We all know that boost on a stock bottom end will = rebuild. What happens when the stock bottom end usually quits? Does it show any symptoms first such as blowby? or will it end with catastrophic engine damage?

If I can get by with 7-8#'s, bigger injectors (no fmu), and a good dyno tune (on the rich side), I may go supercharged for just a while until I can save enough for the rebuild. I'm mainly worried that the stock internals are just going to let go and damage the motor.

Thanks,
Adam

 

Might damage the motor, might not, kind of a crapshoot IMO.... Pistons would be the most likely culprit. I was taking apart an LT1 shortblock only to discover that one piston had broken ringlands/rings. All of the pieces had been contained very well within the rings, and the cylinders werent damaged. I looked at the oil pump gears and there was no damage on them (I've seen what those gears look like after they pick up any small pieces). The bearings in the motor were also in good shape (for a high mileage LT1 anyway, point being no problematic damage)... So in a case like that you wouldnt damage the motor, but my guess is that it was blowing by a good amount, and likely wouldnt pass a leak down or compression test on that cylinder. All of that being said, a piston might break and go into the bottom end and cause the motor to self destruct. Could even break the top of a piston, have it hit the valvetrain and then the entire motor could self destruct...

 

Adam -

Your bottom end should have no problem withstanding that much boost.

However, your REAL problem is going to be detonation. Simply running a rich mixture isn't enough to crutch that. Bottom line...? If you want to do it, go ahead, but you'll need higher octane fuel.

I personally use a blend of gasoline and toluene in a 4:1 mix. My engine isn't currently supercharged though. You may need a 3:1 or 2:1 mixture on boost.

Just remember that toluene is 114 octane and mix appropriately.

Something else to keep in mind is; if you buy a small blower NOW to make the small boost you want, will it be big enough for your rebuild later on? Ask the blower company what they think.

 

Well I might just cross my finger's and go for it...if it goes, it goes. I'll take every precaution to spin the bottom end as safely as possible. And if it DOES go out, it's not my only daily driver so I have no problem parking it until I can rebuild it. Hell, I'll probably even park it if I start getting any blowby. (I'm trying to convince myself, as if nobody can tell.)

lamerandom- you bring up a pretty good point about the toluene...I'm pretty sure theres a local speed shop that carries it. But how would I keep tab on the correct mixture without drying my gas tank out before I fill up again?

I also plan on running an ATI P1-SC, I think that would be a good blower for a forged 355 in the future, with a different pulley of course.

 

Two friends and I all ran 6 psi non-intercooled Vortech S Trims and all 3 of us took out the rings lands on multiple pistons. No damage to any of the 3 engine blocks. Start saving for your rebuild.

 

Here's a page with some good info for you:

http://www.gnttype.org/techarea/misc/octanebooster.html