Boost Psi & Compression

Grabbin' Asphalt

5 Year Member
Jun 10, 2013
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Atlanta, Ga
If i were to consider adding some psi boost in a SC form down the road, what is my psi limitation with my "P" heads milled .030, is my compression in the range of 9.7:1 - 10:1?? ...would that work with only 5-6 psi or could i do 8psi with a intercooler and still be safe with a good tune?
 
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The V3 Si is the perfect blower, the compression isnt that much of a problem with 8-10lbs of pressure aka stock pulleys if the tune is good intercooled or not. If it is something you are concerned about you can just use a thicker head gasket but I wouldnt sweat it. I would just use the factory Vortech upper and lower pulley combo and have the tuner creep up on timing especially under peak rpms since most guys tune for WOT and dont play with 1/2-3/4 throttle bursts or acceleration areas and thats usually were a street guy will run into issues unless they ride the rev limiter too much first. If you decide to go Vortech let me know I get pretty good hookup with them ;) either way good luck and have fun!
 
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The V3 Si is the perfect blower, the compression isnt that much of a problem with 8-10lbs of pressure aka stock pulleys if the tune is good intercooled or not. If it me a is something you are concerned about you can just use a thicker head gasket but I wouldnt sweat it. I would just use the factory Vortech upper and lower pulley combo and have the tuner creep up on timing especially under peak rpms since most guys tune for WOT and dont play with 1/2-3/4 throttle bursts or acceleration areas and thats usually were a street guy will run into issues unless they ride the rev limiter too much first. If you decide to go Vortech let me know I get pretty good hookup with them ;) either way good luck and have fun!

I've heard a few youtube vids on the Sci and Si and the Si with 8psi sounds way quieter and I like that one a lot. I really don't like the look of the I/C though, would like something other than that set up.
 
If it makes you feel better I am throwing head gaskets , arp head bolts and an s trim on a stock motor with 10/12 lbs going through it in a few mos will be all together
 
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His heads are iron too. I still think you will be okay with mild boost, but the aluminum heads will tolerate a little more compression and boost than irons.

Joe
 
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The V3 is an entry level kit, that is installed properly on a well maintained and functioning engine will provide you with a safe, reliable increase in HP. The problem I see guys run into is the "it's never enough" syndrome. They start swapping out pulleys for more boost and then at 12lbs wonder why their head gasket lifted. At 10:1 you are a little high on the compression, as stock is more like 9:1. You can get around that with either a tune and/or a meth system.
 
I would say tops of 11.8 for your a/f ratio's

(for the record 9.5:1 compression and 35 psi of boost, we broke the cylinder head before we had a gasket failure.... just saying) It's all in the tune up my friend.
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