[Mailman]

I am in the process of putting my 73.5 bore cheetah together. I was wondering if you think .010 for a ring end gap is too tight. The cylinder has a fresh replate and the rings are new also of course. I can't remember what I was running before.



Do you guys think this is a little too tight for this bore? What end gap do you run and what bore size also?



I know the general rule is .004 per inch and my bore is approx. 2.9 inches which puts me at about .0115 according to "the general formula".





Mailman

 

[REDLINE]

I would not go smaller than .012 myself mailman. There is little to nothing to gain from going smaller, and a lot to loose. If those rings get hot enough to expand past what the gap is, they will then bottom out and push into the exhaust port and catch the upper or lower edge on the way through.

 

[Radar]

Exactly what Redline said. .010 is a little close. I set everything at .012 even little 40mm pistons.

It's very important not to ride the heck out of a new build untill the rings smooth out the bore completely, when breaking in the rings they are moving across an abrasive surface of the bore and they can get hot which can make them lose tension as well as expand and close the end gap.

Your rings are then slightly too big for the bore size and will catch on the edge of the exhaust port and make you

.

 

[REDLINE]

Good point Radar, I like to coat the cylinder walls with atf, as is has a friction modifier (grit) that accellerates ring wear to try to seat the rings as quickly as possible too.

 

[Mailman]

Excellent Responses! I will file them down to .012. Thanks guys.





Mailman

 

[dajogejr]

Good point Radar, I like to coat the cylinder walls with atf, as is has a friction modifier (grit) that accellerates ring wear to try to seat the rings as quickly as possible too.

That's a new one...Bill. Very nice.

I actually broke in my fresh top end this year on gas. A couple good heat cycles....

 

[REDLINE]

If you have the time, and the carbs, that's the way I prefer to do it Dave. You get higher cylinder temps out of gas than alky, so those heat cycles and first few pulls go a lot further towards tempering that fresh aluminum on those new pistons.