I originally posted this in LT1 Tech, but this is a better place so I'm putting it here as well. My apologies if you are seeing it for a second time.


The car is a 95 LT1 Z28 with a 5psi Paxton supercharger. Other than roller rockers the internals were completely stock.

Detonation destroyed 5 of the pistons, so the motor has to be rebuilt. The car is street driven, but raced a lot too.

1) Is there anything that should be changed or done to the motor before re-assembly?

2) What kind of pistons would you use? Forged or Hyperutectic?

3) Compression was 10.5:1 (plus whatever the Supercharger was adding). Should it be lowered?


Any help would be greatly appreciated

Thanks

 

Most of these questions can be answered with a simple search. Also you have a few variables left in the equation. How much boost are you plaining on running after rebuild? What power level do you want to reach?

 

Agreed, what kind of power are you wanting out of your setup?, need more info......

 

I agree that more info would be helpful in giving you the best answers, but a couple of thoughts.

1) Is there anything that should be changed or done to the motor before re-assembly?

How many miles on it? As long as you are rebuilding, at the least you should do rings and bearings. Honing may be needed, depending on the condition of the cylinders. A SC friendly cam is a lot easier to install when the motor is out/apart than in the car.

2) What kind of pistons would you use? Forged or Hyperutectic?

Forged, for sure.

3) Compression was 10.5:1 (plus whatever the Supercharger was adding). Should it be lowered?

At 5psi, maybe 9-9.5:1 would be good. If you want to run more boost, then even lower compression is a good idea.

Rich Krause

 

Well, right now the engine is totally disassembled, so things like rings and bearings are already going to be replaced... mileage was just under 40,000 miles. As for the boost, it'll stay the same, around 5psi. And there's no real power level in mind here, I'm not building it up to meet a certain power goal, but to get it back to the same approximate level as before (around 400 RWHP) but with better reliability (lower compression, better pistons, etc.).

While I'm at it, the other mods on the car are: 1.6 Roller Rockers, Edelbrock Headers, 3" Exhaust/Cat/Flowmaster, Spec Stage 3 clutch, 3.73 gears, and MSD Ignition with Boost Timing Control. MAF and TB were stock, as was mostly everything else.


Thanks for your help so far guys.

 

All Depends on how much power you wanna make. I would say go with good bearings. I use Clevite 77's. Go with a good forged piston like JE or SRP. Go rods or at least factory PM rods with good ARP bolts. Make sure you use studs on the main caps. The thing about supercharging is it gets addicting. You are gonna want more power, and more power is just a pulley or head unit swap away. If I were you I would over build now, because it is alot cheaper than building it up again when you want more boost.

 

Also...
A good tune is also key to make good power and also may keep you from doing Another rebuild sooner than you would like.

Thx,
Claude

 

If your plans dont involve anything over 12psi then I would probably run 9:5 compression. Speed pro just came out with a new line of light weight pistons instead of there old blower slugs. The new line of pistons now have the light weight, lowered ringlands, and forged aluminum for exceptional strength. I do believe that they offer the blower pistons in std, .030, .060 sizes. Im not sure if speed pro changed the dish in there blower pistons for sbc, but the blower slugs that speed pro use to, or may still, sell net about 9:1 with stock heads