.038" overbore 409 questions

[Gliderider06]

I have a .038" bored 409 and need pistons for it. It needs to be final honed and was wondering if I'm able to use the Icon .038 pistons? I don't know how much clearance is needed for them or do I need to just shop for .040" pistons instead? Just trying to figure and do my research before going to the machine shop.
Thanks, Paul

 

[Murphdog]

Typically, clearance is built into the piston. I'm sure the Icon is no different 4.312 + .038 = 4.350 bore. 440 Chrysler +.030 rings or 4.250 BBC + .100, either way, same difference, You could verify this by calling Icon, IF you can get anyone on the phone! I have a customers set at the shop. Will report back in the morning
Jeff

 

[Gliderider06]

I was able to go to the icon website and they had the instructions on the pistons. I think I'm doing the math wrong in my head, but is final bore size about .040" for the .038 pistons?

 

[Murphdog]

You need to verify piston size at suggested measuring point. Normally at piston pin center line. Then add clearance per the chart you posted. That is your finished bore size.
Jeff

 

[Murphdog]

Just measured some new IC959 pistons .078 oversize. Block 4.312 + .078 = 4.390 These are measuring 4.3845 at pin center line or .0055 clearance
at a true .078 overbore.
Jeff`

 

[Gliderider06]

Just measured some new IC959 pistons .078 oversize. Block 4.312 + .078 = 4.390 These are measuring 4.3845 at pin center line or .0055 clearance
at a true .078 overbore.
Jeff`

So, I guess I should shop for the .040 pistons from Ross then. I may have too much piston to wall clearance then by the time it has the final hone.
Thank you!
Paul

 

[Murphdog]

If your block measures 4.350 now without honing (+.038) I would say your screwed for being able to use the .038 Icom piston. .002 to finish hone for a ".040" over piston is marginal. Normally you want to leave .003 to hone at a minimum. I believe Tech Line is supposed to be able to "build up" a piston skirt with their coating so as to tighten up the clearance. I have never used it.
Jeff

 

[Gliderider06]

If your block measures 4.350 now without honing (+.038) I would say your screwed for being able to use the .038 Icom piston. .002 to finish hone for a ".040" over piston is marginal. Normally you want to leave .003 to hone at a minimum. I believe Tech Line is supposed to be able to "build up" a piston skirt with their coating so as to tighten up the clearance. I have never used it.
Jeff

Kinda what I think. I bought the block already bored. I think I will just take it to a machine shop and ask him. I had it at a shop for several months and the guy was afraid to work on it because he never worked on a W engine and didn't want to mess it up.
If I want to use the Icons, .048" or larger is what I will have to use and have it rebored.
Thank you