cylinder pits, suggestions? Machine Shop report

AMC did factory .010 overbore and on Gen 2 engines it was denoted as a B stamped in the valve cover tag.   I would NOT recommend a Moly ring is engines that are not used frequently, they are very slow to break in after installation.

I put a 401 +.030 years ago with Moly Rings and it didn't slow the oil consumption until about 10K miles....about 1 1/2 qt every 3K miles, then used no oil. My brother ran a large automotive engine re-man (they did about 40 engines of all kinds a week)and install facility...they also saw much worse oil use issues at low mileage when installing Moly Rings....which was a big warranty issue. After consulting with several other builders, they all said to go back to straight up cast iron....especially in low use applications...like older car restorations. The break in can vary greatly with the microfinish of the cylinder bore, break in oil type and brand of ring package. So I have always moved to the safe side, lets face it MOST restorations will see little miles. I asked my friend that is Chief Designer at Keith Black Piston (United Engine) about this too and he agreed that in most applications Moly Ring has little benefits and customers complaints about Blue Smoke at idle on fresh engines is not easy to explain to folks not technical on reciprocating engines. He also said the Moly Ring Technology has change dramatically since it's introduction (for the better).   His (and mine) opinion is run a Normal Cast Iron Ring for a stock piston....in performance applications where rotating friction needs (you want) to be low, moly ring combined with a moly coated piston are great combinations. One last thing....he mentioned too, DO NOT RUN Full Synthetic Oil for at least one oil change on cast iron rings and maybe 2 on modern Moly Ring...that low friction lubricant will never allow the rings to break in. Your experience may vary...but after number 100 AMC Gen 2 engine under my belt this is what I have seen......another reason I will not patch a problem fresh built engine by another mechanic. It is a no win situation for you or the customer.

401MATCOUPE wrote: I put a 401 +.030 years ago with Moly Rings and it didn't slow the oil consumption until about 10K miles....about 1 1/2 qt every 3K miles, then used no oil. My brother ran a large automotive engine re-man (they did about 40 engines of all kinds a week)and install facility...they also saw much worse oil use issues at low mileage when installing Moly Rings....which was a big warranty issue. After consulting with several other builders, they all said to go back to straight up cast iron....especially in low use applications...like older car restorations. The break in can vary greatly with the microfinish of the cylinder bore, break in oil type and brand of ring package. So I have always moved to the safe side, lets face it MOST restorations will see little miles. I asked my friend that is Chief Designer at Keith Black Piston (United Engine) about this too and he agreed that in most applications Moly Ring has little benefits and customers complaints about Blue Smoke at idle on fresh engines is not easy to explain to folks not technical on reciprocating engines. He also said the Moly Ring Technology has change dramatically since it's introduction (for the better).   His (and mine) opinion is run a Normal Cast Iron Ring for a stock piston....in performance applications where rotating friction needs (you want) to be low, moly ring combined with a moly coated piston are great combinations. One last thing....he mentioned too, DO NOT RUN Full Synthetic Oil for at least one oil change on cast iron rings and maybe 2 on modern Moly Ring...that low friction lubricant will never allow the rings to break in. Your experience may vary...but after number 100 AMC Gen 2 engine under my belt this is what I have seen......another reason I will not patch a problem fresh built engine by another mechanic. It is a no win situation for you or the customer.

Ross, thanks for a detailed, thorough explanation.

Knew a crusty old timer that was a great farm truck car tractor boat mechanic kinda guy that could hear the knock or kill the spark Ina cylinder and tell ya where the piston was cracked the wrist pin loose or the rod bearing was loose. You know the old guy that smoked lucky strikes without filters and cleaned his greasy hands with Wesson oil not orange goop. He told me when I saw porous stuff like that to take a carpenters lead pencil and color in the pick marks and after running it in the holes would fill in. I also watched him stop old glazed up motors from smoking hy running Bon ami or Ajax water mix through theoyor to break the glaze on the cylinder walls.   He's the kinda guy that they made 002 under rod and main bearings for back in the day when you rolled your giggles and drank rolling rock and ate pickled eggs

The pitting won't affect a thing, I've puled old Ramblers out of the woods that had pitting in every cylinder and run them. No more oil use than you'd expect from a 100K or so engine... no more than a quart between changes (3K changes), which was considered normal back in the day even for a healthy engine. That vertical gouge might cause a little compression loss, but it's so far up it would be negligible. That cylinder might use a little more oil than the others, but not enough to worry about.

The tightness would worry me more. Make sure the crank is round and the right size bearings are in, and installed right. I've seen an engine where the crank wasn't turned and oversize bearings were put in after the owner measured the crank... or at least one or two of the journals. Uneven wear, or the guy didn't know how to read calipers, or maybe just didn't think 0.001-0.002 meant much...