Help on dynamic compression!
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Help on dynamic compression! I have a block at the machine shop now getting bored .040 over 3.750 forged crank and 6" forged rods to make a 385. The Pistons have a -5 valve relief. So it should put the static compression 11.4 to 1 with 62cc heads.
I was going to go with the lunati 60122 cam, but with the intake closing at 41.5 abcd. It would put the DC over 10?
The cam is measured with 1.5 rockers and I am going to be using 1.6 rockers.
Am I adding it up or looking at the wrong calculations or do I need a different cam?
I was going to go with the lunati 60122 cam, but with the intake closing at 41.5 abcd. It would put the DC over 10?
The cam is measured with 1.5 rockers and I am going to be using 1.6 rockers.
Am I adding it up or looking at the wrong calculations or do I need a different cam?
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http://www.wallaceracing.com/dynamic-cr.php
Type your setup in the calculator and see what your dynamic compression is. Need to look at your cam card and see where the intake valve closes abdc.
Mine closes at 41.5 but I wanna make sure I am running all the numbers right.
Type your setup in the calculator and see what your dynamic compression is. Need to look at your cam card and see where the intake valve closes abdc.
Mine closes at 41.5 but I wanna make sure I am running all the numbers right.
Use the .006 tappet lift duration numbers for those DCR calculators.
IVC is 67 deg ABDC for that cam.
It your SCR is 11.4, I get 8.95 DCR using the Pat Kelley calculator.
You're good!
IVC is 67 deg ABDC for that cam.
It your SCR is 11.4, I get 8.95 DCR using the Pat Kelley calculator.
You're good!
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http://www.wallaceracing.com/dynamic-cr.php
Type your setup in the calculator and see what your dynamic compression is. Need to look at your cam card and see where the intake valve closes abdc.
Mine closes at 41.5 but I wanna make sure I am running all the numbers right.
Type your setup in the calculator and see what your dynamic compression is. Need to look at your cam card and see where the intake valve closes abdc.
Mine closes at 41.5 but I wanna make sure I am running all the numbers right.
Using your info, I get the same result as BowtieNut.
Last edited by hrcslam; Jun 14, 2016 at 06:09 AM.
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OP, what specs are you using to get 11.4:1 SCR? If I assume a stock deck height (0.025"), with a .035" head gasket (4.120" bore for the head gasket), and a large 58cc head CC (Stock LT1 specs say 54cc, but actual varies a bit), I get 11.37:1. But, that gives you .060" quench. I'd be worried about that quench. My quench is .043" (which is a little too big for my liking).
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He said 62cc heads. I used a typical 4.100" bore gasket, .026" thickness, and adjusted deck clearance to .014" (0.040" quench) to get his stated 11.4:1 SCR. That cam is 282/290 advertised, 110 LSA, 106 ICL.
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Teching In
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OP, what specs are you using to get 11.4:1 SCR? If I assume a stock deck height (0.025"), with a .035" head gasket (4.120" bore for the head gasket), and a large 58cc head CC (Stock LT1 specs say 54cc, but actual varies a bit), I get 11.37:1. But, that gives you .060" quench. I'd be worried about that quench. My quench is .043" (which is a little too big for my liking).
I have the block zero decked bored .040 over with a .040 head gasket. Pistons -5 valve relief with 62cc afr heads 6" rods with a 3.750 crank. All forged with Ross 2618 alloy Pistons. Going to be spraying 200-250 shot through a nitrous outlet plate.
No.
Yes!
Or....you can go as tight as 4.060" if you're feeling REALLY frisky.....but I'd only use that, or the 4.040" gasket, for a stock cylinder bore (4.00").
KW
Yes!
Or....you can go as tight as 4.060" if you're feeling REALLY frisky.....but I'd only use that, or the 4.040" gasket, for a stock cylinder bore (4.00").
KW
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So with the motor being 40 over, C5645-040 part number gasket will not work?
I get the block back on Friday. Should I exchange the gasket for a 60 over or bigger gasket?
Thanks much for the help, I should of not assumed that a 40 over bore would require a 40 over gasket
You could.....but I wouldn't. I'd go with a 4.100" gasket......gasket hole at least .040" bigger than the cylinder bore.
KW
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On The Tree
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KW, I think(?) he's trying to say that the head gasket he's considering using has a .040" compressed thickness, not that it's 4.040" in hole diameter????
Last edited by 97 6speed z; Jun 14, 2016 at 05:51 PM.
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I just called cometic, and gave them the part number I ordered. They said that it is the correct gasket for a 4.040 motor. They said that the gasket measures 4.055. And is .040 compressed thickness.
Is 4.055 enough space for that bore like they say? Or should I send them back and go bigger
I just called cometic, and gave them the part number I ordered. They said that it is the correct gasket for a 4.040 motor. They said that the gasket measures 4.055. And is .040 compressed thickness.
Is 4.055 enough space for that bore like they say? Or should I send them back and go bigger
Is 4.055 enough space for that bore like they say? Or should I send them back and go bigger
KW