Three ring pistons

[Tony WestOZ]

Hi thought I`d bring this across from the truck side in the quest for more information..

I am currently stipping down a NOS 250 long block I have had in the shed for 20 years. I believe this engine is an English made motor. Australia used them from 53 to 62 instead of the Canadian long block motors that had been used before 53.

However a few things have come up that I have not come across on a flathead before, in Australia.

One of them is three ring pistons.

Does anyone knows when 3 ring pistons came into use on the flatheads?

I have only ever seen 4 rings on a flat head before.

[Andydodge]

Tony......thought you were talking about a 3 ring circus........lol.........nope, never seen a 3 ring mopar flathead piston......where did you get the engine from?.......I know about 20-25 yrs or more ago the NSW branch of the Australian Chrysler Restorers Club got hold of the last of the flathead sixes that Chrysler Australia had for a very cheap price and sold them to club members............I had heard that these engines had some unusual parts but can't remember what it was..........what bore is this engine?......3 & 7/16th?......... andyd

[daddyo23]

A shop that did my motor used three ring pistons on my friends '37. He was not happy about that at all. He's keeping a close eye on it. With mine, they didn't pull the back frost plugs or that allenbolt in the back when they "cleaned out" the block. They also used a non-Mopar rod for the one that was bent too bad to straighten. Within 500 mikes the motor was back out with spun bearings and the same rod bent. They tried to charge me with re-doing the motor but after a couple of lively discussions they took care of it. When I picked the motor up there were new plugs in the back and sealant on the bolt. They said they used four ring pistons in mine. This shop was suggested to my friend and we thought we would try it. Never saw any of thier work but heard they were good. Needless to say, that place has lost my business.

[greg g]

sitting next to each other like that certainly shows the amount of metal above the top ring on the three ring piston to good effect. It looke like thay would be a lot more resistant to the broken rings and chewed up pistons that several of us have found whe when we pulled the our engines down. I wonder if they are an truck only HD application of military spec.

[Don Coatney]

sitting next to each other like that certainly shows the amount of metal above the top ring on the three ring piston to good effect. It looke like thay would be a lot more resistant to the broken rings and chewed up pistons that several of us have found whe when we pulled the our engines down. I wonder if they are an truck only HD application of military spec.

The 3 ring pistons would add to displacement but subtract from compression ratio when compared to a 4 ring piston.

[Tony WestOZ]

When I bought the engine 20 years ago I was told by the guy it came out of Army surplus. Never put much stock in it even though it was green.

I did have the thought that it might have come from the several container loads of Power Wagons stuff that came into Australia in the 80`s. Ex Israli army, or so the story goes.

The rear seal is another one.

The NOS motor has the 2 piece rubber seal (on the right hand side of pic) that was introduced in the US in 53. The other seal in the pic is the only type of seal I have seen here. It takes 6 bolts to hold it in place and it came out of a 1960 engine.

One things for shore, the NOS has the lowest compression of the 3 engines I just stripped down.

6.1:1 compared to the 6.5:1 of the 1953 engine and 6.9:1 of the 1960 engine.

[Frank Elder]

That green color looks to be a Jasper remanufactured engine...look for a big J stamped on or near the serial pad.

[greg g]

You might want to send a note to Vintage Power Wagons. Thay had a bunchof those Isreali surplus engines, and may be familiar with thier internals. It's interesting to see you measuring cumbustion chambers on the bench. there have been several posts lately regarding how thick the original heads are, so people can tell if they have been milled during their lives.

It might make sense that the military engines would have a lower compression ratio. That would allow them to use whatever gas they found available regardless of octane or lack there of.

What were the results of your measurment as regards the volumn of the combustio chamber.

For Don C, please splain how the ring position would effect displacement. I always thought that was determined by bore and stroke.

[Don Coatney]

.

For Don C, please splain how the ring position would effect displacement. I always thought that was determined by bore and stroke.

It seems to me that there is a difference in the location of the top ring on a 3 ring piston compared to a 4 ring piston. This extra space on the 3 ring piston will increase the volume of the cylinder. Displacement is volume. At least that is the way I understand it.

[greg g]

The volume of the cylinder is set by its domensions. the volumn of air displaced or compressed within the cylinder is determined by the travel of the item (piston) within the cylinder. If anything the difference in the location of the ring down further on the piston would actually yield a small amount of space for the air fuel mixture to get into actually lowering the amount of compression the piston could exert, thereby increasing the uncompressed volumn and decreasing the swept area. But it would probably be insigificant.

Where is stroke measured, the top of the poiston or at the wrist pin is that measurement the same??? What about a domed piston, that increases compresson but not stroke. If measuring from the top of the piston the bulsge would actually decreas the stoke as its starting point would be further up in the cylinder.

I think I have already thought to much about this and my head is beginning to hurt.....

[Plymouthy Adams]

The top of the piston is the measurement in CID same as for CC measurements..though the rod travel is the actual length it is the same at center of the piston as it is at the top of the piston unless you have some really irregular pistom domes.. I believe it was Don's point..the position of the top ring in distance from the top of the piston in relatation to the other piston could cause volume/CC issues howsoever insignificant it will be...in other words..if the fit of the piston be it 3 or 4 rings is correct for stoke and bore..the ring count is not an issue either as the design and material of the rings in later years are far superior to the old stuff..add such stuff as plasma coating, molybedilumdysulfide(sp) etc etc

poersonally thinking in my last look see at these the 3 rings actually give you a better piston land area for less chance of damage due to more material to buffer the shock as the cylinder changes direction of travel..the old 4 ringers get beat to death..

[Tony WestOZ]

OK after a bit of a side track (this working for a living now certinly takes up your time) a couple of more things.

greg g, to answer your question.

Cylinder Head combustion chamber volume, head thickness and approx ratios are as follows

Nos, 6.896 cu", 1.966", 6.2:1.

TE7, 5.639 cu", 1.888", 6.9:1.

KEW, 6.066 cu", 1.925" , 6.5:1.

I have since found that the NOS engine is milled 0.010" lower than the early blocks.

The letter A is stamped on the top of the block. Wheather this means it is standard or its had to be machined an extra 10 thou to get it flat, I don`t know.

Roughly worked out that if I use the head off the TE7 engine, the thiner head gasket off the Nos engine I could end up with about 8:1. Interesting.

I am lucky that I have stripped this NOS engine down as there were two major problems that would have led to am early dimise.

1

the oil slinger was on the wrong way. It meant the outer edge of the slinger was rubbing against the timming chain. For the little running this engine has done there are already were marks on the slinger.

2.

Bad enough there would be little iron fillings from the slinger getting around in the oil, but the oil fiter was plumed up in a way that it would never have filterd anything.

This engine (like Don C`s Desoto) has the machined area and modifications so it can be converted to a full flow system or left as a by-pass system.

The trouble is, this filter (which should be set as a by-pass) was fitted the wrong way. Both the in and out lines for the filter are plumbed into the same oil galliery. The return line should have gone into the hole below and to the right of where it is in the pic.

Below are the two different pressure relief valve set ups.

The 3 pieces on the left are from the normal by-pass set up. The 4 on the right are for this engine to run a by-pass sytem. To get the full flow system to work I need to plug up the main gallery so I need to add an extra plug. Then I can run full flow and a by-pass filter.

Now I have got go out and put a couple of engines back together, its starting to get congested.

Edited December 12, 2009 by Tony WestOZ