Queston about wieseco pistons?

[ernstudet22]

I just finished rebuilding a 200 hp johnson crossflow. I used .044 over wieseco's. I just saw some posts yesterday about the ring locating pins falling out. Is this still a problem with these pistons? Is it more prone to happen with the higher reving mercury's vs. omc? Am I Screwed?
Not feeling so good all the sudden.

[Jay Smith]

The production Weisco pistons have a tendency to loose locater pins , that is a real life situation and a fact. Although failures are prone to the higher RPM, higher piston crown temped. engines. I have seen so many pistons locater pins fail I refuse to build any performance type engine ( 2.4 -2.5 liter ) without a top pin piston ( cast or forged ) , I refuse to put a known bad actor in an engine thats created SO many failures. I have had VERY good luck with the John Marles method of top pinning pistons and he has done HUNDREDS of pistons for me, converting your forged side pinned pistons to top and remove the likely hood of failure to less that 1 % using Marles..Cast pistons seems less likely to loose the dislodge the locater pins , it is an expantion rate issue between the two different metals ( the aluminum piston and the steel pin ) and cast seems to be more pin friendly BUT there have been HUNDREDS of failures with them ( cast ) also if they are used in the High Performance arena.. IMO the likely hood of your motor having a very long longevity is at best 50-50..

Sorry to hang this over your head BUT you asked....

Jay @ JSRE

[Markus]

I just finished rebuilding a 200 hp johnson crossflow. I used .044 over wieseco's. I just saw some posts yesterday about the ring locating pins falling out. Is this still a problem with these pistons? Is it more prone to happen with the higher reving mercury's vs. omc? Am I Screwed?

I had it happen to a Yamaha within 20 hours. The pistons were cut, though, which may have exacerbated the problem.

[TXOBTECH]

Very good advice Jay, you can take that to the bank! I have been burned several times in the past with weiscos in a v-6 merc (2.5) and have not used them in years.
I did use them alot back then in the crossflow's and did'nt have any problems, I think your chances are better, I think I would run them and not worry, JMO, Dan

[Jeff_G]

If your motor is a normal pleasure/fishing boat then just run the motor and don't worry. There are thousands of pistons out there running successfully in that application. In addition the X-flow OMC motors do run cooler than the Mercury.
If you are running on a performance boat I would change the pistons or at least get them top pinned. This is another case where the cast standard piston outshines the forged in normal pleasure boat use.
You have also run into another problem with the Weisco's. Oversize. You are basically stuck with the Weisco's from here on out as they use a oversize no one else uses. Your next option would be to re-sleeve or another block.

[Riverratt]

Most people do not top pin crossflow pistons because of the the way they are made. They would be much harder to do since they are not flat top.

[Capt.Insane-o]

*mumble-curse* wiseco's.. *mumble - curse* locating pins...*mumble curse*

I'm with Jay on this. Last fall I put together a motor as an experiment. Ran 12 gallons of gas through it, maybe 45 min. Tore down and all pins showed were on their way out. Granted this is a 9000+ rpm motor. I made two passes of a mile running it that hard.

I'm in firm belief if you set them in the sun on a hot day you can shake them out by hand, or if the ups truck has bad shocks on the way to your house they are probably already half way out. After US1 does his work they are a great piston.

[mindblock]

Would pulling the pins out and placing a dab of jbweld cure them? just a thought.


EDIT>..would locktight work better?

[Frank Molé]

Would pulling the pins out and placing a dab of jbweld cure them? just a thought.


EDIT>..would locktight work better?

no and no

[mindblock]

Guess will never know

[Jay Smith]

Locater pins should be installed with an interferance fit ( the hole is slightly smaller than the pin ) and must be either installed or pressed in with pressure OR by heating the parent metal ( alum. piston ) causing it to swell a bit or chill the pin ( carbon steel ) causing it to shrink a bit BUT they are ( or should be ) a fit such that they will be very resistant in coming out but guess what it ain't so.

BTW :There is no epoxy on the planet that I know of the is good for more than 660 degrees ( pyro putty ) the crown top of a piston can reach 1200 degrees NO epoxy is going to survive that heat..

my .02

[mindblock]

On skidoos I pulled them out with needle noses. You could be right mechine them 1/10000 larger..And side of pistion is not same heat as top.

[Jay Smith]

Guess I'll have to disagree, the top of the piston will transfer heat to the upper land.. How would in not less than 1/8" away from and open to full combustion temps.

FYI: the upper locater pin is exposed to full combustion temps all the time..

On another note : I guess I'm confused machine what larger? The pin or the parent metal ? The issue here is that if you were to make the pin fit tighter it will still through heat expantion rates being different ( alum parent metal and steel pin ) the pin is still coming out with the different expantion rates and the ring acting as a tweezer pulling the pin out, also the parent metal being very soft can only with stand so much pressure of an interferance pressed fit then it will split the parent metal or the pin will fail during instillation ...

BTW : This is nothing new and if your versed in High Performance 2 stroke Outboard engines it ia and has been an ongoing problem destroying many fine engines, this has been a chronic issue for years until Marles started top pinning and the OEM factory started top pinning..

my.02

[mindblock]

Heat hits sides after melt..Im right...in Percentage.

[Jay Smith]

THE Facts still are that side pinned pistons will and do fail and guess what the FIX has already evolved , in place and working fine, its called top pinning..

End of the story....