1 year ago bought a 95 gs 420a that was totalled and rebuild it from the hood, bumper, fenders, lights, radiator and engine frame. After that things went well until I installed a 420a turbo, intercooler, new clutch and rear main seal and was running very good. The problem is after installing the turbo I ran the car at 6 pounds boost and liked it; however, I decided that I wanted more boost. So without reignforcing the engines internals except for the rear main seal, performance clutch and new head gasket I slapped 8 pounds to the turbo and was starting run better and better until I pushed 12 pounds and that was when things started to go wrong... Oil begun blowing by the stock pistons out the very top of the engine and getting things messy. Now it is in the garage again. The engine still runs and drive decent but the top of engine won't hold compression when turbo spools up and the head needs to be replace. After putting so much into a car that I love and want to keep running after all it has been through; my question is. In the case of a 420a engine with stock internals that relates to anything and everything, rebuilding a engine is something that I have never done, but am going to do this winter. So when I am finished I will work this 420a turbo to push and hold up to 20 pounds... So what are you thoughts, concerns, comments, and what additional parts will I need for this rebuild???

I'm not sure what you're really asking....but I guess start here:

http://www.2gnt.com/www/corbin/rebuild.html

Besides forged internals for your rebuild, you will need a very good fuel setup. MSnS or Portfueler are proven ways to be able to handle 20+ psi.

Originally posted by a420aturbokidd
The engine still runs and drive decent but the top of engine won't hold compression when turbo spools up and the head needs to be replace.

Replacing the head isn't going to fix the piston you cracked.

Originally posted by DarkOne
Replacing the head isn't going to fix the piston you cracked.

Stock internals are only good to about 8psi through a FMIC set up. (Assuming an HRC S16G with the 10cm^2 housing.) If you have a T3/T4 hydrid, you should have stuck with 7psi or so.

Now you're going to have to replace your pistons, rods, and rings. Might as well replace the bearings while you're at it. Other common things to replace are water and oil pumps, all your belts and hoses.

Find a used head in good condition. Have it decked for the gasket, the valves at least lapped, and replace the seals. You've got a big project ahead of you, so don't spend money on upgrading the head unless you're sitting fat and want to.

Good luck.

Yeah do forged internals, dont be dumb like me and run on stock internals with a turbo and crack a cam :/

Originally posted by Flipboi89
Yeah do forged internals, dont be dumb like me and run on stock internals with a turbo and crack a cam :/

How exactly does running stock internals cause you to crack a cam... :scratch :rolleyes

I would have worded that question differently trickee....


Damn those manual boost controllers. Atleast you weren't being a pussy and decided to see what YOUR engine could take. Did you step it up 1 psi at a time or just crank it straight to 12? Just curious. Not that i'd like to do that to my stock bottom end. You're lucky you didn't shoot parts everywhere.