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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

Post by ptuomov » Tue Nov 26, 2019 10:16 am

Mark O'Neal wrote:
Sat Jun 30, 2018 9:50 pm
There 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 » Thu Nov 28, 2019 4:00 pm

.040 per side is our goal.

Rod manufacturers make this difficult.

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Re: Piston wrist pin length

Post by ptuomov » 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.

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Re: Piston wrist pin length

Post by Mark O'Neal » 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.

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Re: Piston wrist pin length

Post by ptuomov » Fri Nov 29, 2019 6:22 pm

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 » Sat Nov 30, 2019 1:47 am

So....definitely not a Ford.

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Re: Piston wrist pin length

Post by ptuomov » Sat Nov 30, 2019 1:32 pm

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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