How much boost?

[ponjohn]

How much boost can stock shortblock take and be reliable?

John

[chicane67]

Without "O" ringing the block... ?? I'd say about 6 to be anywhere near reliable.

[WS6]

Are we talking truck motor, be it a 5.3 or 6.0 or are we talking car motor LS1/2/6?

[ponjohn]

Car ls6.

John

[WS6]

6-7psi properly intercooled and you should be fine. Of course it will depend on just how hard you drive the car. I have a customer with an 03 vette and we did his Pro-Charger when he had maybe 1500 miles on the odo. I rarely hear from him as he is very busy and has had no issues. Last time I talked with him he was over 20k and loving it. He runs it hard from time to time as well. He loves running Ferrari's on the interstates around ATL. They never expect him to keep up.

[chicane67]

He loves running Ferrari's on the interstates around ATL. They never expect him to keep up.

That's kinda surprising... Ferrari's are not all that fast to begin with.

[WS6]

haha this is on the interstate from a roll. Besides, his car was built before the Stage 2 system was ever available, so his car only makes 450rwhp/400 ftlbs. Now my customer with the 04 Z06 and Stage 2 Pro-Charger makes 540 at the wheels and has 3.90 gears. His first and second gear are nearly useless under boost, but on the interstate the 3.90s are very fun.

[ponjohn]

With a stick shift; do you think a gross calculation can be based on 15% loss?

John

[justforfun]

I have been told to replace the head bolts if you go past 7psi.

[nitrorocket]

With head bolts and 6.0 gaskets you can do 10 psi with a low (6,000) redline. Forged rods, pistons and studs will do 25+ psi.

[WS6]

Head bolts are cheap insurance. My numbers were based on using the same heads the engine came with. Nitro is right though about using 6.0 heads on an LS6. I completely forgot about going that route.

[WS6]

With a stick shift; do you think a gross calculation can be based on 15% loss?

John

Yes, but you might as well figure 18-20% so you can be surprised and feel better when you go over that number.

[streetk14]

That's what I did, swapped the LS6 heads for a set of cnc'd LQ9 6.0 heads. For those who don't already know, the LQ9 head is almost identical to the LS6 head but it has 71 or 72cc combustion chambers that will make your compression ratio a little more boost friendly.

As a side note, there are guys running 12-14 psi on stock LS1 shortblocks with good results. Are these motors going to last forever? Probably not, but it can be done with careful tuning. I'm looking to run 10 psi on mine, but am having some belt slip issues right now that are keeping me at 6 psi.

Andy

[[email protected]]

We typically see stock short block failure somewhere in the 550-600RWHP area. Turbo cars seem to be on the higher end of the spectrum, and blower cars on the bottom end.

That being said, we have had them fail below 550, and had them last over 600 too

[ponjohn]

Fail in the sense that the block fails?

John

[[email protected]]

Block and crank rarely fail before a piston/ringland or rod will.

[nitrorocket]

It is almost always #7 piston lands that go first, then the rods. Change both out with forged units and you will have a virtually bulletproof motor.