New pistons: quick question

[Subliminal]

Ken,

No go on local stores having a 'piston ring grinder'.

Do you think they are too hard to use a fine file?

[glhsken]

It can and has been done... It's touchy work.

You sure they gave you the correct ring size??

[Subliminal]

Yeah, they're standard size. I just went through some of my pm I've exchanged since I started this project, and I found out that I MIGHT have measured wrong.

I was using a factory service manual to determine the gap, however, it was a FSM from 84, and the car is an 85. The 84 book says to allow 10 thousanths, which i don't quite have. However, I was talking to someone and they told me the gap should be 8 thousanths...which might work (the 10 was just ever so slightly too big)

Any thoughts on that?

Thanks again

d

[glhsken]

8 thou is aweful tight... Stock 2.2 piston is more in the 14-16 thou range.

I'm running 22/20 on mine (top bottom) to allow for higher boost. A friend of mine is running 28/26. Having the ring gaps butt at high boost is instant piston top peel off time...

[Shelby15psi]

Quote:

Originally posted by glhsken Even with out valve reliefs, the swirl is non interference with a stock lift cam. Not by much, but it is. Valve reliefs do not make anything "better" just by their presence Dustin.

Ok. What I meant to say, instead of "Better" was maybe with the valve reliefs, it also made a difference in how the fuel burned, some pistons are designed to make combustion more effecient arent they? Anyways, So I dont hazve to worry about valves hitting pistons or anything like that do I with a 85 head?

Dustin

[Subliminal]

Dustin...no...in fact its quite the opposite. the 85 head has much more room than an 86+

d

[JandHbodies]

I was told 4 thousanths oil ring clearance for every inch of piston diameter. I know its works true for 350's, but is it the case with all cars?

[Shelby15psi]

Oh alright, so since I have the newer style pistons and the 85 head, im still ok right?



Dusty

Yup, you'll get lower compression. I was told once that the difference between the two heads was half a point of compression ratio.. ie, instead of 8.1:1, it'll be 7.6:1.. I'm sure Kenny will correct me if I was told wrong before. Less compression = more boost with the same octane fuel before detonation. A Good Thing.

[turbovanman]

I just changed my head gasket and I have stock oversize replacement pistons in my 89 and no valve reliefs, guess its up the manufacter if they do or don't put them in.

Rule of thumb is .004" for each inch of bore!!! I think mine gapped out at .016"-.019" when I built my motor. Blowby is very low so must be ok.

Valve reliefs are just that, if you run high lift cams, they give you a little extra room so the piston doesn't hit the valve!!!!

[glhsken]

Quote:

I just changed my head gasket and I have stock oversize replacement pistons in my 89 and no valve reliefs,

Then they aren't the stock pistons... Stock size yes... Production cars from 86 up HAD valvereliefs on the pistons.

[turbovanman]

Quote:

Originally posted by glhsken Then they aren't the stock pistons... Stock size yes... Production cars from 86 up HAD valvereliefs on the pistons.

Very strange!!!!!!!!!! I could be brain farting but it was only Monday when I had the head off. They are aftermarket stock cast pistons, .020" oversize.

[glhsken]

Yours could be.... but again. they are aftermarket.