How to check if 6 bolt bore and pistons are good?

[Wanagofast]

I have JE pistons that came out of the engine. 3/4 were in good condition and the other piston was scuffed up and the shop told me to get a new one. So here's my question. How do i check to see if i can just drop a new piston in to replace it? The forging number on the piston is 85m. I believe its part number is 208478 but I'm not 100% sure the shop measured 3.359 as the diameter. I really need help any imfo will help

 

[brandonpurnell]

Wouldn't you have to buy a whole new set? Im not sure im just wondering.

 

[nitrouskris]

post some pics

 

[genegoesfast]

Is the bore in good shape? Measure it with a bore scope and check for scoring.

 

[Wanagofast]

I have lines on the walls where the pistons sat. But the bores arn't egged shaped and seem equal, no scraps whatsoever. My hopes are to get it align honed and get the new piston and rings. I will post pics tomorrow.

And the shop said they recommend a new set but also said i'd be fine getting with just a replacement as well.

 

[genegoesfast]

I have lines on the walls where the pistons sat. But the bores arn't egged shaped and seem equal, no scraps whatsoever. My hopes are to get it align honed and get the new piston and rings. I will post pics tomorrow.

And the shop said they recommend a new set but also said i'd be fine getting with just a replacement as well.

You don't need to eyeball it. Measure it. Measure it again. You need to measure at several different points in the cylinder with a bore gauge. If you can feel anything in the cylinder wall with your fingernail it might need more than a hone. Align hone is for crank and cam bores, not cylinder walls.

 

[Wanagofast]

i checked with a cylinders with a bore telescoping gauge and they seemed all equal but i wanted some input before i continued. The engine was rebuilt about 1,800 miles ago the guy before me seized the crank (main reason for build) and I'm just trying to make sure i don't screw up like he did. And probably a good thing you told me about that hone. Cause the machine shop would probably get a good laugh at that.

 

[arrowhead]

More than likely you will need to rebore and get new pistons if you have all those grooves, you say you only need one piston but I dont think you really know. and the price you would pay for only one, it is not worth it probably.

Leave the measurements to your machine shop and dont play machinist, there is a lot more to what you are trying to do than just use a bore scope.

 

[pearl4gtsi]

I second his motion ^.... Just get a whole new set of pistons, larger of course, I would assume .020 over and have a machine shop re-bore it. That is the safest route with a much better chance for the longevity of the motor.

Sure, you might be able to get away with just the one.... But do you want to do this again in another 1800 miles?!?

And if the guy before you seized the crank..... If you decide to bring it to a machine shop, have them look the whole block over, just for peace of mind.

 

[BogusSVO]

I have JE pistons that came out of the engine. 3/4 were in good condition and the other piston was scuffed up and the shop told me to get a new one. So here's my question. How do i check to see if i can just drop a new piston in to replace it? The forging number on the piston is 85m. I believe its part number is 208478 but I'm not 100% sure the shop measured 3.359 as the diameter. I really need help any imfo will help

Looks like you are .020 at this point.

STD bore is 85mm = 3.346

A .50mm over would be 3.366

Subtract .0035 for PTW the piston should mic out 3.3625-3.363

With you having a piston mic'ed at 3.359, it reads to me you have a collapsed piston by about .004

Yes you can get one piston to complete the set, assuming you had the other 3 pistons mic'ed and they are in spec.

But you will have to weight match all 4 pistons to the lightest one

Now depending on what your cylinder bores mic out, you may be ok to hone and go.

If not you have a choice, get another set of pistons, or get another block and bore to the pistons you have.

If you have ARP main studs, have the main bores checked, and align hone as needed.