more engine machining questions???

[Dan]

alot of talk around here lately about getting machine work done so it sounds like a good time to ask a few questions I have...
-what are the bare minimum, essential process' I need done for a healthy street motor (assuming bore and crank are within specs, what other things do I HAVE to have done)??
-to clean threaded holes I can just run the proper size tap through them? any tap? Is there a chart that tells me what size tap to use to clean a specific hole??
Thanks-

[Digger_Dave]

[ QUOTE ]
---to clean threaded holes I can just run the proper size tap through them? any tap? Is there a chart that tells me what size tap to use to clean a specific hole??
Thanks-

[/ QUOTE ]

When your cleaning up threads you should use what are often refered to as "Thread Chasing Taps or Dies." The chase taps and dies are identified by the same sizes as the threaded hole or bolt your trying to clean up.

If you use regular taps and dies you can cut the thread a bit over sized which weakens the fastener and makes it "sloppy."

[Dan]

Dave-that was exactly what I needed to know, I have cleaned some threads in the past with regular taps and they never felt quite right afterwords, thanks for straightening me out-

[squirrel]

[ QUOTE ]
-what are the bare minimum, essential process' I need done for a healthy street motor (assuming bore and crank are within specs, what other things do I HAVE to have done)??

[/ QUOTE ]

The bare minimum you need to get done depends on how long you want it to live. I'd suggest getting the rod big ends checked, and resized if needed (with new bolts), replace the cam bearings and all soft plugs, polish the crank, replace the pistons and hone for proper clearance (but most blocks need to be bored also because of excessive clearance). As long as the main caps fit tight and the crank turns free you shouldn't need a line bore/hone. If the deck surfaces are rough you should deck the block, but many blocks are ok without this work. Balancing is a good idea if you change piston type, you can get away without it on a stock rebuild.

On the heads most need guides redone, and new valvesprings, along with a valve job. Many heads need to be resurfaced (milled, not sanded!). Early heads (pre 1975) should have hardened seats installed unless you will never load it down (heavy car with highway gears) or you don't plan on putting more than 20k miles on it.

I've done cheapy overhauls with just a hone job, new bearings, new or reground cam and new lifters, and valve job, and got 20k miles or more out of it. It depends on how bad it was to start with--the more taper there is in the cylinders, the quicker rings will wear out.