Unusual bore wear on 62 Scout 152 engine?

B

BigSliv

New member
Hi.

I am restoring a a 62 Scout 80 with my 14 year old daughter as an opportunity to teach her some mechanical skills and hopefully provide her with wheels by time she is ready to drive. We are into the engine now and I am currently in uncertain waters as I have never rebuilt an engine before.

I expected cylinder wear perpendicular to the crank to be worse than the front-to-back wear but when I took measurements on the 4 bores (using a bore-guage), I found that the wear parallel to the crank was about 50% worse than the perpendicular wear.

Is that normal?

Is that an indication that some other part tolerances are out of spec?


Also, is there a rule of thumb for determining how much over a cylinder should be bored given the worst wear measurement? My worst was +.0160" below the ridge on the #1 cylinder parallel to crank (perpendicular was +.0095). Note: those measurements are relative to the nominal bore diameter of 3.875". Btw, measurements on all bore locations other than below the ridge, were typically between .001" - .002".
 
Very hard to say for certain why you have the a symmetrical wear. I would not worry about it much. That much wear and such a large ridge indicates it was ingesting large amounts of particulate through the intake...

While the machine shop will need to determine how big they will need to go it would seem that .030 would be a minimum. They need to guarantee the initial boring operation cleans it up and they will want to leave say .005 to finish hone and size. Some shops are better then others but the preceding is a general rule.
You've got plenty of barrel thickness so even if you need to go bigger than .030 don't sweat it.
 
Thanks for the reply Robert. Regarding the heavy wear below the ridge; given the amount of oil and dirt caked on top of the engine, I suspect the po had let the oil-bath air filter go dry resulting in little or no filtration.
 
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