360 piston wall help

[tguss]

I picked up a 360 block and crank dispose to be 30 over bore is the piston hole should it be 4.030 when measureing it ? Also is the walls bad it have lines running in it , I can't feel them hand not groves in walls

 

[tguss]

Sorry for bad spelling ,,, spell check

 

[Rotax]

final size will depend on piston size and running clearance. Say your piston is 4.030.and clearance is 11/2 thousands . bore should be 4.0315. This is fresh not used yours could be bigger from wear.

 

[Locomotion]

Engine builder or whoever is going to hone the block should measure the pistons and then see if the bore will clean-up with a light hone. I believe some if not all pistons would be smaller than the bore size. But you just have to check what you have against the pistons used and the manufacturer clearance recommendations. Clearance varies based on piston material and intended use.

The "lines" are just normal wear marks. A light hone would be good, if clearances would still be within spec. Honing with a honing plate and type of gasket to be used in final assembly will provide the roundest bores, best ring seal and longest life. But that's usually best to do while boring to the next oversize. Using a plate with just a light hone (if it wasn't done that way before) may leave some low spots.

The reason for a plate is to simulate bore distortion caused when the heads are bolted on. That way, honing with plates makes rounder bores. Unbolt the plates and measure and you can find some out-of-roundness. But when you bolt the heads on, it goes back to the roundness achieved with the plate honing.

 

[tguss]

Ok thanks , you all helped alot