piston to cyl clearance

[mopar1970]

I am rebuilding a 2cyl 60 hp and the machinest says i can just hone but i will be .003 over stock bore size which will put me at about .006 cyl to bore clearance is this acceptable or should i just bore? How long will the motor last and and what is the disadvantages I am buying new pitons anayway. I will be using forged pistons.
thanks,
chris

 

[Dhadley]

Re: piston to cyl clearance

Not sure which 60 hp you have but normal wear tolerances on an OMC is .004". So if you'll be at .003" after honing, you'll have about 1/4 of the life left in the motor compared to a new or fresh bored cylinder. That will still give you lots of running hours but something to consider.

Now, the biggest expense of boring is buying new pistons. You're going to buy pistons anyway so that's not a factor.

Honing a cylinder at a machine shop is, on average, about $10-$15 per cylinder. Boring is about $35-$40. Boring prices include finish honing and deburring. Once you do the math, for a tiny bit of $ you gain back that other 75% of engine life.

 

[mopar1970]

Re: piston to cyl clearance

Thats what I was thinking But the mahinist said it would be fine. From what I have seen the machine shop that has my block is overpriced they want $40 to hone the block and $60 a cyl to bore and hone. I am thinking of going elsewhwere. I have seen prices on the internet for $39 a cyl to bore and hone the very block that I have.
I was thinking along your lines too that I am already buying pistons since the onld ones were worn out they measured abou .013 piston to cyl clearence with the old ones.
Thanks,
Chris

 

[Dhadley]

Re: piston to cyl clearance

The newest version of that piston is cam ground and barrel shaped. They're all tapered so it's pretty hard to measure one but you should be fine.

If you're looking for another machine shop I'd recommend Mar-Fab in Tenn. They do great work and can supply anything you need to rebuild the motor. If you go that direction, emil me and I'll get their contact info for you.