Engine clearances

[BS]

Gordon,

When you guys assemble an engine, what bearing clearances do you shoot for? If the service manual calls for .0007-.0024" clearances, does a clearance of .0026 make enough difference to worry about?
Do you use the piston and ring manufacturer clearance spec's for gospel or do you have a tendency to go one way or another depending on your experience with each manufacturer's product and the use it will be put to?
Do you use a torque plate to make your final pre-assembly measurements? How important is it to use the torque plate?
I guess in the past I've always trusted my engine machinist to do the job right and I just plugged the parts in. He was really good, so I guess I got spoiled. He has since retired and I am shopping for a good new machinist and think my buddy finally found one- at least his mic's seem to bear this out.
Just curious how you guys do it. Does every thing get measured, written down, and matched?

Thanks,
Bob

[Gordon Levy]

BS, I will try to answer this as best I can.
First, machining is cridical to how the engine performs and lives. A good machinist can make you 25hp just in proper machine work. On the engines we build, we line bore, torque plate hone to specific pistons and ring type, balance everything, and use quality pieces.
The bearing clearence depends on the engine use. Street engines get.0015 and race engines get .002-.0025. Race engines make more power running them loose but don't last a real long time.
I clearence rings depending on the use of the engine. EFI or carb, NA or blown, Street or race. All of these have different clearences. It take years of R&D to figure out which gaps are best for which application.
Always torque plate hone, this makes sure the bores are straight.
Having a good machinists is everything when building and engine. It took me a while to fine the one that I currently use and he has never let me down.

[brent5]

Go to speedomotive website and looh for engine building tips.lots of good stuff there.