Andy1

I'm trying to get a feel for (turbo) boost levels on a 4.8 with stock internals (not for racing application). Searching lead me to lots of LS1 discussions. The general consensus seems that 5psi is about the safe limit on internals for those motors (of course, part of the consideration is they start with a little higher CR). They consistently site the pistons as the major weakness. The 4.8 being lower CR, and a shorter stroke is helpful; perhaps this is the ingredient that makes the difference (lower piston speeds?). I'm not sure what exactly I'm asking, but perhaps some feedback from those that have BTDT.

Thanks,

Andy1

parish8

iTrader: (6)

bone stock 4.8, never opened. 10+psi on pump, cant remember for sure on that one and as much as 22psi with race fuel. not saying it would last forever that way but i took it out several times with a total of 50 or so runs at 20psi and it was still running strong.

there is a nice post from when i went to the dyno, let me find it.

parish8

iTrader: (6)

https://ls1tech.com/forums/showthrea...highlight=dyno

https://ls1tech.com/forums/showthrea...highlight=dyno

Black Blown 02

You could probably run 5psi and a bad tune (lean, too much timing) and melt a piston in a few runs.

You could also probably run 12 psi for a long time with a good tune and have no problems. The tune is definately the important part.

Andy1

Of course you are right. Any forced induction system requires appropriate fuel and spark management (tune), and I plan on providing that. That said, do you still think I need to be concerned with piston failures, rod bolt failures, or? Parish8 seems quite comfortable with boosting to higher levels on stock internals. Any idea why the LS1 guys are so concerned with their stuff? Maybe truckers are a lot more brave

Andy1

Black Blown 02

I think with a wideband and a datalogging program, stock internals will go a long way. They seem pretty strong from what guys on here are throwing at them.

Procharged LM7

I have almost two years on my stock 5.3 internals.
I usually only see up to about 7 psi, but have spun it to right under 10.
My fuel tune is all good, but I still se KR and need to lower timing tables.