Excessive piston to wall clearances on KB944s?

[go4lo]

I looked at the instruction sheet that came with my IC944s last night and it's the "burnt orange/red" bordered sheet. Are you guys saying that it's the wrong one? Why would KB send the wrong instructions? It's not like I got these a year ago, I just ordered them 4 weeks ago so have changes been made since then?

[gonridnu]

I got mine a couple weeks ago and they had the wrong instruction sheet...a mistake in the packaging department.....check out the blue one I posted and then call KB with the production date on your box just to be sure

[fannman]

i got the blue border instruction sheet with mine and a production date on the box says 04-12 so i had machine shop hone to 3 thou but was informed by the guys at 505 that i should hone to 4.5 thou,they say it will have scuff issues that tight,i was really kinda pumped at a better forged alloy that could be ran a little tighter,im glad its still at machine shop,i need the skinny on this quick,i went round and round with the machine shop guy on the finish hone of 3 thou and he wanted to go bigger,now im really gonna sound dumb when i tell him to put the block back in and hone it more.

[Cheromaniac]

A 3.0-3.5 thou clearance is all you need for the IC944 pistons so leave yours as it is.

[SilverXJ]

Ideally 2.5-3.0 would have been fine for a street engine. 4.5 is a bit on the lose side but should be ok. Nice job 505.

[Retlaw01XJ]

The machine shop guy should call K-B and get the facts before he screws up any more customers engines.

[Cheromaniac]

Well, it seems that 505 Performance may have been at least partially right. Take a look at this page:

http://www.kb-silvolite.com/icon/clearance_pop.php

It suggests a piston-to-bore clearance of .0035" - .0045" for normally-aspirated street engines with a bore of up to 4.110" so there you have it.

[SilverXJ]

I believe that is for the 2816 alloy. Unless KB changed it again the IC944s are 4032, which requires less clearance.

[Retlaw01XJ]

Instruction sheet for the pistons I bought in November 2011 show 4032 alloy, 0.0025-0.0035" clearance for Street Normally Aspirated, bore size 3.5" to 4.1".

Icon forged pistons are 2618 alloy and use the larger clearances

We have the Icon FHR pistons which use the 4032 alloy and require less clearance.

Here are the instructions for our pistons:
http://www.kb-silvolite.com/assets/fhr_installation.pdf

Wonder what 'FHR' means?

[fannman]

called icon this morning and talked to tech rep and was told i would be fine with 3 thou,i will find out soon enough,right now im checking other clearances,just got block back from machine shop and checking the quench and its just righ,t i am right at zero deck.

[SilverXJ]

That was the sheet I was trying to find. I knew it was blue.

FHR = Forged Head Relief

[Retlaw01XJ]

FHR = Forged Head Relief

Okay, but what does 'Forged Head Relief' mean?

[gradon]

Pistons are domed/flattop/shallow dishes and have reliefs in the piston tops(heads) so that the valves don't touch them? The reliefs are forged instead of machined cut after the forging?