My motor is now to the machine shop and the guy need the wall clearance... since I bought the pistons with 1000 miles on them from a member, he did not give me any sheets. And the machanic does not know the 420A so well... he knows the 4G63 but was no clue with the 420A.

Mine are 0.020 overbore and 8:8:1 compression.

Ive read some place with 0.0030, other with 0.0035, and 0,0040.

What I need to say exactly to the guy ? And if someone have a scan of that sheet that would be perfect.

Thanks !

For a boosted street engine, set the JE piston to cylinder wall clearances to 0.004".

Originally posted by noboost
.0038" is too small. .0040" works but I think it might be too small .0045" is what I'll be trying next time.

Do you have any evidence or are you just guessing?

I have a set of used JE pistons sitting here on my shelf that had a clearance of 0.004" for 3 years of use in a single 420A engine. They've seen nitrous, 30 PSI of boost from a 20G, and coolant temps of well over 250 degrees (not all at the same time of coarse)... and there's absolutely nothing abnormal about the wear that they show. Actually, I'm getting ready to install them into another engine. The only time I heard any piston slap was during startup on a 10 degree winter morning.

So, why do you think 0.004" might be too small? Why is 0.0038" definetely too small (only 0.0002" smaller)?

When you said 0.0040 its the space between the pistons and the wall ? So its about 0.0020 on each side ? 0.0038 will egual to a more tight space ? I know JE will expend with heat, on the scanned sheet I see 0.0040 but cant read all information I need a little more on the right of the sheet :/

Thanks for the scan

Yeah, the piston to cylinder wall clearance is the difference between the cylinder diameter and the piston diameter.

Originally posted by dougie2
Yeah, the piston to cylinder wall clearance is the difference between the cylinder diameter and the piston diameter.

Said that to the machanic today, he was a little scared of that big clearance but since its JE and they are forged... it should be good.

Not for nothing but, I just spent all of 15 seconds on google search, then click onto site, and then this page;

http://www.jepistons.com/dept/company/

Wouldn't that have been a lot quicker and less worriesome?

MB

Already saw these phones number, but I dont speak so well in english. Btw the andwer today to an email and they also said 0.0040.

Oh and by asking it here... all ppl will be able to see the spec sheet now!