Piston to bore problem...please help

[TSIfreek]

Matt did you bring the block and pistons to your machineist?? Did he measure the bores and pistons?? Yes you need more clearance for the forged pistons but how much you have we cant tell just from the pictures. If you do not have any measurements on the block I would dissasemble it and bring in the bare block and the pistons and rings to a machineist to check the clearances of each bore and each piston and match them up. BTW did the block get decked?? Doesnt look that clean. Sorry if its not what you wanted to hear but its what I would do.

 

[1fast97gsx]

yea what exactly was done to that block? As far as the clearances ... even the smartest person in the world couldn't tell you from a picture. You have to physically meassure the pistons and the bores. The proper way to set clearances is the number the pistons 1-4 and then finish the bores accordingly so all the clearances are correct.

 

[blackGSX2g]

Matt did you bring the block and pistons to your machineist?? Did he measure the bores and pistons?? Yes you need more clearance for the forged pistons but how much you have we cant tell just from the pictures. If you do not have any measurements on the block I would dissasemble it and bring in the bare block and the pistons and rings to a machineist to check the clearances of each bore and each piston and match them up. BTW did the block get decked?? Doesnt look that clean. Sorry if its not what you wanted to hear but its what I would do.

It was not decked at the time of the picture (last week), but I had that and my new head resurfaced when I took it all apart again. I brought the pistons to my machinist and he said the clearences were fine, he usually sets Weisco's at .003 and there were closer to .004. I just wanted to update with pics as my camera has been sitting there since the day I took the pic, and I wanted to quadruple check...sorry, I just worry about everything.

 

[anconover]

So he said 'the clearances are fine'? I wouldnt take that as an acceptable answer. He usually sets them to .003 (per wiseco spec) but these were closer to .004? How close? Id ask an exact measurement. .003 and .004 is quite a large difference when it comes down to it IMO.

 

[Brian Nutter]

Hi there, short note here. All pistons are tapered from top to bottom. The bottom of this piston will measure about .003-.004 clearance, but the top to the top ring land will have about .0026-.035 clearance to the bore as the top of the piston is taking the majority of the heat. Under running conditions, this tightens up to where the land is *almost* touching the bore. So yes, the piston will rock in a cold static measurement. Never check piston to wall clearance with a feeler guage. It's about worthless. A micrometer to measure the piston and a dial bore guage set off the micrometer goes in the bore to show a net clearance to the piston. Have fun with the car!--Brian Nutter-Wiseco Piston Co.

 

[Maglin]

I would think if you are planing on running high boost 25+ PSI with a big turbo then you would actually want to go .004" for your piston to cyl. wall clearance. Cause you are really going to be heating those pistons up and it will allow for the extra growth due to said heat.

I'm going to be running .004" with my 9:1 wiseco's, but I do plan on running 30 PSI with a HX-35 pushing 500+ WHP...

 

[Brian Nutter]

Yes, mostly it depends on whether the engine is going to get a 500 mile break in or not. The forging design we use with Mitsubishi's is very forgiving. If we do go with a break in, even w/ 25 lbs, the .003 is fine as our standard skirt coatings are about .0005 thick and really make for a happy cylinder/piston relationship. I'm ok w/ .004 if you're going straight to the track, but even our track-only 850-1000hp customers are only running .004-.005" clearance. .0055-.006 is basically double our original recommended clearance and it will certainly put a beating on the skirts, cause noise, and possibly crack or collapse the skirts. Every case is different and has to be approached as such. Thanks, Brian Nutter-Wiseco piston

 

[Maglin]

Yes, mostly it depends on whether the engine is going to get a 500 mile break in or not. The forging design we use with Mitsubishi's is very forgiving. If we do go with a break in, even w/ 25 lbs, the .003 is fine as our standard skirt coatings are about .0005 thick and really make for a happy cylinder/piston relationship. I'm ok w/ .004 if you're going straight to the track, but even our track-only 850-1000hp customers are only running .004-.005" clearance. .0055-.006 is basically double our original recommended clearance and it will certainly put a beating on the skirts, cause noise, and possibly crack or collapse the skirts. Every case is different and has to be approached as such. Thanks, Brian Nutter-Wiseco piston

ahhh... Thank you for the extra info... Maybe I'll go .0035 instead... I'm mainly a DD with track use about 2-3 times a month...