Metric Ring Sets

Shoebox

Shoebox

Well-known member
I feel the need to ask my Dumb Question of the day. Regarding metric ring packs for the V8s, is what's metric the ring widths- 1.5, 1.5, and 3.0, or are the bores going to be metric, not the usual .030, .060, etc, over bores? I suspect I know but have to ask. Thanks.
 
They have way less friction and seat almost immediately. I have the in all 3 of the engines I built, and they are in the Ardun engine in the car I bought.
 
The circle track guys use a 1mm, 1mm, 2mm packs. Engine builders claim they hold their shape to the bore very well. Don't know if they are available for flathead pistons in those thicknesses, but probably in the 1.5,1.5,3mm sets. It would take a piston special made with that ring gland. Bored & Stroked could chime in, I believe he uses them from Ross.
 
Still don't understand about metric ring packs. So now Shoebox doesn't have to be the 'dumb question guy', as I still don't get it. Are they thin rings stacked up in the lands? But they'd still need to be sized for our bores.
 

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Thanks for those links Big D, I have now entered the 21st century on the use of metric and thin ring packs. With my 40 mph speed limit here I still feel ok with the cast iron hastings in my recent 276 build, but those are some sizeable advantages I just read about. Yes, 7.5 hp for 200 bucks coupled to less wear is a winner.
 
Little less weight for the inertia change up, less wear on parts because of less drag too. Worth reading.
 
They stay conformed to the bore better too. I have only heard about them used in performance builds, no idea on longevity as in 10s of thousands of miles. The wait time will probably discourage most.
 
I am very skeptical there is much of any horsepower to be had below 3,000 rpm from metric rings in a flathead. The Engine Masters show did a back to back dyno comparison where they took a small block, tested it, swapped otherwise identical pistons with metric rings, and tested it again. There was no measurable difference below 4,000 rpm. For members who want the most out of their engine way up in the rev range, then metric rings are an improvement. For members who don't drive that fast, or who like me who install overdrive and simply up-shift, there is little point to spending all the extra money.
Here is the link to the back-to-back standard vs metric ring test video, nice comparison graph is at 8:40 in the video: https://www.youtube.com/watch?v=-29IWc-zrv8
 
You only need to run the top 3 rings on 4-ring pistons. I've done it a couple of times with no problems. Current (hell, 50 year old) ring technology has made the fourth ring superfluous. Also, the extra cost and trouble running metric rings aren't worth it unless you're seriously into racing. If I had extra time and extra money, I'd run 'em, but everything seems to be in short supply today.
 
What is also important is to consider the diameter of the metric rings - before you bore your engine or order pistons. I typically determine the bore diameter that corresponds to the available ring diameters and ring types I want to use, then custom order my pistons. If you speak with the application engineers at the piston manufacturer, they will be able to tell you which types of rings they can supply for a range of diameters.


Sometimes the diameters align fairly well with what we're used too ---> 3 5/16 for example --> 3.3125. is pretty close to 84 mm -> 3.307 or 84.5 mm -> 3.327. Depending on the ring manufacturer, they may supply rings that are millimeters in thickness, but with inches-based diameters.

One of the nice things about looking for rings first is that you may find a ring package that gives you an overbore that is less than you would have had with typical inches-based ring packages:

Example: 85 mm -> 3.346 inches. This is about 1/2 way between a 3 5/16 bore and a 3 3/8 bore.

Also, there are many types of ring packages --> cast, steel, moly coated, gapless oil rings, etc.. There are many ring options if you look at catalogs and associated applications --> street, performance, boosted, racing, etc..

Here is a Total Seal catalog - has some good information:


View attachment TotalSealRingCatalog.pdf
 
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