Ok so I got a set of forged pistons ,8.8:1 std bore. So when I compare them to my stock ones they are like 1/16 smaller in dia....whats the deal there? Did they get me the wrong pistons? Also they are coated with some sort of 'powder coat' on the top of the piston (grey looking). Then after the last ring land they are coated with a really smooth surface. Is this pretty normal? Other than the dia of the piston itself it looks like a regular 'dish' piston. All of the other things on it look exactly like a stock piston. The oil holes are in the exact same spots as the stocker and the wrist pin is the same.
My first thought was he got me the 4g63 pistons by mistake? Could this be the case? I called a shop near hear but I don't trust them. They said that is normal and the rings would make up for that difference. I am really skeptcal here.
I have already done two rebuilds, but with stock pistons. These just don't look right to me. If the dia of them was the same I would not have a problem with them, but.......1/16 of an inch seems to be alot to me.
Please no flames about using 'stock' bore pistons. On the last rebuild everything checked out fine. My dad used a Micrometer thing and all the cyl were good. And my compression is really consistant. 181-184 across the board

Kevin
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k from what i understand, forged pistons expand more than our stock ones and that's why they're slightly smaller. if you could compare it when they're hot it wouldn't be. before your car warms up you'll get a lotta piston slap an stuff too. and the coating you're talking about is ceramic coating or something, i believe. it helps disipate heat. i've never done rebuild or anything though so i'm just going from what i've learned on the board. someone correct me if i'm wrong

-marc

='95 RS 5spd Red=
Matrix TypeX CAI
A'pexi Turbo N1
Nakayama GT5 17's
Ractive STB
GSX Calipers
AEM 12.5" X-Drilled/Slotted Rotors

255 is fricken short

that is what im thinking too, I just want to be sure before i drop these guys in there next monday.

Kevin
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The new:

Give Moto the old ringer...

the other hawaii guy is right it does expand more causing the piston to get all snug but you will have some piston slap when you warm up your car

if you want someone told me to put my forged pistons in a toaster oven for a couple mins to set it right before i installed but i never did and my install came out good

hawaii boy

Same here.

After the initial "KICK ASS! WE DID IT!" and all the attaboys that come with starting her up after rebuild, you will get nervous about the way they sound. Mine sounds like a Cummins when I first start it up in the AM. After it warms up, it still sounds different, but different good.

Well tonight I found out they were for the 4G63. So my suspicions were right on the size. They just looked too small in dia. He has the right set comming. Rebuild starts on Sunday! Im totally stoked. Finally I can up the boost to 8-9lbs . (after the proper break in period of course)

Kevin
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The new: