Streetable compression?
10-27-2003, 02:55 PM
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Streetable compression? As most of you know my 382 Stroker broke a timing chain last week. We got the heads off today and got them to my head porter. Outta 16 valves all but 4 were bent. Im gonna have some cool paper weights for my desk.
My engine builder did the math and we found out the compression is right at 12.78 to 1 mighty high for pump gas and texas heat. I need to lower the compression. We are looking at some Cometic gaskets with a .60 crush size. Which should bring the comp ratio to 12.2 to 1. Is this streetable?
My engine builder did the math and we found out the compression is right at 12.78 to 1 mighty high for pump gas and texas heat. I need to lower the compression. We are looking at some Cometic gaskets with a .60 crush size. Which should bring the comp ratio to 12.2 to 1. Is this streetable?
10-27-2003, 03:09 PM
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Im not going to get that number unless i buy another set of heads. I mean even with the 12.78 compression i only had knock at WOT. What if I just reduce timing or should i just bite the bullet and have another set of heads done?
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10-27-2003, 04:06 PM
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Originally Posted by Jamie33
this might be off the topic, but why dont you just buy some better gas? or even octane booster or something
However, if it's a weekend fun car, that might be a good solution. With the 93 octane in Texas, it shouldn't take much in our little 16 gallon tanks to get the octane rating up enough.
10-27-2003, 05:04 PM
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I think you're in a rough spot.. even if the 12.2 would work, with the .060 gasket, you're really openeing up the quench height. At tdc, does your piston sit flush with deck surface, or is it out of the hole? If your quench height(distance from piston face to head face) is greater than about .05-.055, your engine will become LESS able to tolerate the same compression ratio than one with a tighter quench like .04-.045. Good luck
Bryan
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10-27-2003, 05:14 PM
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10-27-2003, 05:23 PM
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why mess with the pistons? a simple head change, or some port work to open up the chamber size would be ideal here. there's no sense in fooling with the integrity of your bottom end.
10-27-2003, 05:29 PM
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I run a 12.2:1 CR on Ca 91 pump gas....tuning is a great thing 
I have no knock at WOT, I'm running approximatley 17* of timing right now. I basically have my street tune, then a race tune for 25* of timing and 103 octane.
I have no knock at WOT, I'm running approximatley 17* of timing right now. I basically have my street tune, then a race tune for 25* of timing and 103 octane.
10-27-2003, 10:13 PM
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The block was decked .20 and the heads were already milled .30 when i had my porter clean them up and add bigger valves and he did mill them a tad. That plus the Lunati pistons = too much freekin compression!
10-27-2003, 10:35 PM
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hey, that might actually be good news.. are you running the ls-11 lunati pistons(flat top with falve reliefs), 6.125" rods, and 4" crank? do you have ls1 heads or ls6 heads? have they been cc'd? if so, what is the volume of the heads?
Last edited by FDLS6; 10-27-2003 at 10:51 PM.
10-28-2003, 07:12 AM
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FDLS6 is correct. If you have proper quench height at 12.78:1 and then add a thick gasket (increase quench height) to reduce your compression ratio, you will very likely end up with more detonation.
