam has a 212-218 Duration 444 Lift cam sort of short on lift?
Well 1.6 Rollers helped as I was hoping to get around 266-224 @ 50 durations and only wished I gotten more lift on exh. Hope motor runs and no more setting around!
:lala:
40 over motor should be ok and smaller valves I had hoped would match smaller Factory style TBI we are going back to all factory except cam even though I like 212 LSA I seen and if I get better like to try one of Summits. Present cam has a 212-218 Duration 444 Lift cam sort of short on lift?
Well 1.6 Rollers helped as I was hoping to get around 266-224 @ 50 durations and only wished I gotten more lift on exh. Hope motor runs and no more setting around!
:lala:
Last edited by 1993GMCPU; Jun 13, 2004 at 11:16 PM.
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