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Piston wrist pin length

General engine tech -- Drag Racing to Circle Track

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ptuomov
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Re: Piston wrist pin length

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Mark O'Neal wrote: Sat Jun 30, 2018 9:50 pmThere are countries that measure using the metric system...and there is a country that went to the moon, built the most powerful military in history, as well as the largest industrial base ever...... :P :P
Did the Chinese go to the moon yet? I thought they only had that military guidance satellite installed on the dark side of the moon just on the right orbit.

Here's another question relating to the pin-to-boss overlap. Does the rod small end to pin boss clearance need to be minimal for this kind of small overlaps to survive? My logic is that a lot of exposed pin between the rod small end and the piston pin boss lead to the pin bending and that can't be good with this little overlap between the pin and the pin boss.
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Re: Piston wrist pin length

Post by Mark O'Neal »

.040 per side is our goal.

Rod manufacturers make this difficult.
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Re: Piston wrist pin length

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Mark O'Neal wrote: Thu Nov 28, 2019 4:00 pm .040 per side is our goal. Rod manufacturers make this difficult.
This will get custom rods from a forging intended for 6.2" rods, so I assume we can get whatever small end width we want.
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Re: Piston wrist pin length

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ptuomov wrote: Fri Nov 29, 2019 7:48 am
Mark O'Neal wrote: Thu Nov 28, 2019 4:00 pm .040 per side is our goal. Rod manufacturers make this difficult.
This will get custom rods from a forging intended for 6.2" rods, so I assume we can get whatever small end width we want.
I've seen them from 1.000 to 1.060....so getting the pinboss span from your pistons guy wouldn't be a bad idea. And make sure to beam offset is correct.
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Re: Piston wrist pin length

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Mark O'Neal wrote: Fri Nov 29, 2019 6:10 pm
ptuomov wrote: Fri Nov 29, 2019 7:48 am
Mark O'Neal wrote: Thu Nov 28, 2019 4:00 pm .040 per side is our goal. Rod manufacturers make this difficult.
This will get custom rods from a forging intended for 6.2" rods, so I assume we can get whatever small end width we want.
I've seen them from 1.000 to 1.060....so getting the pinboss span from your pistons guy wouldn't be a bad idea. And make sure to beam offset is correct.
The rod big ends will be asymmetric but the plan is to have the rod bearing mid point under the beam centerline and the beam centerline exactly under the middle of the piston.
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Re: Piston wrist pin length

Post by Mark O'Neal »

So....definitely not a Ford.
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Re: Piston wrist pin length

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Mark O'Neal wrote: Sat Nov 30, 2019 1:47 am So....definitely not a Ford.
No, not a ford.

This is an old and obsolete Porsche V8 from a ‘87 928 S4.

Bore offset is 25mm, journal is 52mm, rod big ends are 27mm wide, stock rods were produced by cutting 2mm off from the one side of symmetric 29mm wide 944 rod. The rod beam is centered relative to the piston and the rod bearing in the front back direction. Stock PPF rods are very strong but also very heavy at 860g for 150mm rod.
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Re: Piston wrist pin length

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I believe I can help..

Think of it this way, logically...not some old outdated dictionary definition ..

Engines run on combustible fuel.

Motors run on electricity.

Thanks
Randy

Mark O'Neal wrote: Sun Jul 08, 2018 4:03 amThrice
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There is no logical reason to call an Engine a motor.
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Re: Piston wrist pin length

Post by Mark O'Neal »

GLHS60 wrote: Wed Dec 11, 2019 4:54 pm I believe I can help..

Think of it this way, logically...not some old outdated dictionary definition ..

Engines run on combustible fuel.

Motors run on electricity.

Thanks
Randy

Mark O'Neal wrote: Sun Jul 08, 2018 4:03 amThrice
www.dictionary.com

learn to speak English.
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Re: Piston wrist pin length

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Is this thread turning into a piston wrist pin length measuring contest?
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Re: Piston wrist pin length

Post by GLHS60 »

Sorry to derail, I was only joking with my old pal Mark.

He likes to use ancient words like thrice.

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ptuomov wrote: Sat Dec 14, 2019 2:16 pm Is this thread turning into a piston wrist pin length measuring contest?
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Re: Piston wrist pin length

Post by Mark O'Neal »

And Randy likes to cruise the lake in his engineboat.
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Re: Piston wrist pin length

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Image

Bless you my friend, you got me!!

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Re: Piston wrist pin length

Post by ptuomov »

Here's a custom 10mm piston mockup by Mahle and the pin bosses are similarly really skinny. The specified pin is built like a brick house, but it doesn't overlap too much with the pin bosses in the piston!

Photo:
MahleCustom.jpeg.jpg
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Re: Piston wrist pin length

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Another picture of 1987 vs 2020:
093410C2-CEC8-439B-A51C-13D690BC3BF6.jpeg
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