Four ring pistons
 

I am building a 258" (stock stroke, 3 5/16" bore) flathead. I had a bunch of stuff laying around, and when I had the opportunity to buy a set of pistons from Speedway's garage sale for a little over $100, I was able to procure the last major component I needed. I have everything gathered up, ready to go to the balancer. I have read several places that stock type four ring pistons can be run without the bottom rings to reduce weight and friction. As I remember hearing it, the old timers would save the unused bottom rings and install them in a subsequent rebuild for a cheap refresh. At my age, I doubt that I will put even 5K on this engine when finished. Is there any validity to this theory? I need to know before I send the components off to be balanced.

Re: Four ring pistons
 

If you have all cast iron rings I wouldnt be concerned. More power comes from
a 3 ring setup with molly rings.

Harry

Re: Four ring pistons
 

I have done that a number of times. Just toss the fourth ring. When you install the piston, you definetly notice the difference in drag without that 4th ring.

Re: Four ring pistons
 

Those who think the lack of the bottom ring will somehow cause the piston to rock-leave out the 3rd oil ring and just run the bottom one.

Re: Four ring pistons
 

So why leave it out or keep it ??
It was put there to keep oilcomsumption down...if it is adding to wear by taking to much oil away has been battled about.
For it to prevent pistonslap it has to be an expandertype otherwise it will float in the ringgroove.
That it will steal away a lot of power by adding drag....cant be the real make or break of a stock engine.

Re: Four ring pistons
 

3 rings are enough, especially with modern rings and with todays oil. The decrease in friction when going from 4 rings to 3 is significant and worth doing.

Re: Four ring pistons
 

I don't disagree on the lack of need for the second oil ring, but I would wonder what you all are considering 'modern rings'? Many of the ring sets that I see are not modern (Grant, Hastings, etc) - they're the same stuff that was run 60 years ago (for 3/32, 3/32, 5/32 or 3/32, 3/32, 3/16 groove widths). Only certain piston sizes have the option of modern ring availability - at least from what I've seen.

Due to this, I try to order pistons with the 1.5, 1.5, 3.0 mm ring sets (true modern stuff) - or even TotalSeal gapless ring sets.

Anybody know about modern ring sets and the standard sized piston ring grooves . . . anybody make anything truly modern (Like moly upper rings).

Just curious . . .

Re: Four ring pistons
 

Many years ago I asked the same question to the mechanic at the rebuilding shop (50 years ago) and he said that the new 3 piece oil ring was he way to go. the reason for the two oil rings was, because one just wouldn't do the job. I don't keep up with what's new, especially the rings available for our flatheads. However, I bought a set of .020" over 3 5/16 pistons from Egge and they came with metric rings from a Volvo. I was impressed. The 280 Ci engine is stock except for EAB heads milled for .050 piston to head clearance . Crankinf pressure is 160

Re: Four ring pistons
 

I pulled out the rings that came with my Speedway pistons so I could see what I have. the first picture is of the rings that are supposed to go in the fourth (bottom) groove. They look like they are cast iron. The second picture is the rings that are supposed to go in the third groove. These look to me like the "3 piece oil ring" Ol' Ron was referencing. The last two pictures are of the rings for the top two grooves; they are identical and appear to be cast iron as well.

It looks to me that the fourth groove rings are superfluous and can be left out. I think the only thing I would worry about is oil control. I don't think piston stability in the bore would be a problem given the length of these pistons. I have seen pictures of SBC stroker pistons with no bottom rings that are so short it's scary.

At this point, I am planning on leaving the bottom rings out and having the assembly balanced and assembled without them. If anyone thinks this will be a problem, please let me know, as all of this is going to the machine shop on Monday. In case it matters, this will not be a stock engine, but will have an Isky Max-1 cam and kit, properly machined Edmunds heads, two 94's on a Navarro manifold, an old Mallory flattop distributor, and headers.

Re: Four ring pistons
 

Using those style ring will eat up a lot of horsepower maybe as much as 20 or so.

Harry

Re: Four ring pistons
 

First, this is just my opinion, but let's think logically for a moment. I believe talk of reduced friction as the result of eliminating the fourth ring, or as encouragement to delete the fourth ring, is total nonsense. The difference in perceptible friction as the engine is turned by hand has no bearing on the amount of friction occurring in a running condition. Rings, like everything else in a running engine, float on a film of oil. If they didn't, they wouldn't last two days. You can delete the fourth ring, but why if you have it on hand? JMHO

Re: Four ring pistons
 

These are what I have; I'm just trying to make the best of it. I have done quite a bit of searching, and I can't seem to find anyone who supplies "modern" rings for the older style pistons. If you have a source, I'd sure like to know about it. At this time, another $500 for pistons and rings ain't in the cards.

Re: Four ring pistons
 

Where did the myth about the fourth ring somehow "stabilizing" the piston come from? Since rings float freely in their grooves, there cannot be any stabilizing effect. Actually, one job of the piston is to hold the rings square in the bore, not the other way around. As far as using an expander in the bottom groove, the small amount of tension they add is overwhelmed by the weight of the piston and the forces of inertia, not to mention the hundreds of pounds of combustion pressure on top of the piston.
So there is no validity to this myth at all!

Re: Four ring pistons
 

I'll have to disagree with you. The rings constitute roughly 25% of an engines total friction loss. That extra ring definetly adds to the friction in the engine. Today's ring manufacturers are developing ring coatings to reduce the friction caused by the ring. If ring friction was inconsequential, I doubt they would be spending money in research and development in this area.

Re: Four ring pistons
 

Lets see if im all wrong here...
First and second compression ring sees most of the pressure and has the highest pressure against the cylinderwall.
The forth ring that is an oilring with holes going into the piston that lets oil and pressure pass easy and will not have the same pressure against the cylinderwall.
That the 4th ring would make a big difference...id like a dynorun of that.

Re: Four ring pistons
 

Why don't you call the ring manufacturer and get the info from the front of the horse and not what some post on internet forums. It's not rocket science once they tell where its at.And it is a toll free number be sure to state you case as to application and ask for technical support. You may be enlightened. I know what they are going to say but best you hear it from them. :)

R

Re: Four ring pistons
 

Please enlighten me Ronnie !

Re: Four ring pistons
 

Where do you get these hp loss numbers? 20 honest horses taken from a regular street flathead is a damn Big chunk!!

I have a thought on the four ring setup and why it was used originally. Cylinder wall finish was, according to contemporary literature, mirror finished. Was the reason the fourth ring was added to try and control the oil getting passed rings that couldn't "bed" into the cylinder bore, due to this "mirror" finish? The early flathead's had three rings, then went to four. The early flatheads were plagued by high oil consumption.

As we now have a honed much rougher finish, those soft iron rings now bed pretty much straight away. And obviously control oil much, much better than the mirror finished set up. If this is so, I believe that fourth ring is redundant.
Any thoughts on this chaps?
Martin.

Re: Four ring pistons
 

You should take a second look at the compression rings as they are not the same. This is an example of what i said in an earlier post as to believing what is posted in a forum.I appears there should be an instruction list in the ring set what does it say?? The ring set looks to be a #533 Hastings or equivalent.

R

Re: Four ring pistons
 

Back on the 60s I built a stock car 47 ford coupe narrowed and channeled, I built 52 Chrysler Spitfire 261ci, bored it .125 and used 235 Chevy pistons. A ring rep came into the shop, I asked him what I should use for rings, he said your looking for less friction, use chrome rings. The chevy pistons stuck .070 over the top, I chopped .035 of the top of the pistons, dual carb and split headers. That was one screaming engine, no problem breaking in the rings in a stock car track. Walt - BTW, we used .010 pistons clearance back in those days.