compression question

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Dec 27, 2010 | 04:46 PM

Chevyboy82188

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compression question

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?

Dec 27, 2010 | 05:03 PM

PREDATOR-Z

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From: BFE

Is this a boosted application?
What size reliefs in your pistons?

Dec 27, 2010 | 05:19 PM

Chevyboy82188

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yes going to be running a borg warner s472 turbo. My pistions have a -1.6cc

Dec 27, 2010 | 05:32 PM

PREDATOR-Z

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From: BFE

You should have got deeper piston reliefs. Even with .060 gaskets, you'ld still be at ~10.4:1

Dec 27, 2010 | 05:42 PM

Chevyboy82188

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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....

Dec 27, 2010 | 05:52 PM

speedtigger

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Nothing more reassuring then doing your own math:

http://www.rbracing-rsr.com/compstaticcalc.html

Dec 27, 2010 | 06:08 PM

Chevyboy82188

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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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Dec 27, 2010 | 06:33 PM

speedtigger

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What are the CCs of your current heads?

Dec 27, 2010 | 07:36 PM

Chevyboy82188

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317 heads will be 72cc

Dec 27, 2010 | 08:09 PM

#10

Chevyboy82188

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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.........

Dec 28, 2010 | 12:12 PM

#11

PREDATOR-Z

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From: BFE

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.

Jan 15, 2011 | 11:03 PM

#12

Chevyboy82188

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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..........

Jan 16, 2011 | 08:07 AM

#13

35th camaro

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Sure sounded like you were asking for advice

Jan 16, 2011 | 11:27 AM

#14

speedtigger

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So there! LMAO

Jan 17, 2011 | 05:40 PM

#15

PREDATOR-Z

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From: BFE

Quote:

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

Last edited by PREDATOR-Z; Jan 17, 2011 at 05:48 PM.

Jan 17, 2011 | 06:42 PM

#16

cacmanjr

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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?

Jan 17, 2011 | 06:56 PM

#17

TA63

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Quote:

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?

Jan 17, 2011 | 07:34 PM

#18

PSnewbie

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Wouldn't thicker head gaskets be more prone to failure on an FI motor?

Jan 18, 2011 | 02:53 PM

#19

PREDATOR-Z

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From: BFE

Quote:

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)