Overhaul questions

[Morris]

I had a fun and busy day. I pulled the head and removed the pistons on my '79. They cylinder walls looked and felt good, but there was slop in number 2. I stuck number1 piston in number 2 cylinder and no slop. Rod bearings looked okay except for number 2 which was down to copper and pitted. The middle main bearing was down to copper, too. There was a slight ridge on the crank where the oil groove is.

So what do I do next? I am on an extremely tight budget and I do not have access to a bore gauge other than my vernier calipers. The pistons came out with ease and there is almost no perceivable ridge at the cylinder tops. I really don't want to got to the machine shop unless I absolutely have to. Whatta you guys think?

When ordering parts, is there ever a time when it is appropriate to order over size bearings pistons without a bore or regrind?

The bearings are all marked with 010 above another longer number. Do you think this means that they are .010" over?

I really want to buy flat top 9:1 pistons. Do you think I will be really asking for it if I don't go ahead and regrind the crank and bore the block?

Thanks for your advice,

Morris

 

[Dave Russell]

[ QUOTE ]
but there was slop in number 2. I stuck number1 piston in number 2 cylinder and no slop. Rod bearings looked okay except for number 2 which was down to copper and pitted. The middle main bearing was down to copper, too. There was a slight ridge on the crank where the oil groove is.

So what do I do next? ---- I really don't want to got to the machine shop unless I absolutely have to. ------
When ordering parts, is there ever a time when it is appropriate to order over size bearings pistons without a bore or regrind?
The bearings are all marked with 010 above another longer number. Do you think this means that they are .010" over?
I really want to buy flat top 9:1 pistons. Do you think I will be really asking for it if I don't go ahead and regrind the crank and bore the block?
Thanks for your advice,
Morris

[/ QUOTE ]
Hi Morris,
You can't really tell what is needed without very precise measuring of cylinder bores & their diameters, for size, roundness, & taper. Likewise with the crankshaft journals. You need to at least have a machinist, with the correct measuring equipment, do some measuring. It shouldn't cost much to have the condition of these parts evaluated. Then make the decisions. Anything less will be a total crap shoot.

A good rebuild would very precisely match the cylinder bores to the new pistons, & assure that the bores are round, correct size, & not tapered & have the correct surface finish. It would assure that the crankshaft journals are round, not tapered, fit the new bearings correctly, & have the correct surface finish. Condition of the oil pump, valves, cam, should all be evaluated & corrected if necessary. There is really no other way to get a good performing engine with reasonably long life expectency.

You could possibly just replace the bearings with new .010 undersize & rings with the closest size to the bore measurments. Making sure that the ring end gaps are correct.

Doing the latter procedure could result in 35% less power & 70% less engine life. I certainly would not raise the compression ratio unless the rest of the engine was in perfect condition. It's a decision that you will have to make. Not so easy, I know.
D

 

[Bugeye58]

Sage advice, Morris. I can just about guarantee that you will be throwing money away if you install new parts without making sure that all tolerances and dimensions are within spec.
Jeff