My friend's JDM B18C blew a ring land and ring in the #4 piston. So he decided to go w/ lower compression pistons with his turbo. He went with JE 9:1 pistons 81mm (stock bore), eagle rods, and JE piston rings, JE wrist pins.
The piston rings were machined to specs and they were all placed correctly in the right place and w/ the "JE" stamp facing upwards.

It started up and idled like crap. Runs like crap too. Motor was never pushed at all. So from a leakdown test we found out that there was:

60% leak in cylinder #1
30% leak in cylinder #2
50% leak in cylinder #3
10% leak in cylinder #4

The head has been taken off and pressure checked and it came back fine. I also loaned him my head to test and it came back fine. Still it idles like crap and runs like crap. So what could be the source of the problem? Nothing looks out of the ordinary. Could it be a bad piston batch? Did I receive wrong rings? Thanks for the input.


Joe

 

I would check the rings; maybe they didn't set the end gap right? Scoured cylinder walls?

 

Cylinder Walls look fine. I put the JE piston rings against the OEM stock ones and the OEM stock ones had a slight, slight, slight, hair larger ring gap. Almost unnoticable.

 

were the cylinders honed for the new rings to seat properly?

 

My friend said that they weren't honed. Could that be the case that up to 60% of the air was leaking from the cylinders? Any tips on honing?

 

damn...........you will never get the rings to seal without honeing the cylinders.

pull all the pistons out and have someone who knows how to manually hone the cylinders give it a shot and hope that will cure your problem. but this is a mickey mouse type of a fix. to do it right you should have the engine removed and sent to the machine shop to have them measure and bore and hone the cylinders.

 

you dont have to hone the cylinders but you can break the glaze and knurl the pistons. cheaper.

 

We're going to pull the motor apart and take it to have it honed. The walls are smooth and glazed like glass. So is it because of the smooth texture that doesn't allow the new rings to seal?

Thanks for the info.

Joe

 

What's knurling the pistons? What type of material do you use to break the glaze?

 

for my first motor way back when i used a bottle brush 1mm over size to cylinder bore, with a cordless makita drill at low speed...a local machine shop told me to use dextron 3 (autotrans fluid) and half acetone mix in a spray bottle
even strokes ...dont spend to much time high or low...this could create some goofy tapers
was cheap to do ...cost about 30 bucks total
Good luck

i used this method and worked great
just dont forget to clean up the mess LOL

just my .02

 

yah u need to break the glaze on the cylinder walls. Go to an auto store and buy a flex hone. Just break the glaze that way. If its a high milage motor, you'll want to get it line honed.

If its really old, you'll be out of spec and need to go .5 over JE pistons.
so then a bore and line hone=perfect

basicly, new motor=flex hone or line hone
flex hone=30 bucks
line hone=100 bucks
bore and line hone=200 bucks