Metric Piston Rings?
 

Okay, I'm finally going to ask just what they are and what's so slick about them? Google didn't help with anything I could understand. Real thin rings with lower friction, I guess? Thanks!

Re: Metric Piston Rings?
 

Right on both counts and lightweight! Approx 23 grms/per set vs 65+ grms/per set on the conventional 4-ring cast pieces!

That's a nice "positive". Another "positive", they are worth some add'l HP. Need the proper finish on the cyl walls.

And most (if not all) are "moly", for quick seating and less "drag". You can feel the difference between the "cast" and the "moly" during the piston installation, takes much more effort to turn the crank with the "cast" rings as each one is put in.

Thanks, Gary in N.Y.

P.S. About 99% of our builds now get the "metrics", most get Ross pistons to go along!

Re: Metric Piston Rings?
 

Thanks, Gary!

Re: Metric Piston Rings?
 

So is there a conversion chart depicting which size metric rings for a certain bore size?
And what is the proper install, cylinder prep, and break in procedure? And can they be used with any piston, not just the high end Ross? Sorry for all the ?, never used them before.

Thanks,
Ralph

Re: Metric Piston Rings?
 

The metric rings and pistons are a match, a metric ring requires a piston made for metric rings.

Re: Metric Piston Rings?
 

It´s not the metric ring size that sets bore finish...It´s the plasma moly coating of the rings that calls for a finer finish of the cylinder walls since they don´t need the same break-in as a cast iron set.
You may get 5% max increase in hp from a low tension plasma ring set...so if you don´t need forged pistons which makes more noise...i spend my money elsewhere for better bang for the buck...

Re: Metric Piston Rings?
 

You can purchase inch-sized rings made with the same materials and coatings as metric-sized rings. There isn't anything special about the latter.

Re: Metric Piston Rings?
 

Being I just went through this, the price difference between Egge with cast rings and Ross with metric rings is $220. Certainly not a small amount, but using the 5% power increase, lets play this out.

I think it's reasonable to say that a performance-built 276 engine can get 150 h.p. fairly easily with the "normal" parts. Multiple carb intake, cam, heads, larger valves, porting, etc.

Using the 5% increase using metric rings, that equates to a 7.5 h.p. increase.

Adding all the gains up, I'd pay $200 for a 7.5 h.p. gain.

After much discussion with Ronnie, we decided metric rings were the way to go since the block is at 3 3/8ths + .030. I want to prolong it's life as long as possible and the wear properties of metric rings are much better than the "tradition" fractional cast rings.

Re: Metric Piston Rings?
 

If one were to buy a new set of cast pistons these days with "inch" rings, what are the chances that the rings would be moly? It would seem to me that if the technology is so much better than cast, the contemporary ring manufacturers would have switched to it a long time ago. If the "inch" rings are moly, I would imagine that the HP difference would be negligible. Does "inch" always mean cast iron and "metric" mean moly? Inquiring minds want to know.

Re: Metric Piston Rings?
 

When I spoke to Egge, they were cast rings. I didn't inquire with them if Moly rings were available.

I will also add that a part of my decision to go with Ross was to also allow me to add a blower down the line if I choose to so. I wouldn't mind adding a Scot-type blower once my bank account recovers from this build.

Re: Metric Piston Rings?
 

I think I still have the 8 "fourth" rings that I left out when I did my last build. Is there some way I can determine if they're moly or cast? In the alternative, if I were to send them to someone, could they tell me?

Re: Metric Piston Rings?
 

Do you know who made them?

Re: Metric Piston Rings?
 

Are these the old style one piece oil rings, or modern three piece (rails with expander)? If three piece the rails are chrome faced, I believe.
Most sizes of the older fractional "inch" compression rings have been available in cast, chrome, or moly for many years. The plain cast have a dull gray finish, the chrome are shiny, and the moly have the molybdenum embedded in a 'groove' in the face of the ring. Looking at the face of the ring, you can see the moly in the center of the ring, with the cast ring material on the edges. So they're actually "moly-filled" rings.

Re: Metric Piston Rings?
 

Not so much about inch or metric as about going for a more narrow ring.
You need a certain amount of pressure / area to seal and with less surface( narrower ring) you need less pressure=drag.
Then it comes down to right ring in the right place...cast iron is the basic all around.
Chrome is a pain in the rear to break in and get to seal but in dirty enviroments like construction equipment and perfomance engines in a real dirty enviroment they still are first choice.
Moly is a cast iron ring that has been plasma spray coated with moly.
Real good for reducing friction...but can´t deal with real hard heat...so in nitrous and real mean turbo setups they have a hard time...
Same as you can´t run anything but hardened cast iron valve guides when serious heat is involved...a bronze guide melts...
I just put togetter a porsche engine and the 3 piece oil ring is narrower then the compression rings on a metric flathead piston...:D:D:D

Re: Metric Piston Rings?
 

No.

Re: Metric Piston Rings?
 

Typically the metric ring packs for flathead pistons use a 1.5mm, 1.5mmm 3.0mm ring package - obviously the pistons must match. I prefer these rings over the good ole' Grant and Hastings rings I used to run. To me, having a nice set of Ross forged pistons with quality metric rings is the way to go - assuming you can afford the slightly higher costs.

In the grand scheme of flathead things . . . I've found this cost difference to be the LEAST of my overall build-cost problems! LOL

Re: Metric Piston Rings?
 

I should have taken a picture, but the difference of the metric ring packs is dramatic when compared to the older style.