Max overbore on AMC 360?

[FullSizeJeeper]

I've got an 74' AMC 360 engine at .040 over currently. I was doing some head mods and decided to pull the lower end to take a look. Overheated at some point and have some piston damage and mild scoring on two cylinders. Considering boring to .050 or .060 over. This is a offroad/torgue engine for a FSJ Cherokee, never over 5000RPMs, DD, that I'm hoping to get 350+ ftlbs of torque and 250+hp out of.

Is there a set of Cast pistons out there at .050 over for AMC? I can get .060 over from Bulltear.
What concerns are there with cooling and thin walls in the early model AMC blocks when over bored that large?

The block is at the shop getting tanked now, I'll get an accurate, current bore size soon. Might consider a good hone to clean up and use .040 over pistons. How much tolerance between pistion and bore size can you get away with?

[AMX69PHATTY]

FACTORY SPECS ON A NEW MOTOR IS .001-.002 CLEARANCE ON DIMAETER FOR CAST PISTONS.
FOR FORGED PISTONS CLEARANCE IS .006-.009 ON DIAMETER.
THE THING IS THE HOLES GET OUT OF ROUND AND MUSHROOMED.
IF YOUR NOT LOOKING FOR 100,000 MOTOR, .004+ WILL STILL RUN,
JUST MAY USE A LITTLE OIL, HAVE SOME BLOW BY, DON'T THINK PISTONS WOULD SLAP.
LOOSE MOTORS RUN BETTER :mrgreen:
AMC BLOCKS HAVE HIGH NICKEL CONTENT AND ARE PRETTY HARD.
I DON'T ALWAYS TRUST SHOPS, FOR THEM IT'S BEST TO BORE IT OUT,
BE SURE IT'S TRUE AND TO SIZE, AND MAKE THE MARGIN ON THE MACHINE WORK AND NEW PISTONS.
SOMEONE HERE WAS SAYING YOU CAN USE MURIATIC ACID TO REMOVE ALUMINUM FROM THE BORES.
JUST A MATTER OF HOW FAR ONE WANTS TO GO.
COULD JUST HONE IT AND RE-RING IT, WON'T BE ANY WORSE THAN IT WAS.
OTHERS HERE HAVE MORE HANDS ON AND KNOW MORE THAN I.
SOMETHING WIERD THATS CAME ABOUT, NEW ROD BEARINGS ARE NOW MADE
WITHOUT THE NOTCH THAT FEEDS THE CON ROD OIL SQUIRT HOLE.
DIFFERING OPINIONS ON IF THEY ARE NECCASARY OR NOT.
ONE WOULD HAVE TO NOTCH THE NEW ROD BEARINGS THEMSELF.

THERE'S A GUY IN THIS FORUM, HOLESHOT, HE MAY KNOW A SOURCE FOR +.050 PISTONS.
HAVE YOU TRIED FAST ENGINE PARTS.COM aka MADDOG RACING ?
SOME HERE DON'T CARE FOR THEM, BUT THEY HAVE AMC STUFF AT GOOD PRICES.

[jeepsr4ever]

Thats pretty early and I would sonic test it to see where the thinnest spot is. Anything under .1 can be pushing it for a wall thickness. I do know several of the early year AMC 360's (71-82) had VERY thick walls

[FullSizeJeeper]

AMX69PHATTY,
Thanks for the info, I read the thread on the piston wear after 300 miles. I noticed a similar pattern of wear between cylinders (number 5 and 7 were worst, one side not as bad as the other. But mine is definetly an overheat.
I know the machinest. I'll go by with a six pack after he cleans it up and we'll take a good look and measure and make a plan. Just want to know what options are viable and reasonably priced. I'll give Maddog a look. I've seen them on E-bay, haven't used them yet.

jeepsr4ever,
The main concern being cooling on walls under .1? This is a preety thick block, but if I can get by with a good hone and new ring, I'd rather save those .01 or .02 of block for the future!