Wrist pin bent
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Re: Wrist pin bent
Which begs the question...what is a reasonable compromise between a wall thickness for weight consideration vs stability? Let’s say tool steel that is 2.5” long and 7,000 RPM.
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Re: Wrist pin bent
I would be concerned about the shape of the piston and its integrity after a blow up.
I would replace them both just to be safe.If it hit the head with enough force to bend the pin what does that say about the integrity of the piston and ring land areas
I would replace them both just to be safe.If it hit the head with enough force to bend the pin what does that say about the integrity of the piston and ring land areas
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Re: Wrist pin bent
In a super stock car? .075 to .090 wall.
In a dirt modified? 150 to .180 wall.
With 65 lbs of boost? .990 diameter .225 wall
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Re: Wrist pin bent
A very well known engine builder and engine masters winner , just changed the wrist pin thickness and the engine made more power.......
Stephen Johnson #2162
Horace Johnson #2167
SS/D 427 Ford Fairlane NHRA-IHRA
Ex-Jim Van Cleve
1985 Mustang GT N/A 331
Horace Johnson #2167
SS/D 427 Ford Fairlane NHRA-IHRA
Ex-Jim Van Cleve
1985 Mustang GT N/A 331
Re: Wrist pin bent
Nearly every time unless you had a sufficiently thick pin before.JohnsnsFord2@aol.com wrote: ↑Thu Jul 12, 2018 3:32 am A very well known engine builder and engine masters winner , just changed the wrist pin thickness and the engine made more power.......
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Re: Wrist pin bent
Thicker
Stephen Johnson #2162
Horace Johnson #2167
SS/D 427 Ford Fairlane NHRA-IHRA
Ex-Jim Van Cleve
1985 Mustang GT N/A 331
Horace Johnson #2167
SS/D 427 Ford Fairlane NHRA-IHRA
Ex-Jim Van Cleve
1985 Mustang GT N/A 331
Re: Wrist pin bent
I was to get .110"” wall for my Super Stock build. When the pistons and pins arrived, there was .220” or .250” wall wrist pins. I called Gibtech and said “hey, this is a drag race engine, not a truck puller!” The laughed at their screw up and told me it would be 3 weeks on .110” or could get .160” now. Thinking things were moving along faster (will I ever learn?), I took the .160” x 2.500” pins. Of course more than 3 weeks have passed but I think I’m ok with it. I think there was a 6 gram weight penalty but my new pistons are considerably lighter and overall is lighter.JohnsnsFord2@aol.com wrote: ↑Thu Jul 12, 2018 3:32 am A very well known engine builder and engine masters winner , just changed the wrist pin thickness and the engine made more power.......
Last machine operation is in progress and hopefully done this week. Cam tunnel.
Car went to chassis shop yesterday so we could get the new bathtub oil pan to fit in the car.
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1970 AMC AMX - 390 4-speed
Advanced Clutches - Red Line Racing Cams
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Re: Wrist pin bent
DCal wrote: ↑Thu Jul 12, 2018 9:59 amNearly every time unless you had a sufficiently thick pin before.JohnsnsFord2@aol.com wrote: ↑Thu Jul 12, 2018 3:32 am A very well known engine builder and engine masters winner , just changed the wrist pin thickness and the engine made more power.......
Yes...but getting a customer to buy the correct pin, when the pistons come with "free" standard pins, has become a fool's errand.
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Re: Wrist pin bent
"I" think you did yourself a favor by using the .160 wall pin. I see pistons that have cracked on the inside where the "pin towers" flow into the under crown all the time. Aluminum cracks because it's flexing . Most often the pin flex is the cause and the piston flexes while trying o follow it. The stiffer pin reduces flex and increases piston life. Piston weight, RPM and horsepower ( to me) are the major factors that determine what wall thickness pin to use. The other obvious fact is if the pin is flexing , power is being lost due to higher energy absorption.
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Re: Wrist pin bent
^^^^ you are so right sir
Stephen Johnson #2162
Horace Johnson #2167
SS/D 427 Ford Fairlane NHRA-IHRA
Ex-Jim Van Cleve
1985 Mustang GT N/A 331
Horace Johnson #2167
SS/D 427 Ford Fairlane NHRA-IHRA
Ex-Jim Van Cleve
1985 Mustang GT N/A 331
Re: Wrist pin bent
When I was faced with the decision, my gut told me this was an area were lighter may not be such a good thing. So going to the thicker wall never bothered me. And I just looked at my notes. It’s .165” x 2.50”, not .160”.
My pistons are about 30 grams lighter than previous and the pins are about 5 grams heavier. Net -20 grams.
My pistons are about 30 grams lighter than previous and the pins are about 5 grams heavier. Net -20 grams.
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1970 AMC AMX - 390 4-speed
Advanced Clutches - Red Line Racing Cams
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Re: Wrist pin bent
Not knowing the weight of the piston and rod, I used a load of 3000 lbs on the wrist pin of various wall thicknesses.Mark O'Neal wrote: ↑Thu Jun 28, 2018 7:02 pmIn a super stock car? .075 to .090 wall.
In a dirt modified? 150 to .180 wall.
With 65 lbs of boost? .990 diameter .225 wall
The deflection or bending for each wall thickness is:
.090" =0.00065"
.180" =0.00043"
.225" =0.00037"
what is the pin to piston bore clearance?