Piston to cyl. clearance Help!!!

[sprocket2005]

I am rebuilding a 4g63 with mahle 285 gram pistons. I do not know what the ideal clearance would be from piston to cyl. with pistons that are so light. I called Slowboy racing and Mahle and got two opposite answers. Slowboy says the clearance needs to be tighter than stock spec, but when i called Mahle they said it needs to be looser than stock spec. I do not know what to do. The assholes at the machine shop that has my block want to set it at 20 thousanths. 20?? Thats a bit extreme isnt it? Somebody help me out. What should i do?

OK, i went to the machine shop and talked to the guy who's working on my motor. He said the clearance is a tight 0.002, but one of cylinders is scratched. He said that he's gonna hone the cylinder and the scratch will be gone, but the clearance will be about half to one thousanths bigger than it is now. I also talked to Mahle's tech guy again and he said the clearance should be 0.002, but being a little looser wont hurt any. Does that sound right?

 

[tbonitz301]

.o2o isnt much at all. maybe little thicker than a hair. Are your pistons forged?

 

[Burnett03]

Why don't you follow what Mahle said? I mean they do make the pistons. Seems logical that you would follow what they say? If they are forged, which i'm sure they are, then yes you want to go a little looser, but not to loose because they could slap.

 

[coryd]

Why don't you follow what Mahle said? I mean they do make the pistons. Seems logical that you would follow what they say? If they are forged, which i'm sure they are, then yes you want to go a little looser, but not to loose because they could slap.

and slowboy has built how many 4g63t engines??

 

[Burnett03]

and slowboy has built how many 4g63t engines??

And your point? Mahle MAKES the pistons. Don't you think they would know what the proper clearance is? Have you read any threads about slowboyracing and how they run their business? Cylinder clearance should be set based on goals. Boost, nitrous etc. I wonder if slowboy even asked them his goals, or if they just said "Tighter than stock"

 

[tqmx1]

^^^+1^^^ Mahle made the pistons go by there specs. Every set of pistons I have seen (after market) should have a sheet that comes with it giving the clearances.

 

[1992awdlaser]

.0015-.002 is what I have heard for Mahles. I would go on the little bit looser side of those specs for the most power but there will also be an increased risk of blowby. I would probably set them to .0018.

 

[Slowboy]

If your machinist wants to call me - I can help him.

Mike Huml
724-349-8417 ext 13