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#701
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Quote:
Since I like many here want to learn. Just what laws of physics does installing the piston with the offset reversed break? Stan
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Stan Weiss/World Wide Enterprises Offering Performance Software Since 1987 http://www.magneticlynx.com/carfor/carfor.htm David Vizard & Stan Weiss' IOP / Flow / Induction Optimization - Cam Selection Software http://www.magneticlynx.com/DV Download FREE 14 Trial IOP / Flow Software http://www.magneticlynx.com/DV/Flow_..._Day_Trial.php Pontiac Pump Gas List http://www.magneticlynx.com/carfor/pont_gas.htm Using PMD Block and Heads List http://www.magneticlynx.com/carfor/pont_pmd.htm |
#702
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That question has been answered at least three times now if I counted right.
Drop back a few pages and read my response and what I did to correct the issues after installing a set backwards (and the connecting rods were installed correctly BTW) and dealing with the drama that caused for 10,000 miles. If that's not good enough read the copy/pasted response from GTOFreek about why we do NOT install pistons that have offset pins in the wrong direction in these engines.....Cliff Out.....
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If you can read this, thank a teacher. If you can read this in English, thank a Veteran! https://cliffshighperformance.com/ 73 Ventura, SOLD 455, 3740lbs, 11.30's at 120mph, 1977 Pontiac Q-jet, HO intake, HEI, 10" converter, 3.42 gears, DOT's, 7.20's at 96mph and still WAY under the roll bar rule. Best ET to date 7.18 at 97MPH (1/8th mile), |
#703
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I would say that the piston installation didn't break any laws of physics. They are merely complying with the laws. The laws dictate that the pressures and angles act on the pistons in a certain manner. The engineers, that designed the pistons, understood this better than anyone in this discussion. They designed an offset to minimize unwanted movements of the pistons and maximize efficiency. Choosing to go against this is most likely causing the noises in this engine. But he wants to blame it on the moon, stars, and everything else. I say, GOOD LUCK!
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#704
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Quote:
Stan
__________________
Stan Weiss/World Wide Enterprises Offering Performance Software Since 1987 http://www.magneticlynx.com/carfor/carfor.htm David Vizard & Stan Weiss' IOP / Flow / Induction Optimization - Cam Selection Software http://www.magneticlynx.com/DV Download FREE 14 Trial IOP / Flow Software http://www.magneticlynx.com/DV/Flow_..._Day_Trial.php Pontiac Pump Gas List http://www.magneticlynx.com/carfor/pont_gas.htm Using PMD Block and Heads List http://www.magneticlynx.com/carfor/pont_pmd.htm |
#705
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I know that my dad owned a 1969 Chevy pickup. He had the engine rebuilt. The guy put the pistons in backward. Guess what, it had a strange knock. |
#706
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Quote:
Stan
__________________
Stan Weiss/World Wide Enterprises Offering Performance Software Since 1987 http://www.magneticlynx.com/carfor/carfor.htm David Vizard & Stan Weiss' IOP / Flow / Induction Optimization - Cam Selection Software http://www.magneticlynx.com/DV Download FREE 14 Trial IOP / Flow Software http://www.magneticlynx.com/DV/Flow_..._Day_Trial.php Pontiac Pump Gas List http://www.magneticlynx.com/carfor/pont_gas.htm Using PMD Block and Heads List http://www.magneticlynx.com/carfor/pont_pmd.htm |
#707
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As a spectator (or maybe in this case an observer of a spectacle), gtofreek's explanation of offset was the most helpful for me:
https://forums.maxperformanceinc.com...6&postcount=24 |
#708
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No, I'll order custom pistons with the offset. Then I'll install the backwards to break the laws of physics.
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#709
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Maybe someone who has worked on a SD 455 stock engine can confirm the information that I have that Pontiac used pistons with no offset.
Stan
__________________
Stan Weiss/World Wide Enterprises Offering Performance Software Since 1987 http://www.magneticlynx.com/carfor/carfor.htm David Vizard & Stan Weiss' IOP / Flow / Induction Optimization - Cam Selection Software http://www.magneticlynx.com/DV Download FREE 14 Trial IOP / Flow Software http://www.magneticlynx.com/DV/Flow_..._Day_Trial.php Pontiac Pump Gas List http://www.magneticlynx.com/carfor/pont_gas.htm Using PMD Block and Heads List http://www.magneticlynx.com/carfor/pont_pmd.htm |
#710
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Having 7 out of 8 backwards and who knows how many rods facing the WRONG direction is plain and simple FUBAR. We can continue these discussions and feed this thread for days, weeks, months and even years and NOTHING gets better until the fundamental issues that have been discovered here are corrected.
I certainly hope that the OP is getting all this down in my over 500 pages of notes, and plans on addressing the issues at some point. I've purchased and installed sets of pistons with zero offset. Most were the two valve releif variety so you had to pay close attention to how you hung them on the rods as the larger reliefs needed to end up under intake valves, the smaller ones under exhaust valves. At the sme time the flats of the rods end up running together and chamfered portions out agains the filet in the crankshaft. Not overly difficult but does require exact precision to get all eight in where they need to be. I suspect what happens with these Pontiac engines is that having #2 as the lead cylinder instead of #1 throws some folks off some and why we see this sort of thing happening more than it should. I seen some very well experience engine machinists and pretty smart folks mess that deal up and why I loved to see the aftermarket start offering affordable full floating forged rods. At least you didn't have to get the press out and collapse a few pistons when they got hung on the rods incorrectly........FWIW
__________________
If you can read this, thank a teacher. If you can read this in English, thank a Veteran! https://cliffshighperformance.com/ 73 Ventura, SOLD 455, 3740lbs, 11.30's at 120mph, 1977 Pontiac Q-jet, HO intake, HEI, 10" converter, 3.42 gears, DOT's, 7.20's at 96mph and still WAY under the roll bar rule. Best ET to date 7.18 at 97MPH (1/8th mile), |
#711
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"Maybe someone who has worked on a SD 455 stock engine can confirm the information that I have that Pontiac used pistons with no offset."
I've done a hand full of them and with my bad cases of CRS can't remember. I do remember that the original 455 SD pistons were forged, hung on pretty heavy forged rods, and small valve reliefs in the shape of a "trough" maybe, not four like most factory and aftermarket replacement type forgings used.......
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If you can read this, thank a teacher. If you can read this in English, thank a Veteran! https://cliffshighperformance.com/ 73 Ventura, SOLD 455, 3740lbs, 11.30's at 120mph, 1977 Pontiac Q-jet, HO intake, HEI, 10" converter, 3.42 gears, DOT's, 7.20's at 96mph and still WAY under the roll bar rule. Best ET to date 7.18 at 97MPH (1/8th mile), |
#712
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I'd agree with Cliff that the pistons had a trough, so thinking they were not off-set. Also seem to remember Pontiac had complaints about piston slap when cold on the SD Birds?
Also having CRS, I thought they did not have any off-set.
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John Wallace - johnta1 Pontiac Power RULES !!! www.wallaceracing.com Winner of Top Class at Pontiac Nationals, 2004 Cordova Winner of Quick 16 At Ames 2004 Pontiac Tripower Nats KRE's MR-1 - 1st 5 second Pontiac block ever! "Every man has a right to his own opinion, but no man has a right to be wrong in his facts." "People demand freedom of speech to make up for the freedom of thought which they avoid." – Socrates |
#713
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Quote:
Stan
__________________
Stan Weiss/World Wide Enterprises Offering Performance Software Since 1987 http://www.magneticlynx.com/carfor/carfor.htm David Vizard & Stan Weiss' IOP / Flow / Induction Optimization - Cam Selection Software http://www.magneticlynx.com/DV Download FREE 14 Trial IOP / Flow Software http://www.magneticlynx.com/DV/Flow_..._Day_Trial.php Pontiac Pump Gas List http://www.magneticlynx.com/carfor/pont_gas.htm Using PMD Block and Heads List http://www.magneticlynx.com/carfor/pont_pmd.htm |
#714
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That's a good question. Maybe they chose a standard offset that minimized piston rocking and thrust loads on the piston. Maybe it's the maximum that they could justify. Maybe it just works well for all. Maybe the guy was mental. LOL
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#715
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Pistons were mass produced, fixed offset makes sense. 455SD was already receiving extra attention because of the rods, 326 just needed a slug to fill a hole. |
#716
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In the beginning I had genuine concern but it has evaporated |
#717
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Some good reading about piston pin offset and overall piston design:
https://www.jepistons.com/je-auto-bl...haracteristics. https://courses.washington.edu/engr1...ylinder%20bore. https://www.quora.com/What-is-a-pist...20power%20loss. https://www.speed-talk.com/forum/viewtopic.php?t=20391 |
#718
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Something related to piston noise is being overlooked here I think.
Prior to the the first 400 motor in 67 Pontiac pistons where fully round and in my mind other the the issue of having the rods facing the wrong way on the crank if you had a piston in a motor the wrong way I don’t think you would hear much added noise when cold. Now let’s look at the 350s, 400s, 428s and the 455s with there inventive usage of a Cam ground piston. Now if you reversed these pistons, yes to me you would be in for a good amount of cold slap noise, and along with the noise comes ware. Just some food for thought here.
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Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs! And he was not talking about 1/8 or 1/4 mile ETs! 1) 1940s 100% silver 4 cup tea server set. Two dry rotted 14 x 10 Micky Thompson slicks. 1) un-mailed in gift coupon from a 1972 box of corn flakes. Two pairs of brown leather flip flops, never seen more then 2 mph. Education is what your left with once you forget things! |
#719
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Turn it up to 11 and rip the knob off!
Seriously tho, Stan keeps mentioning SD’s & custom piston having zero pin offset. Wouldn’t a turned around stock piston be different with the same amount of offset, just in the opposite direction? Thanks Murf |
#720
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Big stereo and loud pipes solves those problems. I think this might need both.
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