You misunderstand. They cylinder below the ring ridge is true all the way down. They rings don't go all the way up in the ring ridge.This is telling you the cylinder walls have .009 inch taper top to bottom. By the book this is beyond the range of a worn out wall by almost 2X.
This is appearing as a step rather than gradual taper but this ain’t good. At the absolute minimum this ridge needs to go, the risk is busting rings.
Bogie
I have called 3 different engine builders and they have all told me similar things as far as ring gap. Their is no bore taper at all. Essentially my whole point of this threat is to ask about what appropriate ring gap would be. Yes their is some ring ridge. Not much maybe .006 difference between ridge and actual surface that ring is on.I don't know any reputable mechanic/ engine builder worth his salt who would re ring an engine with that much west or a ridge left in the cylinder . What does your dial bore gauge tell you about cylinder taper ?
I learned this on a Briggs Stratton engine when i was about 12 yrs old. That engine smoked a huge amount after a few minutes with new rings. That was 58 yrs ago..The ring ridge is there because it bottom edge is where the rings stop at TDC. The risk is for any reason the top ring exceeds where that ridge starts the ring likely gets busted, that ridge is a hard stop. It really should be removed If you’re that deep in the engine.
Bogie
Yea I understand. I decided to take it to the machine shop and let them take care of it. 600$ is not too badNothing terribly wrong with that gap amount, it's on the high side but allowances for running it higher performance than stock is common.
"better to be a little to big, nobody will know.....than to be too small, then everybody will know" is an old repeated phrase.
You absolutely have to do something about that ring ridge though, it has to be removed or it will quicky kill the new set of rings because the new set will be a few thousandths of an inch thicker compared to the worn thinner originals that made that ridge....comprende?
Plus if you turn more rpms than the typical rpm that created that ridge the parts stretch and flex that comes from running a higher rpm hammers the new rings against that ridge even harder.
Rebuilding my 406 as some of you have probably seen. I need some verification. My ring gap all the way up and down the cylinder is .025. At the very top of the cylinder where the ring ridge is is .016. I was told by a very reputable engine builder that ring gap on a 406 should be anywhere from .024 to .028 on a N/A motor. If that is the case it sounds like I'm good. I'm wondering if that is correct before I finish this engine. What are your opinions?
That's crazy because the machinist I took it too said that gap was about right for a 406 sbc. Also about 3 other machinist told me similar things. And also the KB piston head formula tells me that I want about .024 piston ring gap on a stock application. That's the hard part about these sites you get 50 thousand different answers.My forged diamond pistons (4032) calls for 0.0045 per inch for naturally asperated. I would purchase rings that require gapping and you can get it right. 0.024 to 0.028 sounds like power adder gaps.
the KB piston head formula tells me
Interesting analogy...Rather like silicon enhanced ladies are hard to hang on to, there one day gone the next while those with the natural product tend to complain a lot but hang in there.
😂
You are encountering some differing views on this topic. You might be OK and you might be getting some wise counsel. Of course it is your choice. For example if you are using used pistons, you likely have some ring land wear and may be fine. If on the other hand you are using new pistons along with new bearings, you just might be pushing those piston rings a wee bit higher in the cylinder and those new rings might be hitting that ridge. If that is the case and you are using cast iron rings, not chrome moly, you may well break a ring. Of course the decision is yours 100%. I have heard the advice you received from my first engine rebuild in 1965. I have done it both ways and have yet to have an issue. I think you have a decent chance of it working. That said you can also remove the ridge fairly easily with a ridge reamer. In either case your engine will likely run just fine. Your original question on end gaps sounds just fine.I have called 3 different engine builders and they have all told me similar things as far as ring gap. Their is no bore taper at all. Essentially my whole point of this threat is to ask about what appropriate ring gap would be. Yes their is some ring ridge. Not much maybe .006 difference between ridge and actual surface that ring is on.
