Stuffing wrist pins

[OWENS1]

I am working on an engine for my stv. I want to get every little bit of power possible. Is it worth trying to stuff the wrist pins? What is the best material to use?

[Jay Smith]

Don't waste your time ! I've tried cork, deltron, teflon, and aluminum all comes looseand gets into the engine .. I have a set of encapsolated wrist pins that uses the base material and cannot come out and destroy your engine. I have them for standard Merc. length and Wizard length I install them in one outta 5 engines we build and have had zero issues.....Also ours average 20 grams lighter also than any OEM W.Pins....

1 281 576 5088 cst

Jay

[Bies]

Forgive my ignorance, what is stuffing the wrist pen?

[Mark Poole ModVP]

The wrist pins are hollow. Stuffing them eliminates the "wasted" volume inside of each crankcase.

[Bies]

Do you do that before balance?, And does less crankcase volume equal better power?

[Bies]

Also, isn't the hollow pin covred by the cylinder?, Seems to me more recipracative weight to stuff them?

[wrechin2]

Do you do that before balance?, And does less crankcase volume equal better power?

Less crankcase volume......The crankcase goes into a vacuum sooner because it has less volume to deplete. Allowing more air/fuel to be drawn in. Then due to less volume, the air/fuel charge is under more pressure, this increases velocity of the air/fuel charge. This means more fuel gets transfered which equals more power. Hope this helps...

[Bies]

Thanks, that's what I want to hear. So I guess this would help on my 10.5' C hydro, and the 14' D Runabout?

[Dave S]

Go bigger...... Runn a 44 cid on the C and a 90 on the D.:eek: Not good for class racing.:rolleyes:

[Bies]

Thanks, can I machine the piston?, I'm just a dumass in Ok. trying to to learn the tricks. Wish I new Quincy Welding!

[wrechin2]

Thanks, can I machine the piston?

More specific??? ON what engine and what are you looking to do?

[Bies]

Running a 40Hp Mercury/Mariner on the 14', have a Merc200 for the 10.5' hydro,
Would like to get a foot, or a yamato. Have deal with what I have.
The 40 seems to have a sheared key hopefully, or a reed. only turns freely about 90*
have not got into it yet. Santa had to buy alot this year, it's all about funds.

Local club wants me to race, just going to have fun and learn the set ups, then maybe? They have been very helpful, just like all you guys on SF.

[wrechin2]

Depends on what year they are as there are several variations of the 40HP........You have 2 types of fuel charge designs. A cross flow and looper engines. I am by no means sufficient on those smaller engines. I bet if you started a thread of you own asking questions about them, you will get some results. This has hi-jacked the original thread.

On a cross flow, all I can think of is squaring the booster port. I have never heard of anyone trying to add like finger ports. It could easily be done with a mill. There are 2 versions of the inline 4 and 6 cylinder engine pistons, a low dome and a high dome. If you had a low dome, you could put in a high dome and raise compression around 7 PSI (if I remember correctly) on those engines. Some of the real early 40's had the same bore and used the same pistons as the 4&6 in-lines. I know they don't respond well to porting changes on the inline 6 and 4.

The later 40's are looper and I imagine some stuff that can be done to it. Maybe porting changed, cleaning up the intake passages, ect.

Hope this helps.

[us1]

Also, isn't the hollow pin covred by the cylinder?, Seems to me more recipracative weight to stuff them?

One end of the pin crosses the transfer port and exposes the pin volume too the crankcase volume.

[Mark75H]

Running a 40Hp Mercury/Mariner on the 14', have a Merc200 for the 10.5' hydro,
Would like to get a foot, or a yamato. Have deal with what I have.
The 40 seems to have a sheared key hopefully, or a reed. only turns freely about 90*
have not got into it yet. Santa had to buy alot this year, it's all about funds.

Local club wants me to race, just going to have fun and learn the set ups, then maybe? They have been very helpful, just like all you guys on SF.

I think you'd get more out of blueprint matching all your reciprocating parts for lightest weight.

[tlwjkw]

One end of the pin crosses the transfer port and exposes the pin volume too the crankcase volume.

Thats why some of tha short BP mahle/pins were closed on one end.............

[OWENS1]

Seems like closing only one end still leaves the volume of the pin exposed to the crankcase, since it is below the ring.

[us1]

Seems like closing only one end still leaves the volume of the pin exposed to the crankcase, since it is below the ring.

The open end backs up against the cylinder wall and crosses no ports.