Don Terrill’s Speed-Talk

I've done this on an injected nitro motor in the past, but I think that's a lousy barometer.

Have any of you run the wrist pin above the oil ring, about .030 into the second land, and what was the effect on oil scraping?

I'm doing 4.000 stroke Cleveland kits and I do not care for the 6.000 rod in that application and I'd like to use a 6.125 to keep more (or some) skirt in the cylinder at BDC.

Mark O'Neal wrote: ↑Wed Mar 25, 2020 12:17 am I've done this on an injected nitro motor in the past, but I think that's a lousy barometer.

Have any of you run the wrist pin above the oil ring, about .030 into the second land, and what was the effect on oil scraping?

I'm doing 4.000 stroke Cleveland kits and I do not care for the 6.000 rod in that application and I'd like to use a 6.125 to keep more (or some) skirt in the cylinder at BDC.

I have seen it done with little pins in the oil ring groove keeping the oil rails from rotating; similar to a 2 stroke.

Mark ,
I have done it before using pin buttons . "I" don't like it because we try hard to keep oil from migrating above the oil ring and putting the pin above the oil ring provides a pathway for oil to go above the oil ring easily. If you went to a 1.2x1.2 top and second with a .250 down top ring , it would work. I did one that way "once". The rods bolts will hit the bottom of the bores too. They don't with the 6". I don't need to tell you how to make pistons LOL

piston guy wrote: ↑Wed Mar 25, 2020 11:39 am Mark ,
I have done it before using pin buttons . "I" don't like it because we try hard to keep oil from migrating above the oil ring and putting the pin above the oil ring provides a pathway for oil to go above the oil ring easily. If you went to a 1.2x1.2 top and second with a .250 down top ring , it would work. I did one that way "once". The rods bolts will hit the bottom of the bores too. They don't with the 6". I don't need to tell you how to make pistons LOL

I agree Piston Guy. I got a sample in, like Mark described, and the owner was telling me that his puke tank was working overtime. I believe that the other Piston makers were thickening the land to make it quit detonating from the extra oil that was getting by the ring pack. So I thinned up the lands just enough to get pin out of the 2nd land and that was the cure.

I meant third land.

I should try sleeping...like normal people.

piston guy wrote: ↑Wed Mar 25, 2020 11:39 am Mark ,
I have done it before using pin buttons . "I" don't like it because we try hard to keep oil from migrating above the oil ring and putting the pin above the oil ring provides a pathway for oil to go above the oil ring easily. If you went to a 1.2x1.2 top and second with a .250 down top ring , it would work. I did one that way "once". The rods bolts will hit the bottom of the bores too. They don't with the 6". I don't need to tell you how to make pistons LOL

On a Cleveland. That would leave .030 land in the valve relief in a world where everyone is a tuneup artist. I use a .043 .043 3.0 in that series. I'd guess I need .050, and I'm not getting it from the rings.

I figured the motor would be happier with a notch in the bottom of the cylinder and a piston that mostly is still in in there with it. I know I can do it with a keyed pin button....just didn't know if it would be an oil derrick without it. The few times I've done it, the oil was a secondary consideration.

Napier oil rings ARE magic, after all.....

I had it with a .250 land and .150 pocket. Unless the head is milled , that usually works. You might be dealing with with more duration than a 270@ .050 solid roller.

I use a standard relief of .220 and a top land .100 thicker than that.

Too much is not a problem, too little is a large problem. If it's a custom, that's a different story.

Mark, what is it you are seeing that is putting you off with the 4 inch stroke /6 inch rod deal in the 9.2 block apart from the obvious skirt issue?
Apart from some light scuffing of the pistons we’re not seeing much wrong. Granted, the amount of skirt protrusion isn’t ideal at BDC .

russxr67 wrote: ↑Thu Mar 26, 2020 6:06 pm Mark, what is it you are seeing that is putting you off with the 4 inch stroke /6 inch rod deal in the 9.2 block apart from the obvious skirt issue?
Apart from some light scuffing of the pistons we’re not seeing much wrong. Granted, the amount of skirt protrusion isn’t ideal at BDC .

That's it. It really bugs me to have the skirts get scuffed up like that. It has to eat some power if there is metal to metal contact there.

If you can get away with the .150 intake pocket, or use a keyed button (see below) , and stick a 6.125 rod in there......

Yeah, it’s not ideal, a fair bit of the piston skirt is exposed and it does leave some undesirable scuff marks but I’m not sure how it impacts the longevity of everything.
And yet on the 3.85 stroke combo’s I’m not seeing any scuffing at all.
I do , as a matter of diligence chamfer the bottom of the bores on all combinations though.

The 3.850 with a 6.125 rod was always my go-to combination for the Cleveland. I understand the desire for the 4.000 crank....but it's just bad physics.

I'm going to talk someone into that 4.000 stroke with a 6.125 rods and a 1.065 C/H. Every 347 on the planet (except BOSS blocks) has the cylinders notched for the rod bolt. That bothers me not one whit.

The best thing about this industry is being able to use your customers for engineering experiments......

bit confused is the pin portruding into the oil ring or the second compression ring?

Never had the pin bore into the second land, but every other build I've done except for stock or mild performance builds has had the pin in the oil ring lands. Never an issue with it either....I just use a spacer to bridge the gap.

Mark O, i like your humor......laughter is a good thing in this time of uncertainty. Mark H.