Back story: Rebuilt my 4.0 that had overheated and blew head gaskets. Full tear down. All new seals, gaskets, rings, and bearings. Decked heads and block. Honed cylinders. Pulled vaccuum. Reassemble. Bada-bing Bada-boom.

After 3000 miles I still had excessive blow by and loss of power.

Pulled the motor and took it back to the same shop, this time with the RAVE. Turns out my cylinders are spec'd out to grade B pistons and I have grade A. So here are my options:

Buy Grade B pistons- $526
Buy aftermarket +.020" pistons- $175
OR teflon coating on the sides to close the .003 gap.- $250

Thoughts and opinions?

 

Is there an option for oversized rings or is the gap too much for them to be effective? Just a thought. D*

 

I'd get the aftermarket pistons ... only because you can replace them with the engine in the truck.

 

Did you use Hastings piston rings? I believe that's what aluminum v8 sells. Every set of Hastings rings I've encountered was at max ring gap out of the box. Whatever brand RovahFarm sells that is in the 3 vacuum sealed bags required grinding.

 

Daryl- I have not found oversized rings. But the clearance issue is between the pistons themselves and the cylinder walls.

Charlie- I went this route but the motor is already pulled and at the machine shop.

I used Rovah and had the machine shop do any adjusting of rings and such.

Last week I ordered 94mm pistons (type B). I didn't trust the Teflon coding and didn't want to risk over bore pistons with our thin cylinder walls.

Wife has officially signed off on finding a Ford 3.5 ecoboost with tranny and bringing it home. Getting this motor running and operational will allow me to drive it while I start the prep work for the swap. super excited!

 

thank you for sharing with us .