Inspecting an engine I bought.New Mega block 4.32 bore Ross pistons
.0055/.006 skirt clearance.
Engine has been sitting probably 10 years. Turns freely.
Anyway.pulled piston to check clearances and found this:
Pan is squeeky clean. Bore measures good all the way down,no burr at the bottom,wrist pin free.
Has about 1,000 street miles,low compression small hyd.cam.

It looks like either tight at bottom,is not.
Burr on edge,,no
Tight wrist pin,no.

Bore measures good all the way down,no burr at the bottom,wrist pin free.

Is that measured as in the pics or with a tq plate bolted on?

Could just of been a dirty assembly?

Cam looks like more then 1k miles, possibly.

Cough,cough....

Your point?
Piston tops are loaded with gray soft ash,must have been running race gas in a 9to1 street car.crazy

Where the rings file to fit? If so did you deburr the outer edge,ends, thoroughly?
There is always a reason for parts failures and witness marks from that failure this motor is talking to you and us
Now comes the hard part, figuring out exactly what it is saying

Didn't Ross have bad run of pistons that expanded more than they were spec'd to? I have a set in my 493 that look like that. Built in 2005ish.

Kevin

Hmmmm that's exactly what I thought when I saw it,not enough clearance. But measures ok.
Can't have many miles, has new stamped rockers and the black coating isn't fully polished off on the valve contact.

I didn't build it bought it this way CHEAP. Block this worth more than I paid for the whole running 487cu stroker.

Hmmmm that's exactly what I thought when I saw it,not enough clearance. But measures ok.
Can't have many miles, has new stamped rockers and the black coating isn't fully polished off on the valve contact.

I didn't build it bought it this way CHEAP. Block this worth more than I paid for the whole running 487cu stroker.

You can wipe the gray soot off the pistons with your fingers.
Gritty like gray toothpaste.
I wonder if it ran so rich ,or flooded the carb.(repeatedly ) and washed down the cylinders, and the soot got past the rings with it.

I don't think it looks that bad.

That is caused by piston skirt profile. I would imagine that Ross has changed their profile by now.

Only the one cylinder shown, or all of them?

The "If it were mine" thought is: tear it down, see if the cylinders can be cleaned up with a rehone, and have the pustons skirts coated if you want/need to reduce the clearance. Or bite the bullet and take it to tbe next oversize required to make it right.

This a good example of why I don't trust machine work or assembly procdures beyond than the small number of shops I deal with.

Only had one out so far.
Regardless ,,it will get rigid honed and re-ringed.

Wanted to open ring gaps anyway. Might throw some boost to it down the road.

Ross has used tbe same skirt design for their stocking BBM pistons for 20 years, right or wrong.

I'm interested in hearing if the OP says this was found on every cylinder, or isolated to the one he posted photos.

All 8 show scuffing #1 in the 1st post by far the worst.
All scuffing in line with the wrist pin.

What would be the result of wide open/RPM with a stone cold engine??
The pistons would expand way faster than the thick block???
Just thinking ...Why?

Bore measures 4.321
Piston 4.3155

I'm sure hes pointing out all the white specs. A classic indicator of detonation. Pics can be deceiving though.

Maybe so,, perhaps he works for CNN.? LOL

I agree alot with what BradH posted. Id hone it, coat the skirts,ect.

I also agree with the thought of maybe it being abused before up to proper temp.

In the above pic, look how much got past the first ring,(center piston).

From my own personal small errors in my younger days to me overall it looks like some good quality parts but just maybe several minor things done wrong, went wrong, adjusted wrong.


My comment on the pics were the buildup, the color and the amount for being a 1k mile motor that looked to be way out of tune.

I think you could have a killer build still without breaking the bank.

Hope so.
Tore it down to a bare block today.
It was built by Muscle Motors-stamped on the crank. Eagle and Ross parts,Mega Block.
Freshen it up and on the the next steps.

Thanks for all the suggestions.

https://www.youtube.com/watch?v=6uK7i4NHuEA

Helpful video but it's pretty obvious you know all this already. It definitely seems to line up with being too tight even though they're measuring okay.