More than 17psi?
More than 17psi? I've heard from a couple different people that the heads start lifting after 17psi on boosted applications. Is there any truth to this? I see a couple people on here running more than 17 and they don't seem to have a problem.
Thanks.
Thanks.
Staging Lane
Joined: Oct 2003
Posts: 81
Likes: 0
Originally Posted by Shane_G
I've heard from a couple different people that the heads start lifting after 17psi on boosted applications. Is there any truth to this? I see a couple people on here running more than 17 and they don't seem to have a problem.
Thanks.
Thanks.
SSU Moderator
Joined: Nov 2001
Posts: 4,857
Likes: 0
From: Austin, TX
yes...exactly at 17.1psi...on any combo, regardless of tune, air flow, and backpressure. What sense does that make?
Detonation makes heads "lift." Although it seems the whole notion of the word LIFT is a misnomer. At worst you put INTENSE pressure/heat around the head and warp the contact surface, but I don't know if anyone (except for Rob at QMP) actually having a head fail and lift itself off the surface of the block, trashing the head bolt/stud area. With AFR/AllPro/Dart heads and their thicker surfaces, plus headstuds, I don't see that happening again. Now, hot spots due to detonation will put holes in any combo.
Detonation makes heads "lift." Although it seems the whole notion of the word LIFT is a misnomer. At worst you put INTENSE pressure/heat around the head and warp the contact surface, but I don't know if anyone (except for Rob at QMP) actually having a head fail and lift itself off the surface of the block, trashing the head bolt/stud area. With AFR/AllPro/Dart heads and their thicker surfaces, plus headstuds, I don't see that happening again. Now, hot spots due to detonation will put holes in any combo.
i wouldn't say 'x' amount of boost lifts heads, its more based on the actual cylindrical pressure that lifts the heads and causing gaskets to pop out. There is a theoretical max threshold that the heads will stay down , even with a good tune. w2w is a perfect example with their 6 sec car. Their car lifted the heads but they are pushing what almost 1600 hp, lol.
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SSU Moderator
Joined: Nov 2001
Posts: 4,857
Likes: 0
From: Austin, TX
Originally Posted by Got Me SOM
i wouldn't say 'x' amount of boost lifts heads, its more based on the actual cylindrical pressure that lifts the heads and causing gaskets to pop out. There is a theoretical max threshold that the heads will stay down , even with a good tune. w2w is a perfect example with their 6 sec car. Their car lifted the heads but they are pushing what almost 1600 hp, lol.
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Cylinder pressure and the tune lift's the heads.Our shop race car lift's the heads every racing event because we run high compression,high boost.No big deal changing the gaskets 