New OS piston clearance

[gaspumpsam]

Gregjo, thank you for your comment and insite. You are very right about cast ( softer) and chrome ( harder ) and when rings seat, cyl walls are smooth. Oil consumption, and compression loss, is hopefully at a minimum when walls are smooth.
When a cyl wall is honed, it could be (easily) .003” to .005” (as Lavoy pointed out in a previous post/comment) so when walls are smooth again, we have worn
.002” to .004” off the walls, and or rings( cast rings will wear more) . With the technology of ring manufacturing in the last 40 or so years, they are manufactured to as close to being circular as dammit is to swearing !! So why would we want to create wear in the first place. We save the time to hone( and the cost of honing stones and equipment) and make the rings and cyl walls seat
Immediately upon start up? And have rings run longer before rebuild because they didn’t have to wear themselves, to “seat”, or wear .002 to .004” off the walls.

We also save on extra oil it uses while breaking in. I think the biggest external “good thing”, is when we get our project, or “baby” rebuilt and running, and we are showing it off to interested( there external expression) and their internal expression(is they are critizeing your work, and/or comparing to the one they just got running) , you don’t have to be afraid to start it in your shop, because of smoke out the stack, or to remove oil fill cap, as engine running , and have it puffing and smoking like it is maybe an air compressor!

Happy Valentine’s Day , everyone!!

[gregjo1948]

GAS---- If, indeed, you get .003-.005 wear upon break-in/seating, it is so minute in relationship to a bore of 3/4/5/6 inches. When installing the rings notice the amount of compression that is needed to slide them into the cylinder. After installed the end gap should be measured to assure that its within specs. That .003-.005 isn't going to make a squat of difference. Happy Saturday

[original possum]

An increase of .004" on a diameter of only 3" would make the ring gap (circumference) nearly 0.010 larger unless my math is wrong.

[gaspumpsam]

Yes, you guys are right on the end gap measurements etc. I don’t believe end gap is to critical in our situation, as long gap is not to tight to start with.
I believe a post from Lavoy say’s piston’s for a 440- gas, when available are in 3 sizes, with .045” OS., being one size, but rings aren’t available in .045” OS , so it ok to use .040” OS rings on the .045 OS pistons( so ring gap wouldn’t be to critical.)

The two engines I have on the go now are a 1953 Dodge flat head 6, the owner is putting in a “rat rod”, I don’t particularly like rat rods, but the engine will be nice- we have rebored(.060”) new pistons and rings( chrome), a little bit of a cam, 2 carb intake and headers.
The other is my JD 440ic, gas, rebore, new pistons( not JD, but look and measure identical) perfect circle rings,
Both had bad walls, so had to rebore. So I won’t be able to comment about my not honing therory, on these two engines, other than how they start and run.

[Lavoy]

.045 rings are readily available, 040 would be more rare than .045 today.
Lavoy

[Ray III]

The whole point of honing is to cause oil to stick to the walls, improving lubrication and ring seal. If you are getting bad results after honing, maybe you should let a machine shop do it.

[gaspumpsam]

I guess that is one therory of why cyl walls are honed.

I don’t have bad results, because I don’t hone. As I stated, I remove top ring ridge ( to get piston out ) and if walls are relatively ok, install new rings etc and go. No oil burning or blow by. ( I have rebuilt many, both gas and diesel, liners or not, and have not had any problems from not honing, chrome or cast rings,)

The machine shop that discovered this was the most well equipped , modern, with excellent machinists, .