Icon piston clearance

[RenoF250]

I am planning to run IC944 pistons but I am getting very mixed signals on what the clearance should be. Piston vendor says hone to 5.5 in the back 3 and 5.0 on the front to prevent seize. I called Icon and the guy I talked to said the clearance was in the piston and just hone to 3.905 exactly and it will be right. He was adamant that seizing was some other problem and not the piston. He said the alloy replicates the expansion of a regular cast piston.

This disagrees a bit with the Icon piston install guide that shows a clearance range of 2.5 - 9.0 depending on material and application.
IC944 are premium line so they should be this:
https://www.uempistons.com/installation ... lation.pdf
But the material is supposedly 4032 so they would be this:
https://www.uempistons.com/installation ... lation.pdf

What are those of you running the Icons using for clearance? Anyone have a seizure? I cannot find a clear answer on this, I am starting to think of just leaving it a 4.0.

[Retlaw01XJ]

Use the second sheet. The IC944's are FHR series pistons. Should be included in the box with the pistons.
I can't comment on whether the clearance is 'built-in' to the piston spec, but standard procedure would be to get the pistons, measure them, add the clearance and bore/hone to the proper size.

I've read a comment or two here about #6 running hotter. Dunno if it's significant, but I'd guess it's not. Add a turbo or other supercharger, and maybe it's a different story.

[SilverXJ]

I called Icon and the guy I talked to said the clearance was in the piston and just hone to 3.905 exactly and it will be right.

No way would I do that. Measure piston then hone for clearance.

https://www.uempistons.com/installation ... lation.pdf

This sheet, the blue one is the correct one.

What are those of you running the Icons using for clearance? Anyone have a seizure? I cannot find a clear answer on this, I am starting to think of just leaving it a 4.0.

Mine was at 4, but when i had all the cam bearing failures I had it rehoned and ringed to around 5. Which would put me right where I need to be for FI. Its a bit loud in the winter (~30*f and below)but after a couple minute of driving it quiets down. Its better to be on the lose side than the tight side, as they say only you know its loose, everyone knows if its too tight.

[RenoF250]

I called Icon and the guy I talked to said the clearance was in the piston and just hone to 3.905 exactly and it will be right.

No way would I do that. Measure piston then hone for clearance.

https://www.uempistons.com/installation ... lation.pdf

This sheet, the blue one is the correct one.

What are those of you running the Icons using for clearance? Anyone have a seizure? I cannot find a clear answer on this, I am starting to think of just leaving it a 4.0.

Mine was at 4, but when i had all the cam bearing failures I had it rehoned and ringed to around 5. Which would put me right where I need to be for FI. Its a bit loud in the winter (~30*f and below)but after a couple minute of driving it quiets down. Its better to be on the lose side than the tight side, as they say only you know its loose, everyone knows if its too tight.

Did you have any piston problems at 4? Anything to indicate there was problem brewing?

I agree, I think I will have the machine shop wait until I have pistons so he can hone to size.

I am really getting down to only one place saying to hone over 5. I called another supplier today and they said they do 3 and have not had any problems.