Piston pin offset "controversy"

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replicaracer43

replicaracer43

Grumpy Old Man
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Despite my best efforts to avoid all juvenile "clickbait" youtubers, "UTG"....I ran across Steve dulcich and David frieburger, do a little brief segment about the subject, and evidently, "UTG" or "uncle tony" had a video where he claims horsepower gains from swapping factory pistons from one bank to the other. They said the gain would be almost immeasurable, and challenged him to do a back to back test, which of course, he wouldn't do. I personally think it's a mute point, nobody builds engines with 45 year old pistons and worn bores, but the discussion is pretty interesting, what say all you guys?
 
I know it used to be a "thing" back in the day. When I had my 440 down, re-ring, it was recommended by several local San Diego "guru's" that I do so.
 
67Dart273 said:
I know it used to be a "thing" back in the day. When I had my 440 down, re-ring, it was recommended by several local San Diego "guru's" that I do so.
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I agree, it's been suggested in the mopar speed bibles as well, but has anyone shown actual proof or is it just a theory?
 
I am guessing it's something racers did. UTG is/may be doing it on street engine, that may not be ideal. If you are running it then tearing it down regularly like a racer there may be benefit. Isn't it something to do with getting the rotating assembly turning with less resistance = higher rpms? Uncle Tony thing is cheap and free speed secrets etc.
 
If there were horse power to be had, aftermarket pistons would have the piston offset in them too.
 
Are aftermarket piston centered? I never really noticed. I have an old set of TarW and I used KBs in build once.
 
Here's what I say. I've never done any type of testing. I've always heard that it frees up a tad power by reducing friction. A true performance piston has the pin centered anyway, so what's the big deal? Why would you waste time flipping an old cast piston around backwards?
 
Its the low/no budget racing mantra of UTG, that and he knows his viewrs will tear their 318s down and actually do it...:lol:
 
Yes Mopar race manuals suggested switching Pistons to opposite Banks but as previously stated offset Pistons are thing of the past so kind of a moot point. But that being said if I had a set of factory 340 pistons and was to reuse them I would reverse them.
 
I think this came about back in the day as "an old hot rodder trick". If you had factory domes you had to flip from bank to bank. If you had flat tops with no valve relief, you could theoretically just turn the piston around in the bore. But what if you had pressed pins? Just switch from side to side, i.e. 1 for 2, 3 for 4, etc. Just like the dome situation. Pistons had/have an offset pin to avoid alot of noise on cold start up. I did this with a stock bottom end 1973 318. I had enough other stuff done to it that I can't definitively say that it really did anything. The 302 heads, aluminum single plane, and the old school purple cam probably had more to do with it than the damn pistons turned around!
 
I was told it bumps the HP curve up a bit. So you likely lose a bit midrange
 
I can tell u guys that I have did this many times. They all seemed to go better than stock. My buddy had a recently reringed 340 that didn’t run the numbers he wanted. We tore the motor down. Didn’t see anything wrong. Reversed the pistons and she ran 2/10s faster in the quarter mile. I had a 67 Dart GT I put a 70 340 in. It had the 284/484 purple shaft with Rhiads lifters, LD340 intake, 750 Carter Competition carb, recurved distributor and Casler headers with 2 1/2 in exhaust. 727 with factory high stall and 3.55 gears. The pistons were swapped side to side. Drove it 120 miles to the track. First run was 13.9. Eventually got it down to 13.2. Kim
 
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oldkimmer said:
I can tell u guys that I have did this many times. They all seemed to go better than stock. My buddy had a recently reringed 340 that didn’t run the numbers he wanted. We tore the motor down. Didn’t see anything wrong. Reversed the pistons and she ran 2/10s faster in the quarter mile. I had a 67 Dart GT I put a 70 340 in. It had the 284/484 purple shaft with Rhiads lifters, LD340 intake, 750 Carter Competition carb, recurved distributor and Casler headers with 2 1/2 in exhaust. 727 with factory high stall and 3.55 gears. The pistons were swapped side to side. Drove it 120 miles to the track. First run was 13.9. Eventually got it down to 13.2. Kim
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That's what I've always heard and read. Never done it myself. But I've had some people I know swear by it back in my dirt track days. The drawback is, pistons with offset pins are stock cast pistons. If you're flippin um around, that's lookin for more power. Lookin for more power from a cast piston. Think about that.
 
Motor trend guys are watching his channel too.... LOL. And, Steve made a comment in UTG's latest video about it stating he loves UTG channel and it's all good, no bad blood.
As for me personally, I've not tried it. So I cannot speak personally about it.
 
Dartswinger70 said:
Its the low/no budget racing mantra of UTG, that and he knows his viewrs will tear their 318s down and actually do it...:lol:
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I'm all for low budget, makes a guy think for performance instead of throw $$$ and parts at a project till he hits his goal.
 
Why wouldn't aftermarket have the offset also?
They must fell it's not necessary, I imagine it might free up a tinny bit friction hp.
 
273 said:
Why wouldn't aftermarket have the offset also?
They must fell it's not necessary, I imagine it might free up a tinny bit friction hp.
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Most stock replacement pistons have offset pin holes. The direction they install unloads one side of the piston more to reduce any noise such as piston slap. It's when you reverse the pistons to throw the offset the "other way" that it unloads the piston and frees up a little HP. Centered pin holes achieve the same thing. All HP pistons such as hypers and forged have the pins centered...at least all that I am aware of.
 
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273 said:
Why wouldn't aftermarket have the offset also?
They must fell it's not necessary, I imagine it might free up a tinny bit friction hp.
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The best thing to do is, if you're in doubt, measure what you have. It's not hard to determine where the pin is located. You can do it easily with a pair of dial calipers.
 
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??
 
Did anyone besides Dodge Brothers offset wrist pins? The engine was engineered, built, and used in industrial application before Henry Fords automobile. Engines designed for longevity, not rapid rpm ramps. The offset changes angle of rod, forces between piston and crank throw. I dont fully understand the engineering. I know they would run forever.
 
If the aftermarket pistons have a notch in them so they can be installed a certain way (like the originals were) they probably have a offset. No notch, no offset. My thoughts.

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oldkimmer said:
I can tell u guys that I have did this many times. They all seemed to go better than stock. My buddy had a recently reringed 340 that didn’t run the numbers he wanted. We tore the motor down. Didn’t see anything wrong. Reversed the pistons and she ran 2/10s faster in the quarter mile. I had a 67 Dart GT I put a 70 340 in. It had the 284/484 purple shaft with Rhiads lifters, LD340 intake, 750 Carter Competition carb, recurved distributor and Casler headers with 2 1/2 in exhaust. 727 with factory high stall and 3.55 gears. The pistons were swapped side to side. Drove it 120 miles to the track. First run was 13.9. Eventually got it down to 13.2. Kim
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How dare you suggest that UT isn't a complete and utter moron! Don't you know the rules around here? lol..

My understanding is, like others have suggested, it's a low buck way to free some low end up by reduced friction. It's in the DC docs and not meant for all out racing but racing using factory parts. That's it. only reason for the offset is to reduce noise while the engine warms up.

If that's wrong, I'd love someone to "splain" it and do so without bashing anyone in the process... Good luck with that. Gauntlet thrown.... :)

I think the people (not you) who have the innate need to bash UT and others like him, hilarious. Really? they have nothing better to do than stir **** up? I feel sorry for them....

Again, this is isn't meant for you @oldkimmer, just those who can shut their flaps long enough to think about why they are butt hurt.... and show where on the doll UT hurt them...
 
273 said:
Why wouldn't aftermarket have the offset also?
They must fell it's not necessary, I imagine it might free up a tinny bit friction hp.
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People using aftermarket pistons aren't usually worried about a little piston slapping around at warm up.
 
Uncle Tony says a loose engine is a happy engine. From what I can tell from all this is, yes it said in the old performance books to switch pistons around. It seems to reduce friction. Is there power gain? unknown at this point. I seem to think it info from 50 years ago, the aftermarket has changed and technology and practices have changed. Is Tony incorrect? No, not if that info is in old books. Is there power gain? We won't know until Nicks garage jumps on board with his dyno...:)
 
Dartswinger70 said:
Uncle Tony says a loose engine is a happy engine. From what I can tell from all this is, yes it said in the old performance books to switch pistons around. It seems to reduce friction. Is there power gain? unknown at this point. I seem to think it info from 50 years ago, the aftermarket has changed and technology and practices have changed. Is Tony incorrect? No, not if that info is in old books. Is there power gain? We won't know until Nicks garage jumps on board with his dyno...:)
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huh? Because the info is in "old books" it doesn't apply? LOL... whoa boy...

Also, it's never been said to "add" power, only "free up" low end power. Balancing an engine was in the old books too. I guess we shouldn't do that either to "free up power".....
 
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