piston to wall

5thgen · Post by **5thgen** » Mon Jul 27, 2009 2:26 am

what clearance are you rebuilt / built guys running?

RyanA · Post by **RyanA** » Wed Jul 29, 2009 12:33 pm

Well, on the engines I have built, I have run anywhere from .001 to about .005.

Hope that answers your question. Good luck.

5thgen · Post by **5thgen** » Wed Jul 29, 2009 6:40 pm

RyanA;191083 wrote:Well, on the engines I have built, I have run anywhere from .001 to about .005.

Hope that answers your question. Good luck.

Right now I've got anywhere from .0034 - .0039 measuring the shortest point of the cylinder. I asked for .0040 - .0045 and the smaller cylinders are concerning me.

Have you ever had any issues with out of round or tapered cylinders? I've got some that are up to 5 ten thousandths off in some places....which isn't a lot....I believe service limits are .002, but it concerns me a little.

I also have out of round measurements on the mains. Vertical measurements come close to what I need....but everything else fluctuates around, usually growing on the sides ( More visible with the bearings in and caps torqued down ) .

RyanA · Post by **RyanA** » Thu Jul 30, 2009 6:01 am

That kind of sucks. You just using stock bore or has the block been bored? If it's stock, I'd say you need to bore it. If it's bored, well, that may not be good. I would not exceed service limits for any out of round spec. If you want a good, long running engine, the cylinders and the bearing bores both need to be as close to perfect as possible.

5thgen · Post by **5thgen** » Thu Jul 30, 2009 8:49 am

RyanA;191167 wrote:That kind of sucks. You just using stock bore or has the block been bored? If it's stock, I'd say you need to bore it. If it's bored, well, that may not be good. I would not exceed service limits for any out of round spec. If you want a good, long running engine, the cylinders and the bearing bores both need to be as close to perfect as possible.

The bore doesn't concern me a whole lot....boring/honing should take care of that. It is a 84mm sleeved block made from a b18a1. Looking at my measurements, my worst taper is .0006 and my worst out of round is .0008. My biggest worry is my #5 main. 20 degrees off of my horizontal measurement gives me a .0002 oil clearance. And to top it off, the #5 cap also has a heat rainbow around it.

Fantastic.

RyanA · Post by **RyanA** » Thu Jul 30, 2009 11:36 am

Well, sounds like worst case you may have to throw a cap on it and line bore/hone it although a lot of people would run that cap just the way it is.