wrist pin under running conditions

[WATERWINGS]

If you heat a piston to get the wrist pin out, what happens when it is running, is it loose in it's hole?

And if it is then is it moving (or spinning) while running?

[WATERWINGS]

ttt

[Jay Smith]

TEST

[Jay Smith]

Waterwings,

I don't heat pistons to get the pins out my guy made me a cool piston stand that is concaved to accept a piston and has a hole bored in the bottom I use a 12 ton press the pin is pressed through the hole and clears the piston and the table.......

There are 2 reasons , to my knowlege, beyond lack of lubrication and heat that will cause a W.P. to be stubborn about coming out :

1. The W.P. bosses due to movement has become not aligned from one side to another and thrown the two mating bores of the W.P. bosses out of line bore.

2. If a pin is loose it will beat the cir clip into its relief boss and create a build up of material this causing the W.P. to not have enough clearence to be removed without a press or a punch and a 3 # hammer.....

I use a cartridge roll of very light grit grade ( 400 ) and dress up the edeges of the groove cut for the cir clip to seat in. I also use a 1/4" drill rod with a split in the end and roll up a piece of crockas cloth and polish this area.

If a wrist pin is properly fit I see no reason that it should move in anyway after all the rod is moving on it with a needle bearing fit and unless something goes a stray the least resistance would be for the rod to spin on the W.P. not the W.P. to spin or mnove in the tight fit piston boss........

My experiences.........

[WATERWINGS]

Hey Jay,

I thought the book calls for heating up the piston to remove the WP, Thats why I do it that way.

I worried that driving them out might damage the bore of the WP.

When I put a little heat on the under side of the piston, the WP almost falls out.

But I was wondering if under running conditions (with the heat of running) if the WP would be loose as if heated by torch?

Thanks,


John

[T-REX]

Under running contitions, upon reaching operating temp, the wristpin and the piston are basically the same heet, thus expanding the same amount, keeping the tolerances az when kool...now if U start ya engine, bust it in tha ass before warm up, the aluminium piston will expand befor the WP, thus give'in ya a lil more slop till the WP kan catch up...When U don't let a motor warm up, this WP slop can kick out a WP keeper...Warm up iz a very critical part ov a internal combustion engine, no mater what kind it iz...ever type of metal in yo motor expands and contracts at a diffrent rate and with a diffren amount ov heet...when ya stop and think about what takes place in tha first cold start up till operatein temp, U won't have any problem lett'in her warm up!!!REX:cool:

[Jay Smith]

I agree with T-Rex ( now ain't that scary ) but one has to relilize that the wrist pin is on the"cold" side of the piston which is getting cooled by the oncoming fuel /oil vapor. This side is always being cooled , an extreme heat source can't be under the crown or an intercrankcase explosing would occure. As the heat would light off the incoming vapor and blow the reeds clean out the front of the motor..........

[Raceman]

"Under running contitions, upon reaching operating temp, the wristpin and the piston are basically the same heat, thus expanding the same amount, "

Whoah there boyz. With alum having a much different expansion coefficient than steel, how'z the clearance gonna remain the same when they're up to temperature?

[T-REX]

Az Jay said in hiz reply, the wristpin iz actually cooler than the piston, and to git to a natz ass, the further down on the piston, the cooler it iz...U are right about the expansion charataristikz ov aluminium vs steel...but, diffrent steels and diffrent aluminiums also have diffrent expansion charataristikz...The crown of the piston will be by far the hotest part, with the heet transferein downward...thus the incoming fuel in the crank case iz cooler and tends to cool the underside of the piston and WP...Have U by chance noticed the diffrence in the way a forged piston and a cast piston recieve a WP???...The cast piston will not have the same expansion az the cast one...But when all iz said and dun, and the engine iz at operating temp, the internal parts are operating at thier intended specs, unless other wise screwed wit by sumone like me!!!...What I'm trying to say, iz at operating temp, the clearences are where they iz pozed to be...They call this a engineering feature...A lil bit ov engineering went into the joining of steel and aluminium...it didn't juss happen...Heet variations have a drastik impact on the clearances in a 2 stroke(az also 4strokes)...Now, Raceman, U muss be bored ta hit me wit dat off tha wall bull****....U better git out to da shop and polish sum ov them super HP build'in Tuners U got...Does tha expansion ov a tuner have an affect on it's advertized performance????....See, dat **** workz 2 wayz...Glad ta see ya still wit us...REX

[RichS]

Hey WW, I think you got the idea. And that is why there is also oiling holes and grooves in the pin holes in those pistons. And if you use a duburr knife on the clip groove burr before you push the pin out you can just push them out by hand, cold.

[Raceman]

Well Rex, here's what I'z 'spicious of. Them engineers is smart enough to figure how much clearance they gotta build in them components cold to make em have tha desired clearance hot, but you ain't gonna make me bleeve them two numbers is tha same.

Now as far as expansion co-efficients of them tuners, I think they'ze di-rectly pro-portional to the con-traction co-efficent of tha people that buy's em's wallets. 'Course both of these numbers have a direct parabolic effect on tha bank accounts of tha vendors that're suckerin' all these folks into buying these aftermarket tuners in tha first place.

[Skeet]

I always nearbout kinda figgerd o TRex was always smokin sompin, but dammmit boy if ol Raceman ain't smokin da same chit.

And da Raceman stay jes rat down daroad from me for a lil waaz.

Raceman, got the coordinates for yo place? Next time I'm at Sinclair I might jes drop on in.....Mr Jones tolt me you had an impressive setup.

Skeet

[Raceman]

Skeet, not to change the subject or anything, but are you into cars too? I was just wondering when/if the monthly cruise is gonna get goin' again at Tanger.

[QUICKSILVER]

Merc manual says to warm the piston using a torch lamp to ease pin removal. It shows someone holding the piston while removing the wrist pin. I don't think it would be very hot. Some of the early V6 manuals (for the 3 ring piston motors) said to heat the piston to remove the wrist pin and not to reuse the pistons if the wrist pins had been removed. I use a block, like Jay described. They always press right out.

[Skeet]

Raceman,

I don't have enough seniority to get into hotrod cars yet. Its coming one day though. I have a couple of friends who are into it big time. One is restoring an old Biscayne from top to bottom. He just has the frame sitting in his shop right now with the steering brakes tires...and da drivetrain. A big O Rat modah, all clean and shiny.

When I drop in on him we don't do nothing but look at it and tell lies.....

Not sure when that Tanger thang is happenin again.

Skeet

[Raceman]

Skeet, a buddy told me last night that it's definately kickin' off again the first Saturday afternoon in April and runnin' til October. I might drag the yellow STV up just to give the guys something different to look at.

[T-REX]

Last yeer I called a buddie ov mine(he runs the golden oldies car shows) and ask him about bringin my lil boat...I then called a couple ov guyz wit botes and we showed up at the show...we had the whole show covered...I pulled my lil rex wit my ole wagon and took the audience popularity award...Not to mention tha best look'in driver there;) ...I want to put together a couple Saturday evening for just a boating git together like a cruise night...Jus fir ****z and giggles...Tow that STV wit da Viper and blow thier sockz off...REX:cool:

[CrayzKirk]

Here is my take on this... (guess only)...

The aluminum will expand more than the steel and at a lower temperature. I figured the pins floated in the bore. There are holes and channels for gas/oil to flow and that should fill the areas between the parts and cool both parts.

Without oil, all parts of the engine would heat rapidly and fail.

By the way, how long do you warm them up before hitting it?

Kirk

[Cycix]

The coefficient of thermal expansion for cast iron is 0.0000061, for aluminum it is 0.0000128 or twice as much, I don't think it's a very considerable amount difference for cast metals. The equasion to figure it is
LenthofIncrease = Coeff.*ChangeIntemp*OrigionalLenght

The orgional length "OrigionalLenth" in this case would be the Pi*Diameter of the hole / wrist pin. Than you could figure the difference by subtracting the two. Hope that helps.

[Skeet]

Raceman,

When you come up to Tanger let me and Dynobo know so we can come check out your ride and float. After you through impressing all dem rednecks we can go over to Bobo's shop and put your motor on the dyno if ya want. His shop ain't but a mile from Tanger.

Skeet

[Raceman]

There's a propshaft dyno in Hampton? Here's a dumb question, since I don't have much propshaft dyno experience: Does it care which way the shaft turns? This one's a leftie.

[Skeet]

Raceman,

Dynobo has made several posts here. He's the one with the LandnSea propshaft dyno. It was setup here at my house in Hampton for a while, he just picked it up to setup at his new shop in Locust Grove.

I'm pretty sure it will work on a lefty because the torque arm has rubber bumpers for either side of the cavitation plate. Where does your motor take in its cooling water.....or how do you hook up a hose when you run it on the trailer? Seems like I read you had one of those funkadelic forward only gearcases.

Skeet

[Raceman]

Skeet, I've got a boat ramp at my lakehouse, so I always back the boat in deep enough to crank it and don't ever just run it on the trailer. I've got a Speedmaster type flush attachment somewhere to run on the hose, but haven't ever used it. I guess I'll try to dig it out.