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aluminum rod piston to valve clearance

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kinda-stock

Proven Member
55
0
Jun 4, 2016
jefferson, Louisiana
i have manely pistons and groden aluminum rods. i know factory limits on piston to valve clearance is .080" but what are the clearance recomended for aluminum rod setups
 
The rule of thumb is .030". That has since been reduced to .010".

Here is a great read.

http://www.dragzine.com/tech-stories/engine/debunking-aluminum-rod-myths-with-grp/

And with that we only run GRP rods as they are local to us. And have had no issues up to 10,500rpm. We had the same engine together for three years before it crankwalked. We had lots of passes and way too many hours in the dyno trying to figure the car out. With up to 57psi and a 300shot of nitrous from an 83mm turbo. I checked valve clearance upon install and never worried about it after that.
 
wait, why would aluminum rod engines require .030" clearance and normal steel rods require .080"? everywhere online says aluminum will stretch more due to thermal expansion
 
I believe he meant in addition to the clearance you'd normally run. If you read that article, .010 additional clearance is what the guy from GRP was recommending.
 
Last edited:
Yes. Sorry. 010"-.030" more depending on who you talk to. For what it is worth, I have never made any significant changes for an aluminum rod motor. I assemble it just the same and a have never head issues. I usually run a special piston and as thick a head gasket as I can get my hands on and never have had to worry about a thing. We have been using aluminum rods since 2005 and have not had issues. I have done plenty with off the shelf pistons and head gaskets and not run into any issues yet. I agree with the article that those myths of aluminum rods have long since been gone with technology. I know if quite a few locals who have 10,000, 20,000 even 30,000 miles on their aluminum motors and have never touched them. At high horsepower.

If it concerns you modify your pistons(fly cut people like to call it) and try finding a 1.5-2mm thick head gasket. Problem solved. As stated, never had an issue even with off the shelf parts. I run large lift cams, so Arias made me my own special piston with deep and larger reliefs. Got my own little part number with them.
 
Correct. i purchased these rods from Keith back in 2009. As we all know life jumps in the way of car projects but i am relentless to get the car back on the road.

I am fly cutting one piston at a time. Only did one so far and I am good with the results. Only the intake side of the piston needed massaging. My P/V clearance is now .158" on piston #1
 
piston #1 so far.
 

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