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compression question

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Old 12-27-2010, 04:46 PM
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I have a 383 ls1 with a 11.1 comp ratio im going to put on 317 heads to drop it to 10.1 so what head gaskets should i use to get me to ~9.5cr?
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Old 12-27-2010, 05:03 PM
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Is this a boosted application?
What size reliefs in your pistons?
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Old 12-27-2010, 05:19 PM
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yes going to be running a borg warner s472 turbo. My pistions have a -1.6cc
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Old 12-27-2010, 05:32 PM
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You should have got deeper piston reliefs. Even with .060 gaskets, you'ld still be at ~10.4:1
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Old 12-27-2010, 05:42 PM
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how is that? im told that the 317 heads will drop my comp 1 point? that would take me to 10.1....
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Old 12-27-2010, 05:52 PM
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Nothing more reassuring then doing your own math:

http://www.rbracing-rsr.com/compstaticcalc.html
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Old 12-27-2010, 06:08 PM
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not 100% sure on the numbers quite yet but with my setup and .060 headgasket i should get a ~9.6 comp ratio?
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Old 12-27-2010, 06:33 PM
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What are the CCs of your current heads?
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Old 12-27-2010, 07:36 PM
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317 heads will be 72cc
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Old 12-27-2010, 08:09 PM
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I think my motor is 11.4:1 so with those heads and a .086 gasket gets me to 9.8:1.........
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Old 12-28-2010, 12:12 PM
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You can't just run any gasket thickness you want. .060 would be max. That is why I mentionned it.
My advice is do some more research on your motor and try to understand its limits.
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Old 01-15-2011, 11:03 PM
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Dont worry im not askin for your advice went and talked to a good engine builder/machine shop he ordered me .70 gaskets to get 10:1 he said im fine..........
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Old 01-16-2011, 08:07 AM
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Sure sounded like you were asking for advice
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Old 01-16-2011, 11:27 AM
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So there! LMAO
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Old 01-17-2011, 05:40 PM
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Originally Posted by Chevyboy82188
Dont worry im not askin for your advice went and talked to a good engine builder/machine shop he ordered me .70 gaskets to get 10:1 he said im fine..........
Best of luck on your build, just don't drive with the same attitude, you'll hurt somebody
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Old 01-17-2011, 06:42 PM
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Guys, I don't mean to hijack the thread but I have a question related to calculating compression. What is the stock deck height on an ls1. I have read that the piston sticks out of the hole. Is that true? By how much?
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Old 01-17-2011, 06:56 PM
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Originally Posted by Chevyboy82188
Dont worry im not askin for your advice went and talked to a good engine builder/machine shop he ordered me .70 gaskets to get 10:1 he said im fine..........
You want a tight quench to reduce the possibility of detonation, esp with forced induction. Might want to rethink this a little. Maybe see if your shop can open up the combustion chambers on the 317's 3-4cc's each?
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Old 01-17-2011, 07:34 PM
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Wouldn't thicker head gaskets be more prone to failure on an FI motor?
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Old 01-18-2011, 02:53 PM
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Originally Posted by PSnewbie
Wouldn't thicker head gaskets be more prone to failure on an FI motor?
That too, but I've seen Nelson motors holding fine with .060 gaskets if done right. Mainly as mentionned you want to limit detonnation, to do so, the right quench is preferable (to benefit from maximum timing advance)
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Old 02-04-2011, 04:15 PM
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what exactly is quench? Is that the relation of the piston face to the head surface?
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