Ring gap

I am with shortbus on this. I am STD bore on the puller and have always use .020 rings and file fit them. It is high compression with zero blow by. I just tore it down after the season and could see about an inch of the top ring where the piston broke sometime this season. I had zero signs of this and motor ran great. I am running total seal second ring. On a DD without total seal this may be different (doubt it). I wouldn't be one bit afraid of doing it.
a56218acfdf20f6c88b23eb4ee1e9994.jpg
 
Keep in mind that if you're set for .010 PTW, you're no longer a .020 over engine. So neither the .020 or the .040 over rings are a perfect match. I used .040 over rings on mine, but it's too early to comment much on blow-by yet. It has some, but with .030 end gap and high compression, it's about what I expected.

I understand what you're saying being out of round, but with only a .016" difference between design and actual, it's hard to believe that it would have a significant effect. I was actually more concerned about increased wall pressure from the larger ring.
 
You are talking about .020 on the circumference of a 4" bore. It will not impact the concentricity of the circle near as much as you are all thinking....
 
Why does the book state not to file top ring? Weird. Going through my block now. All top rings started between .018 & .015. Thinking of opening the 2 .015's up a touch.
 
Pudge said:
Mahle rings? Every set of over bore rings have been way on the high side out of the box that we've used.
Also, .001 extra bore = .003 ring gap
Click to expand...

.001=.001*Pi to be exact
so .001=.0031415....

Just throwing it out there, although I'm sure you knew that.

shortbusdriver said:
Just use .040" over rings and file to fit.
Click to expand...

I'm sure OP has done this more than me with much higher HP applications (<600hp), but this has been my experience in mostly daily driving applications (with weekend fun stuff), and I've never had an issue even at much higher miles (100k+).

zfaylor said:
You are talking about .020 on the circumference of a 4" bore. It will not impact the concentricity of the circle near as much as you are all thinking....
Click to expand...

X2
4" diameter is 12.56637061" parameter
with a .020" gap is .5% change in the parameter
with a .040" gap is .503% change in the parameter from .020" to .040"

We're talking about less than 63 thousandths of an inch every .020". I'd say it's extremely unlikely you're going to get a hot spot on the opposite side of the gap with this.

On another note, do you guys just set gap to manufacturer specifications, or have you ever looked at expansion rates of materials at the heat range you're typically going to see and made up your own? I've always been tempted to do this, but don't make enough money to feel comfortable experimenting. :hehe:
 
I'm just going with the total seal info sheet. I don't make enough to play around either.
 
Just throwing in my$.02. I file fit oversized rings (not sure if it was .020 or .030 it was years ago). It was a budget rebuild. The end gap was fine but one ended up cracking in short order. It cracked exactly opposite of the gap. I've not tried that move since.
 
You must log in or register to reply here.
Back
Top