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Pistons installed backwards |
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Boris Badanov 
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Joined: Dec/14/2013 Location: NH USA Status: Offline Points: 4210 |
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 Posted: Jul/03/2015 at 1:14pm |
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You got the right idea, it's all about the best geometry at the time of peak pressure.
But the offset being reversed does not change displacement or effective stroke. Most performance pistons are neutral offset. This does cost you a tiny amount of displacement. More offset makes for more displacement, more cubic inches. Offset was originaly done to reduce noize. |
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Gremlin Dreams
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toolmanxiii
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Posted: Jul/06/2015 at 10:08am |
read line 2.. then 3 and 4 . first you say it has no effect then say you lose some with no offset . with the pin offset more to outside of the cylinder you get a bit more stroke as the centerline has changed. |
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71 360 Hornet sst 83 2wd 360/727 Eagle wagon (crashed)
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Boris Badanov
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Posted: Jul/06/2015 at 11:42am |
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Rod offset is NOT piston offset.
With a 401 the rod offset is .075~ from center line. Flip that rod and if it does not bind it will likely blow up under load. Rod offset is to or from the centerline of the crank pin oriented front to back. No American V8 that I have dealt with have a zero offset. Piston offset is right to left to keep the piston against the thrust side to reduce noise and wear. Two entirely different animals. What I said is that weather you offset the pin away from the thrust side or in the direction of it the change in displacement is the same. Reversing the piston does not change displacement. Those of us whom use a zero piston offset lose a tiny amount of displacement. "But the offset being reversed does not change displacement or effective stroke." 100% correct. |
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Gremlin Dreams
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dogbone
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Posted: Jul/06/2015 at 11:45am |
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I think the tightness was a stiff piston pin. Machine shop says they have it loosened up, we'll see. Turns smooth with crank only.
I think I'm going to go with cast iron. For the number of miles it will be driven they will likely work just fine.
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Boris Badanov
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Posted: Jul/06/2015 at 1:06pm |
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If you have a rod(s) in reversed it may bind.
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Gremlin Dreams
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toolmanxiii
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Posted: Jul/06/2015 at 2:44pm |
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I stand corrected. should have done more research .
http://homepages.cae.wisc.edu/~hessel/faqs/kiva4faqs/zpistnCalculationWAndWOWristpinOffset.html |
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71 360 Hornet sst 83 2wd 360/727 Eagle wagon (crashed)
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Boris Badanov
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Posted: Jul/06/2015 at 8:08pm |
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Nuts, we all do it :-)
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Gremlin Dreams
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Boris Badanov wrote: