I just can't seem to get rid of this thing. I sold this thing once already, previous owner just GAVE it back to me. It has a few thousand miles on it since the original owner had built it.

Anyway when I got it, it had sat for quiet some time. The motor was locked up and took a 4 foot bar plus all my muscle to set free. I saw the heads were covered in surface rust and the valves all had bubbled when I sprayed WD40 on them. At this point I had sold it when I saw the poor compression it made... something like 30-60 PSI in every cylinder.

Upon getting it back I took the heads off. I had the heads cleaned up, ported, rebuilt and pressure tested at 140? psi each. Originally they had tested at 40-60psi each.

The bore is something like .042-.043 over (checked it with both mics) but the cylinder walls are perfectly smooth. The pistons all have a tiny bit of play left to right in the cylinders, it's not much at all. I have never pulled apart a rotating assembly and am a bit intimidated. The oil is spotless, the pump filter and pan have zero metal shavings.
the pushrods all appear to be straight as well.

If the valves were seized closed; could that explain why the motor was locked up originally? The entire rotating assembly spins incredibly easy now that it's unseized and the heads are off.


anyway to tell if the rings or crank bearings are bad without pulling it all out? what are my chances that it was just the heads causing all the problems? I'd hate to get the heads back on to find out it makes terrible compression still.

 

Little update, I grew a set and pulled it apart.
So far I checked 3 mains; crank and bearings appear perfect. All rod bearings appear perfect too. I only pulled one piston out so far and the rings are intact. I will have to measure tolerances of it tomorrow. I think I'm just going to go ahead and hone it and get moly rings.

 

Send it to a machine shop and have them rebuild it properly.

 

What would cause one of the ears on a piston to snap? All the bearings are good, I think the chunk of the piston was hanging up in the crank. Their is no damage anywhere from the bad piston either.

 

What size are the pistons?
What type of pistons are they, material?
How much clearance is there supposed to be between the piston and the wall?

Different types of pistons require different clearances. Forged pistons require more clearance because they expand more when the heat up.

All pistons will rock on the wrist pin.

 

One of the sleeves of the piston was blown apart, they are stamped B551. I can't find the same type of piston so I'm jusy buying a new set.