RING GAP POSITIONING: Piston thrust for flat 6 is?

My interest lies in the H-226 series and M-254 engines, and redeveloping them including state-of-the-art concepts; just sent my valve train parts to Ferrea Racing Components; finally getting into the buildup; utilizing the '51 226 first, and holding on the 254 for later.

"RING GAP POSITIONING: Piston thrust. This is the direction the piston head is
being thrust or “pushed” during combustion. Ring gaps should not be positioned
on the thrust side of the piston because the thrust side of a piston head
receives a lot more pressure and heat during combustion. Should a ring gap be
located on the pressure side, the increased heat and pressure (sharp corners at
the ends of the rings heat quicker and hotter) will cause the ring gap to vary
and affect the amount of ring tension against the cylinder wall. Piston thrust
can easily be determined if we think of it as being the leading edge on the top
of the piston head during the cylinder’s combustion cycle.
Example: A flathead V8 engine crankshaft rotates clockwise when viewed from the
front of the engine. Then the thrust side on all 4 piston heads on the drivers
side of the engine will be the side of the piston head furthest from the block’s
intake manifold surface. The thrust side on all 4 piston heads on the passengers
side of the engine will be the side of the piston head closest to the block’s
intake manifold surface.
Having determined the piston thrust, the ring gaps are positioned as
follows. Starting with the bottom ring........

(1) Oil ring expanders: This goes on first and the ends of the expanders are
not critical in location. Position as you will.

(2) Oil ring:
On 3 ring pistons, the gap is to be located at the center of the
opposite side of the piston thrust.
On 4 ring pistons, position the gap of the two oil rings 45 degrees
fore and aft of the center of the opposite side of the piston thrust.

(3) Oil ring segments (2 per oil ring):
On 3 ring pistons, the gaps are to be located ½" from the oil ring
gap. One fore and one aft.
On 4 ring pistons, the gaps are to be located ½" from the their oil
expander ring gap. Each oil ring will have it’s two segment rings located fore
and aft of it’s gap. Also see the following section SEGMENTED OIL RINGS.

(4) Bottom compression ring: Gap to be located directly over the wrist pin
towards the front of the engine.

(5) Top compression ring: Gap to be located directly over the wrist pin
towards the rear of the engine."
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I copied the above quote over from http://www.flatheadv8.org/rumblest/engine.pdf

I'll be using 3 ring pistons; my guess is that the thrust side of all 6 pistons is located passenger side, any disagreements?

(1) Oil ring expanders: This goes on first and the ends of the expanders are
not critical in location. Position as you will.

(2) Oil ring:
On 3 ring pistons, the gap is to be located at the center of the
opposite side of the piston thrust.

(3) Oil ring segments (2 per oil ring):
On 3 ring pistons, the gaps are to be located ½" from the oil ring
gap. One fore and one aft.

(4) Bottom compression ring: gap to be located over the wrist pin and to the rear.

(5) Top compression ring: gap to be located over the wrist pin and to the front of the engine.

Do these guidelines make sense?

Many people seemingly become anal when trying to determine the best spacing method for positioning ring gaps on pistons. The fact is, that an even 120°spacing between the rings starting with the top and working down to the oil ring has proven to be about as good as it gets. But here's a little rain on the parade. Anyone ever rebuild a 2 stroke dirt bike engine. Did you ever wonder why the pistons have a pin in the ring groove to locate the ring in a certain position.....Thats because the rings rotate on the pistons when the engine is running. Just like the valves in the head rotate as they open and close. So you can see how a lot of this type of anxiety is futile in a way. Because after you crank the engine up, in 10 minutes the rings wont be in the same orientation as you put them in when you assembled it.

Also, the major thrust side of the cylinders, is just the same as it is in any engine that has a clockwise crank rotation. Its the same as you mentioned for the V8 in the beginning of the post, the drivers side of the block as looking at it from the front of the engine. It's always the side of the cylinder that is on the leading edge of the crank rotation.

I heard it one time from an engine builder that the rings "move around", but no one has ever explained rationally just what dynamic force (s) there are that would cause it to "move around". Almost every engine I have ever torn down has vertical scoring in the cylnder walls, located only at the ring gaps. Seems to me that if the rings are"floating/moving", then there should be an infinite # of vertical scorings; I tend to believe that they are not moving/rotating, especially once seated, IMHO.

The piston isn't rotating, plus I can't visualize any other forces that would cause it to "move around".

On the other hand (valves), if the end of the valve is not perfectly square, and/or the cam lobe is not perfectly square/parallel to each valve end, then I can see the tendency for the valves to want to move/rotate a bit, but it does have resistance built into the valve train, depending upon the design. In 1951 the flat Ford six was designed to have the valves "float". It had a ceramic-looking cap that was on the end of the valves; this setup was on my M-254 when it was torn down, but the 51 H-226 had the earlier style valve train in it, and I could tell that someone had been inside working on the valve train as only some valves had been refaced - weird. I intend to get a photo posted, with Fred's help, of this latter design for every one's observation.

Over time, the rings might eventually stabilize and stop moving. I have worked for several Winston Cup engine builders, and these are just simple observations that I and others have made when we would have had a two or three week dyno test session going on, and you pull the valve covers about 20 or 30 times a day, and yank the heads off a couple of times as well. You can look down around the circumference of the pistons and see the ring gap on the top ring clearly, and notice that it moves quite a bit from where you put it when you assembled it. Even after a 500 mile race, and you tear down the engine, we saw that the top and second rings still have not become fully seated, so how many miles is that equivalent to in a normally driven street engine. One thing that contributes to the valve rotation, is the valve spring, they also rotate, and probably contributes to the valve rotation as well. Even after only two or three pulls on the dyno, you can pull the valve covers and most of the valve springs have rotated about a quarter turn from where you installed them. Pushrods as well spin when the engine is running, probably because the lifters also rotate. But with a roller cam, where the lifters cannot rotate, the pushrods still rotate, as evident by the guide plate transfer wear ring around the whole diameter of the pushrod. Whatever dynamic forces are at work that cause these things to take place are there, whether most people realize it or not. One thing that can make the rings move in a stock piston is the vertical clearance between the ring and the ring groove in the piston. The ring will actually flutter and bounce in the ring groove as the piston changes direction in the bore. On race engines of this type(Winston Cup), the ring clearance in the groove is lapped in the piston to have a tighter fit at the time of assembly. But lapping the rings isn't done to control or stop the ring rotation, its done to keep the ring from bouncing in the ring groove, and helping to maximize contact area to the cylinder. I guess the main point im trying to make is to just place the rings on the pistons in a 120° degree spacing between each ring and forget about it, because once their in the engine and running, they will move around quite a bit, and you can't do anything about that.

Rings move. Believe it.
Joe

M6, it sounds like you have an interesting project in the works, are you looking to do any additional performance mods to the engine.

X2... the rings will bounce around.

FWIW, when I build an engine, I don't think too much about it, since they're going to be somewhere else after operation anyway.

I just put the break in the ring expander over one piston pin end, stagger the gaps in the rails on the oil rings maybe 20-30 degrees either side of it, put the 2nd ring gap 180 degrees from the oil ring, and the top ring 180 from the second.

Anything trying to blow by has to travel halfway around the diameter of the piston. Not that it likely makes a lot of difference; I expect when you've got a thousand + PSI of hot air and burning fuel, it'll find the gap wherever you put it.

I just try to make it work slightly harder to have to leak through. But, since I gap every compression ring I install, I'm not sure that you could measure the difference on a dyno or timeslip if I lined all the gaps up in a row.

And, they'd all move anyway.

Right now, I'm a hell of a lot more worried about lifter rotation on my builds than what the rings are doing...

-Bill

CNC-Dude, I have lots of performance-enhancing plans: one thing that I want to do is pursue the LT1 concept called reverse- flow cooling technology, and I believe it can be adapted to the six's. It'll cost bucks but can be done.

http://www.fierolt1.com/technical_documents_main.htm

Let's think about this concept and figure out how to do this and we will have a wonder flatty that everyone at the car shows will gaulk at and wonder what planet it came from.

Of course it all sounds simple to talk about it, but maybe the simplest idea might be to reverse the rotation of the stock water pump, and put an impeller in the pump that also is opposite from the standard rotation. That might be a start.

I happen to have 2 of the LQ9 (LS) water pumps; one used and one new. However, these pumps are designed for 2 heads, not one, which presents another problem. It's been a while since I looked at the LQ9 water pumps; need to take a double take, but that option of incorporation is a long way down my list.

The idea of the 2-way thermostat needs to be incorporated, one way or another as well. I had thought of your suggestion already; this will takes lots of planning and thought.

A FEW MORE PRESSING CONCEPT IDEAS (from Baron's flatty V8; relieving and popup piston ideas) for PERFORMANCE are:

"The 7/16 popup piston is at 23 degrees BTDC, the point where its 60-degree chamfer starts to get the fire over the piston top to the bore's far end. Prior to this innovation, the flame would just go out on low-CR flatheads with weak old-style ignitions. With Baron's revised chamber plus a modern ignition, the pistons color much better. The latest thinking is that only the intake side needs a shallow block relief."

http://www.hotrod.com/techarticles/engi ... to_15.html

Which rod would you prefer?

http://www.hotrod.com/techarticles/engi ... to_05.html

How about a lighter and stronger Scat crank?

http://www.hotrod.com/techarticles/engi ... to_04.html

Of course one needs to incorporate FI, HEI and have a computer to optimize the end results. Like I said, a long way away for me, but I'll keep after it til it gets done.

Once it is all done it and proven to be reliable and durable, then it will be time to develop a stroked 254 w/turbocharging. There is almost no end to the possibilities with these engines, like any other engine.

CNC-Dude":3dcbsb8l said:

Of course it all sounds simple to talk about it, but maybe the simplest idea might be to reverse the rotation of the stock water pump, and put an impeller in the pump that also is opposite from the standard rotation. That might be a start.

Click to expand...

Hate to rain on the parade, but...

any centrifugal pump will pump from the center out, regardless of which way the impeller is turned.

Just turning it the wrong way will kill efficiency. But, it's still going to throw the substance it's pumping to the outside of the impeller.

There are electric water pumps used for drag racing, where they're plumbed in remotely; you could use these to pump coolant in through the cylinder head and then pick up coolant out the block.

BTW, I've had idle, random thoughts of applying megasquirt and a turbo to a flathead mopar six I have kicking around; think it'd be real interesting to see what some of the early engines are capable of with modern fuel/spark management and turbocharging.

-Bill