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The open end of the wrist pin goes to the exhaust side?

Pin should be installed with it's closed end toward inlet port in cylinder.



*NOTE *
Interesting that two kinds of lock rings are used. Wire type rings are used in pistons with rounded lock groves. In pistons with square bottom groves, install flat locking ring with square-cut side of ring away from pin.

Thanks Rob.

Rob,

I always put the closed end on the exhaust side on 820's toward the exhaust like you suggested.

The 700 5-ports I'm working on now came with the open end towards the exhaust side. The engines had been raced many times and were built by a 700-580 guy in Ohio. All of the intake ports are opposite the exhaust. Do you suppose that the open wrist pin pointed towards the intakes would mess with the air flow?

I'm guessing that it probably doesn't make any difference but I will check with someone that has a service manual and see what the factory suggested.

Dick Teal

What I posted was out of a service manual. I didn't know anything about 2 styles of clips to hold wrist pin in place. That means pistons need certain clips to be correct & may cause damage if one was installed in the other piston.

I think they put closed end at intake to "stuff" the crankcase more but doubt it had any effect at all. It would only be "open" for a split second when piston was passing the port.

This is what Louie Figone sent me from his service manual.

Open end goes on the exhaust side. The book says "The closed end of piston
pin, anchor pins and match mark on rod must face up toward support plate.
Make sure that ends of piston rings do not cover anchor pins."

It is interesting that they call the ring pins "anchor pins"

This is how the engines I'm working on were set up.

Dick Teal

Dick- sounds like Louie's manual is describing a vertical engine- "closed end of wristpin faces UP towards support plate." That probably keeps the fuel mixture from collecting in the wristpin, weighing it down.
Bill