urgent help in building up my motor

[techghost]

Ok! so to start with, i ordered crower 272/272 cams, BC springs and TI Retainers MLS with ARP for my 6 bolt 1g 4g63t.

I opened my motor and parted its head. Just incase i also checked the piston play and to my surprise all the pistons in my block had side-to-side play
this was not expected and compression of my engine was 150psi on all four.

So i'm stumped on who to proceed now and need help from you in order to determine if i need to rebore my block or keep it like that or order piston/rods/rebuild it?

how do i know if i need stock bore pistons or 0.20" or 0.4" or what?

can i just put in new rings and call it a day without changing pistons?

as mentioned i'm stumped. please help

Regards,

 

[razrman8]

If it were I, I would rebuild it. Pistons, rods, etc. If I was that far and had the chance that's what I would do. You'd be sure as to what your motor can handle. Throw in a good head gasket and you'd be set. That's just my opinion.

 

[Colt4G63 also]

Gosh, I don't know, but I sure like that roof.

I don't have the spec. in front of me, but some piston to wall clearance is normal.

If you have too much, all you can do is bore it out and buy oversize pistons.

 

[viperlp01]

You pistons are supposed to have some side to side play. There is a thing called pistons to wall clearance(PTW) which allows for piston expansion during high heat cycles. Stock PTW clearance is somewhere between .0015 to .0020. Most forged piston engines require a higher PTW. Wiseco calls for around .0035, Mahle has a different alloy than most piston companies and requires a tighter PTW right around .025(these numbers are for our size bore(85mm=3.34 inches)). ex./ Piston manufacturers will tell you .0005 per inch of bore. If your compression test showed solid numbers and they all had pretty close to the same number your perfectly ok.

Sorry for going off on a tangent.

 

[techghost]

thanks for your replies.

the piston play is not much but its there.

I can move it a little (very little feeling that it can move) holding it with my thumb (one at 3 O'clock and other at 9 O'Clock) and it moves. Similarly when i hold it again (with one thumb at 0 O'Clock and other thumb and 6 O'Clock) it moves as well.

Is this normal?

What should be the top ring gap when installed in the cylinder all alone?

 

[viperlp01]

Sorry I messed up and started talking about rings .. I edited the post. Top ring gap and bottom ring gap are very much the same as figuring out PTW clearance. But im not going to clutter up this post with ring end gap since there is no way to check it with the pistons install. You can't really check the PTW either. If you had a bore gauge to see how big your cylinder actually is you can take a close guess. They build the PTW clearance into the piston. So the piston is slightly smaller than the bore. So if your bore is still right on 85mm than your good.

Everything that your telling us is normal.

 

[techghost]

i can take one piston/rod apart and test out the wall clearance or ring clearance. will do that tomorrow.

Meanwhile can please let me know the stock ring clearance etc?

 

[viperlp01]

Stock ring end gap is up to you. I usually build engines to .018 on the top ring and .020 on the bottom regardless of engine being built unless the specify a custom order. That's a safe number to use.

 

[techghost]

is there a video where i can see normal play of pistons?

I can move it a little (very little feeling that it can move) holding it with my thumb (one at 3 O'clock and other at 9 O'Clock) and it moves. Similarly when i hold it again (with one thumb at 0 O'Clock and other thumb and 6 O'Clock) it moves as well.

Can anyone confirm this to me please, Is this normal? i need to get it confirmed from as many friends as possible or i should keep this confusion out of my mind.

 

[Tyeler18]

Mine did the same thing in both talons. They move less than a mm? I couldn't really see my move, but you can feel it. No big deal.

 

[techghost]

i cant see them moving either but i can feel them moving when i push the with my thumb at different ends.

 

[Tyeler18]

That's basically how mine was too. Motor checked out fine.

 

[LVDSMKING]

I would try to pick up a feeler gauge set and check it that way it the only way to be sure but if you cant see them move then it probably not a serious issue

 

[techghost]

how can i check the bore size? is it possible to check it with a vernier caliper?
what should be the size of a piston?

@LVDSMKING

how can i check it with a feeler gauge? can you please explain!

 

[viperlp01]

I don't understand why you are still asking questions. What do you expect the pistons to be a PERFECT fit with no play. You wouldn't need piston rings if the piston was that tight in the cylinder. TRUST ME, the movement of the piston is completely normal. If the PTW was too big(which there is no way) you would notice crazy piston slap at initial start up until the piston warmed and expanded. You need a bore gauge to check the bore and it is just pointless to buy one. Put the car back together already.

I would try to pick up a feeler gauge set and check it that way it the only way to be sure but if you cant see them move then it probably not a serious issue

You can't use a feeler gauge to get this. You use a caliper to check the width of the piston and then a bore gauge to check the bore size.