I'm not a full time engine rebuilder, but I have dismantled a number of engines for parts. One had 88,000 miles on it and I was surprised NONE of the cylinders had a "ridge" in the top. Plenty of carbon, but no ridge. Just speculationg, but I suspect the opposed cylinder design provides plenty of cylinder lubrication, or maybe the Corvair cylinder material was quality. It's no secret the Olds, Buick, and Cadillac second generation thin wall blocks from the late 60's were superior in wear and strength to the Chevy big blocks.SpiderMan wrote: ↑Tue Aug 01, 2023 10:56 am Good points about the cylinders and the lip that forms with time. Makes sense about potential interference with the rings. I'll leave up to my air cooled guy. If the lip can be removed with honing only perhaps the cylinders/pistons can be reused. Otherwise I'm looking at buying a $ kit.
How do you guys feel about Heli coils?
I have a guy recommending I pretty much heli coil everything to do with head mounting and possibly beyond.
Heli-coils are fine for most repairs EXCEPT spark plug holes and block head stud holes. Those two location require a special Time Sert!!! One issue with the head studs is the last three or four threads have a "shallow" valley to seal (and bind) in the aluminum case!!! If you don't cut the stud threads to standard depth then the will lock up in the Time Sert BEFORE they are all the way in and there is a good chance it will deform the Time Sert and cause it to come out next time you take the head nut off the stud --- I've seen it happen!!! A helicoil will expand to accept an uncut head stud, but there is a risk it will turn back out when you loosen the head nut next time. I've only had to do a couple pulled head studs. NO FUN! Those head studs are TOUGH!! I had to order a top quality thread die that tended to bind on the stud with cutting oil!!!! An old machinist buddy said to use STP oil additive. IT WORKED, but very slow going to get smooth threads. Fortunately only 3 - 4 threads have to be re-cut to the proper depth. It is strongly advised that when you install the head stud into the Time Sert you use permanent Loc-Tite. NOTE: on long stroke blocks do NOT screw the head stud in past the inner block surface or the rod could hit it.
If you pull a head stud insert out, then the block is JUNK (too expensive to weld up and machine). Just my experience.