Piston pin offset "controversy"

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318willrun said:
actually, UTG said he'd like to do it at the track. Make a couple passes, tear down, reverse the pistons, re-assemble, and make more passes on the same day with the same engine. He did say if MT would pay for it, he would perhaps be interested in bringing the gaskets and crew to get it all done. I think that's fair....
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Crew? He doesn't have very good luck with engines and his crew! :poke::rofl:
 
dirty white boy said:
it not the one thing that make a better engine,..its all the lil things that add up! this is just a way to free up a lil drag! but who's trying build power with badger replacement pistons??
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Exactly. Someone gets my point! LOL

I can tell you who in the past, though. Remember the "Bomber" dirt track class? I don't know how it was in other parts of the country, but down here, that class was strictly stock. I've known some guys that did it then....and as long as they stayed outta the wall, they did pretty good. I was in it for a short time too. Me and a friend were directly responsible for the duration rule change in that class, because all they used to measure was lift and we used a cheater cam for several races. They didn't like that chit so they moved the goal posts.
 
Cuda416 said:
People using aftermarket pistons aren't usually worried about a little piston slapping around at warm up.
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Piston slap never bothers me in a real high performance engine. Because a real high performance engine uses a forged piston and you're gonna have to almost be swappin holes to crack one of those. They can take a lot of clearance before you have to worry about breaking one from piston slap. I ran a Chevy 350 at a slap wore out .060 over with the old TRW 12:1 heavy *** domed pistons with open chamber heads and a big lumpy cam. It had between .008 and .011 piston to wall. LOL But that was one STRONG stock stroke engine. Sounded like a Cummins when it busted off cold but when it got warm you almost couldn't hear it. Almost. lol
 
RustyRatRod said:
Piston slap never bothers me in a real high performance engine. Because a real high performance engine uses a forged piston and you're gonna have to almost be swappin holes to crack one of those. They can take a lot of clearance before you have to worry about breaking one from piston slap. I ran a Chevy 350 at a slap wore out .060 over with the old TRW 12:1 heavy *** domed pistons with open chamber heads and a big lumpy cam. It had between .008 and .011 piston to wall. LOL But that was one STRONG stock stroke engine. Sounded like a Cummins when it busted off cold but when it got warm you almost couldn't hear it. Almost. lol
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Yessir, exactly my point.
 
toolmanmike said:
The factory performance guys figured it out. It was in the Mopar performance books written by them. (and not Hot Rod Magazine) so I doubt is was a myth. It needs to be proven but like I said above, finding the right engine with the factory pistons in it would be next to impossible.
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I have HP 273's and 340's that will go back together after a hone. I'll swap pistons side to side. Those old guys knew what they were doing. Every time I tried what they recommended it worked out fine. But I won't do it both ways, like said previously, it's not one thing, but everything you do.
 
1st it ant gonna make more hp, its just gonna free up lost hp, but this alone probably wouldnt be enuff to notice on a dyno! its basic physics not rocket surgery!! swear some of yall would argue just for the sake of arguing, like mudd wrassling pigs, sooner or later ya realize the pigs enjoy it!!
 
RustyRatRod said:
Piston slap never bothers me in a real high performance engine. Because a real high performance engine uses a forged piston and you're gonna have to almost be swappin holes to crack one of those. They can take a lot of clearance before you have to worry about breaking one from piston slap. I ran a Chevy 350 at a slap wore out .060 over with the old TRW 12:1 heavy *** domed pistons with open chamber heads and a big lumpy cam. It had between .008 and .011 piston to wall. LOL But that was one STRONG stock stroke engine. Sounded like a Cummins when it busted off cold but when it got warm you almost couldn't hear it. Almost. lol
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I had a 350 with the high domes when I was young and it was 7 to 10 thou slop in the holes. That thing would scream.
 
Although it's true that modern lightweight forgings have the pin centered , it's not just cast pistons that have the pin offset. I think pretty much all the "classic" TRW/ Speed pro forged pistons (2355,2295 etc.) have the pin offset. I read an article in which David Vizard claimed there were benefits to reversing the pin offset and conducted a dyno test showing some gains. I can't remember the details and I'm off to search the "net for the answer.:steering:
 
318willrun said:
actually, UTG said he'd like to do it at the track. Make a couple passes, tear down, reverse the pistons, re-assemble, and make more passes on the same day with the same engine. He did say if MT would pay for it, he would perhaps be interested in bringing the gaskets and crew to get it all done. I think that's fair....
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The gain is so little there is no way on earth he could swap that crap out at the track and use the time slip as a verification. That’s what a dyno is for.

And, if there was ANY power outside of margin of error, modern pistons would be offset and they would instruct you to flip them.

The fact of the matter is current pistons are so far superior to any of the older OE stuff it’s not funny. Today, we don’t have to use obsolete OE pistons and such, with horrible ring packs.

In fact, I will say unequivocally that there is far more horsepower in thinner ring packs than there ever was or could be by swapping offset pin pistons around.

It’s as simple as that.
 
yellow rose said:
The gain is so little there is no way on earth he could swap that crap out at the track and use the time slip as a verification. That’s what a dyno is for.

And, if there was ANY power outside of margin of error, modern pistons would be offset and they would instruct you to flip them.

The fact of the matter is current pistons are so far superior to any of the older OE stuff it’s not funny. Today, we don’t have to use obsolete OE pistons and such, with horrible ring packs.

In fact, I will say unequivocally that there is far more horsepower in thinner ring packs than there ever was or could be by swapping offset pin pistons around.

It’s as simple as that.
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Yup. Ring friction is the number one friction in an engine and anything you can do to reduce it flat out works. I try to find low tension rings for everything.....course for a slant, that's kinda tough. lol But I'm considering the Weisco pistons for the next build. They have a very modern ring pack. Nice and thin.
 
yellow rose said:
The gain is so little there is no way on earth he could swap that crap out at the track and use the time slip as a verification. That’s what a dyno is for.

And, if there was ANY power outside of margin of error, modern pistons would be offset and they would instruct you to flip them.

The fact of the matter is current pistons are so far superior to any of the older OE stuff it’s not funny. Today, we don’t have to use obsolete OE pistons and such, with horrible ring packs.

In fact, I will say unequivocally that there is far more horsepower in thinner ring packs than there ever was or could be by swapping offset pin pistons around.

It’s as simple as that.
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New pistons are not the discussion. Superior parts are not the discussion. What’s being discussed is if you swapped OE pistons from bank to bank, would there be a gain. It’s as simple as that. Not my claims or argument. I’ve not tried it.
 
318willrun said:
New pistons are not the discussion. Superior parts are not the discussion. What’s being discussed is if you swapped OE pistons from bank to bank, would there be a gain. It’s as simple as that.
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And I, suggesting rather than spending money swapping obsolete junk around to save some money and buy a good piston. The rings eat up way more power, by FAR than the off center pin does.

Living in the 1970’s for more than about 5 minutes of reliving your salad days is a waste of time. And money.
 
yellow rose said:
And I, suggesting rather than spending money swapping obsolete junk around to save some money and buy a good piston. The rings eat up way more power, by FAR than the off center pin does.

Living in the 1970’s for more than about 5 minutes of reliving your salad days is a waste of time. And money.
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I hear ya, and you can take that point of view to UTG and the MT guys. Their arguments and their claims
 
318willrun said:
I hear ya, and you can take that point of view to UTG and the MT guys. Their arguments and their claims
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I can one up you. Just as a rough guess, how many guys today do you think dyno their engines today? I’m betting it’s way under 10% and there are a ton more dyno’s out there today then there was when those books were written.

Just as a rough guess, how many guys today do you think actually can test at the track and do it even remotely accurately? i suggest that I’ve been to the track enough times with guys to help them and maybe 1% of the time they make 3 good enough passes to assess a single change. I’ve seen guys who couldn’t do the same thing twice in a row. So how do you evaluate that?

So put the two together. Back in “the day”, those guys didn’t use a dyno. Most of them didn’t test, and if they did, they didn’t do it well. So taking what those guys did back then has to be taken with a 10 pound bag of salt.

BTW, they shouldn’t have any argument about rings and horsepower. That’s been proven so many times it’s silly to even dispute the fact.
 
yellow rose said:
I can one up you. Just as a rough guess, how many guys today do you think dyno their engines today? I’m betting it’s way under 10% and there are a ton more dyno’s out there today then there was when those books were written.

Just as a rough guess, how many guys today do you think actually can test at the track and do it even remotely accurately? i suggest that I’ve been to the track enough times with guys to help them and maybe 1% of the time they make 3 good enough passes to assess a single change. I’ve seen guys who couldn’t do the same thing twice in a row. So how do you evaluate that?

So put the two together. Back in “the day”, those guys didn’t use a dyno. Most of them didn’t test, and if they did, they didn’t do it well. So taking what those guys did back then has to be taken with a 10 pound bag of salt.

BTW, they shouldn’t have any argument about rings and horsepower. That’s been proven so many times it’s silly to even dispute the fact.
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Probably true. I’ve not instructed anyone ever to swap banks
 
318willrun said:
New pistons are not the discussion. Superior parts are not the discussion. What’s being discussed is if you swapped OE pistons from bank to bank, would there be a gain. It’s as simple as that. Not my claims or argument. I’ve not tried it.
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I think there must be, or else the rumor wouldn't persist so.
 
318willrun said:
Probably true. I’ve not instructed anyone ever to swap banks
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Some day you should take a couple guys to the track and tell them you want to test something. Then take notes. See if they can do a burnout the same twice in a row. Maybe, but doubtful.

On board data logging showed how horrible some drivers are. I’ve seen guys that would shift at 7800 one run and 7200 the next run and they never changed the shift light. They said I was lying until I showed them their own logs.

Foot brake guys can be off 200-250 RPM at the launch and not even know it. Clutch guys...I won’t even go there. They are mostly bad. 500 RPM launch RPM changes is typical.

You can’t test with numbers like that, but many guys claim they do. That’s why I’m skeptical of at the track testing of engine changes, especially when you are talking low power increases.

Hence, why I can’t say that swapping pistons bank to bank will save any power. I’ve never seen it tested. When one of the big spenders around here gets one together and wants to test it, I’ll give them up to 2 days on the dyno for FREE to flog it and see what’s there. But I damn sure wouldn’t try it at the track. I don’t hate myself that much.
 
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