A piston question....
#1698002
11/12/14 11:16 AM
11/12/14 11:16 AM
|
Joined: May 2014
Posts: 503
Idaho
1320Dart
OP
mopar
|
OP
mopar
Joined: May 2014
Posts: 503
Idaho
|
A while back I talked to a guy at Diamond Pistons. For the life of me I can’t remember his name. Anyways, I got to talking to him about how the wrist pin is off center, away from the cam, in the Mopar pistons. A trick done a while back was, if your pistons had duel eyebrows, top and bottom. You could flip the piston around 180°. With the wrist-pin closer to the cam. That would put less side load on the pistons. It supposedly freed up some HP. But they would rattle a bit till it warmed up. He said with the piston technology today, they don’t do that anymore. They just center up the wrist-pin to the center of the piston and call it good. That’s all he would say about it.  So is that true? If there is less side load, why wouldn't you want to do that anymore? With technology or not. What does everyone else think? I’m hoping that someone else has heard of this trick before.  Thanks for playing 
Greg ----------------------------------------------------------------- Cost is irrelevant, making memories is far more valuable! 
|
|
|
Re: A piston question....
[Re: Monte_Smith]
#1698005
11/12/14 06:17 PM
11/12/14 06:17 PM
|
Joined: May 2014
Posts: 503
Idaho
1320Dart
OP
mopar
|
OP
mopar
Joined: May 2014
Posts: 503
Idaho
|
Quote:
Only reason that was ever done was to make factory engines quiet when they were cold. No performance advantage at all. If you wonder why some replacement pistons with no eyebrows have an arrow.....that's why, offset pin
Monte
That's depressing.
I for sure thought there must be something to it. I know a couple of S/ST guys who still do that today
Greg ----------------------------------------------------------------- Cost is irrelevant, making memories is far more valuable!
|
|
|
Re: A piston question....
[Re: 1320Dart]
#1698006
11/13/14 01:41 AM
11/13/14 01:41 AM
|
Joined: Aug 2003
Posts: 43,163
Bend,OR USA
Cab_Burge
I Win
|
I Win
Joined: Aug 2003
Posts: 43,163
Bend,OR USA
|
Sometimes old school habits, good or bad, die hard Todays hypertutic(SP?) pistons are ran with a lot less clearance than the OEM cast pistons did back in the day. That trick on flipping the wrist pin offset was worth around 8 HP (reduction in internal friction  )according to one of the old inside track information Mopar spnosored racers, that was a good, cheap, legal gain when you where basically looking for one or two HP I've seen that gain from using Pro Blend on a 500 HP motor, which is right at 1.7 % gain
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
|
|
|
Re: A piston question....
[Re: 1320Dart]
#1698008
11/13/14 11:20 AM
11/13/14 11:20 AM
|
Joined: Jan 2003
Posts: 75,005
U.S.S.A.
JohnRR
I Win
|
I Win
Joined: Jan 2003
Posts: 75,005
U.S.S.A.
|
Quote:
Quote:
Sometimes old school habits, good or bad, die hard Todays hypertutic(SP?) pistons are ran with a lot less clearance than the OEM cast pistons did back in the day. That trick on flipping the wrist pin offset was worth around 8 HP (reduction in internal friction )according to one of the old inside track information Mopar spnosored racers, that was a good, cheap, legal gain when you where basically looking for one or two HP I've seen that gain from using Pro Blend on a 500 HP motor, which is right at 1.7 % gain
Hi Cab!!!! 
Pro Blend?
So if a person was to order pistons, it would be worth having the pin offset towards the cam?
you might be missing the point , offsetting the pin in the offset direction was an HP gain because of the negative effect of it being in the opposite direction.
Do you really think the technology has gone backwards in the past 2 or 3 decades ???
|
|
|
Re: A piston question....
[Re: JohnRR]
#1698010
11/13/14 12:51 PM
11/13/14 12:51 PM
|
Joined: May 2014
Posts: 503
Idaho
1320Dart
OP
mopar
|
OP
mopar
Joined: May 2014
Posts: 503
Idaho
|
Quote:
Quote:
Quote:
Sometimes old school habits, good or bad, die hard Todays hypertutic(SP?) pistons are ran with a lot less clearance than the OEM cast pistons did back in the day. That trick on flipping the wrist pin offset was worth around 8 HP (reduction in internal friction )according to one of the old inside track information Mopar spnosored racers, that was a good, cheap, legal gain when you where basically looking for one or two HP I've seen that gain from using Pro Blend on a 500 HP motor, which is right at 1.7 % gain
Hi Cab!!!!
Pro Blend?
So if a person was to order pistons, it would be worth having the pin offset towards the cam?
you might be missing the point , offsetting the pin in the offset direction was an HP gain because of the negative effect of it being in the opposite direction.
Do you really think the technology has gone backwards in the past 2 or 3 decades ???
"Do you really think the technology has gone backwards in the past 2 or 3 decades ???"
That's kind of a loaded question. We really haven't progressed all that much in engine technology since the late 50's. In the main mechanical design. Other than roller bearings on everything
Free HP is free HP. No matter how you look at it. So reducing friction or side load, for a 1.7% gain. I'm not sure if piston technology/design has improved that much in 2 decades .
Other than the piston coatings that help reduce friction and heat.
Greg ----------------------------------------------------------------- Cost is irrelevant, making memories is far more valuable!
|
|
|
Re: A piston question....
[Re: 1320Dart]
#1698011
11/13/14 02:39 PM
11/13/14 02:39 PM
|
Joined: Jan 2003
Posts: 75,005
U.S.S.A.
JohnRR
I Win
|
I Win
Joined: Jan 2003
Posts: 75,005
U.S.S.A.
|
I can't see the pistons makers taking out the offset if there was power to be gained with it being offset ??? The 1.7% gain to me seems mostly from the removed negative effect of it being offset? I unfortunately can't ask Dan  for his opinion on this.
|
|
|
Re: A piston question....
[Re: JohnRR]
#1698012
11/13/14 02:44 PM
11/13/14 02:44 PM
|
Joined: May 2014
Posts: 503
Idaho
1320Dart
OP
mopar
|
OP
mopar
Joined: May 2014
Posts: 503
Idaho
|
 I wish I could have met him. I became a member on here just prior to him getting sick. I have read quite a few of his posts though. Smart dude.
Greg ----------------------------------------------------------------- Cost is irrelevant, making memories is far more valuable!
|
|
|
Re: A piston question....
[Re: lewtot184]
#1698014
11/13/14 04:45 PM
11/13/14 04:45 PM
|
Joined: Jan 2005
Posts: 12,419
Kalispell Mt.
HotRodDave
I Live Here
|
I Live Here
Joined: Jan 2005
Posts: 12,419
Kalispell Mt.
|
Quote:
Quote:
Only reason that was ever done was to make factory engines quiet when they were cold. No performance advantage at all. If you wonder why some replacement pistons with no eyebrows have an arrow.....that's why, offset pin
Monte
this is why pistons had/have an offset. pistons with the offset were put in "backwards" to reduce friction. and some thought back in the day, and i was there, it helped rod angularity. if i remember correctly, back in the '60's, there was a hemi race piston that had the .060" offset in the opposite direction of a stock driver type piston.
hypereutectic pistons are not run tighter than production type cast pistons. they are ran .001-.002" looser. they don't have the thermal control that a cast steel struted/slotted oil ring groove production piston has.
i don't believe the aftermarket piston with the straight pin is any kind of "special speed secret". it's just an easy/straight forward way of doing business, but does have the benefit of reducing frictional loses at the expense of noise.
They actually are made to run tighter than the old cast piston with steel strut. The high silicon alloy does not expand nearly as much as the old cast ones and they expanded less than the old forged stuff. Modern OEM manufacturers are pretty much all using a high silicon alloy with very low expansion, no steel strut and very tight clearances. It gives lower emissions especially when cold, lower oil contamination, less friction because the alloy is slicker and harder, less noise, and less heat conducted away by the piston.
Piston tech has come a long ways in the last 30 years, don't believe me put a 340 piston and 6.4 hemi piston next to each other, the technology packed in that little hockey puck is glaring obvious
I am not causing global warming, I am just trying to hold off a impending Ice Age!
|
|
|
Re: A piston question....
[Re: HotRodDave]
#1698015
11/13/14 05:36 PM
11/13/14 05:36 PM
|
Joined: Jun 2008
Posts: 3,916
usa
lewtot184
master
|
master
Joined: Jun 2008
Posts: 3,916
usa
|
Quote:
Quote:
Quote:
Only reason that was ever done was to make factory engines quiet when they were cold. No performance advantage at all. If you wonder why some replacement pistons with no eyebrows have an arrow.....that's why, offset pin
Monte
this is why pistons had/have an offset. pistons with the offset were put in "backwards" to reduce friction. and some thought back in the day, and i was there, it helped rod angularity. if i remember correctly, back in the '60's, there was a hemi race piston that had the .060" offset in the opposite direction of a stock driver type piston.
hypereutectic pistons are not run tighter than production type cast pistons. they are ran .001-.002" looser. they don't have the thermal control that a cast steel struted/slotted oil ring groove production piston has.
i don't believe the aftermarket piston with the straight pin is any kind of "special speed secret". it's just an easy/straight forward way of doing business, but does have the benefit of reducing frictional loses at the expense of noise.
They actually are made to run tighter than the old cast piston with steel strut. The high silicon alloy does not expand nearly as much as the old cast ones and they expanded less than the old forged stuff. Modern OEM manufacturers are pretty much all using a high silicon alloy with very low expansion, no steel strut and very tight clearances. It gives lower emissions especially when cold, lower oil contamination, less friction because the alloy is slicker and harder, less noise, and less heat conducted away by the piston.
Piston tech has come a long ways in the last 30 years, don't believe me put a 340 piston and 6.4 hemi piston next to each other, the technology packed in that little hockey puck is glaring obvious
i don't agree with you on the hypereutectics. the old cast piston with the steel strut and slotted oil ring groove was to reduce expansion. the newer hypereutectics have the solid oil ring groove and no struts and transfer heat to the skirt.
|
|
|
|
|
