Wrist pin issue [Archive]

all-mtr-teg

10-09-2009, 11:05 PM

I took some New ITR pistons to get pressed onto some GSR rods and 1 wrist pin isn't centered. On one side, the wrist pin actually sticks out of the piston hole by about 1mm, while on the other end, it's about 5mm sunk into the piston hole. Will this have any harmful affects such as excessive piston skirt wear or anything else?

http://i255.photobucket.com/albums/hh135/all-mtr-teg/DSC02283.jpg

http://i255.photobucket.com/albums/hh135/all-mtr-teg/DSC02284.jpg

liveforphysics

10-09-2009, 11:15 PM

If it's really only 0.5mm x 1mm, it shouldn't matter.

That shows some poor attention to detail from the machine shop though, and attention to detail is critical for a machine shop. I wouldn't want a guy sizing my rod who doesn't pay attention to get pin height right.

Easy enough to take it back and say you want it centered, but for 1mm it would hardly be worth the effort.

all-mtr-teg

10-09-2009, 11:20 PM

Yeah, that's what I get for going to another shop instead of the guy I normally go to. I needed it done today so I can assemble the motor and return it to my buddy first thing Monday morning, but the machinist I normally use took his wife to a Doctor/Specialist and was out of town.

all-mtr-teg

10-09-2009, 11:22 PM

If it's really only 0.5mm x 1mm, it shouldn't matter.

No it's sticking out about 1mm on one side, and sunk in about 5.0mm on the other side.

DC_Legacy

10-09-2009, 11:24 PM

i'd take it back and have'em get it centered properly.

SOHCinWA

10-09-2009, 11:25 PM

I would have the shop that pressed them in look at it.. I know my guy looked at mine 2 years later and said..... "Holy shit! Who layed these pins in?" I said YOU DID!... He said it wasnt right.

You may want to have them check it.

all-mtr-teg

10-09-2009, 11:26 PM

Yeah, looks like homeboy is gonna have to wait until Tuesday to get his motor back.

all-mtr-teg

10-09-2009, 11:27 PM

Aquafina

10-10-2009, 12:27 AM

Did you have these done today (Friday, I'm still up)?

If so, wait to go back until Tuesday.

all-mtr-teg

10-10-2009, 12:45 AM

Yeah, I had these done this afternoon (Friday) but I didn't notice until I got home and started assembling the motor. By then, the shop was closed, (local Napa Machine Shop)
I'll take it back Monday morning before work and hopefully get the head back on it afterwork, and delivery it Tuesday morning.

liveforphysics

10-10-2009, 02:52 AM

If you're doing a stock rebuild of your 1985 dodge caravan engine, the local napa machine shop precision may be up to the task.

If you're building a precision performance engine, getting any and all machine/assembly done at a race engine build shop is very much worth the extra cost. It only takes one tiny detail over looked by the retard at Napa to cost you the entire engine (like an invisible stress crack in the piston from improper pin pressing for example, which happens).

Having an old man that gripes and bitches and costs a fortune put your engine together = win. Every town has one. Look for a wall of trophies to be in the shop entrance area before you drop your engine off. Doesn't make a difference what sort of racing the trophies are from.

all-mtr-teg

10-10-2009, 07:42 AM

Oh for sure, like I said, the machinist I normally use was out of town, and the owner of this motor wanted the motor back by Monday, so he asked me to take it to anyone. It's going in a daily driver, with bolts ons. But yeah, the guy I normally go to builds some serious motors. He and his son got several trophies and several drag cars.

Rocket

10-10-2009, 10:55 AM

Pressing off may distort the pin bore. A good shop will kiss it with a hone.

all-mtr-teg

10-10-2009, 06:35 PM

I took it to an old school builder, he heated up the rod end and lightly tapped the wrist pin with a smaller bore wrist pin and he managed to get it centered.

liveforphysics

10-10-2009, 07:21 PM

Out of curiosity, what did he heat the small end of the rod with that didn't heat the pin (if they both expand it does no good), and didn't cause localized piston heating (ruining the piston)?

I only ask because I've never found a good way to do it, and always end up having to press the pins out entirely, throw the rod small ends in the inductive heating coil, set the piston in the fixture, and put the pin in again to the correct depth.

But... Fortunately I rarely find myself bothering with non-floating rods anymore, so it's not too much of an issue for me :)

all-mtr-teg

10-10-2009, 08:25 PM

Not sure, I dropped it off to him and he called me up when he had it done.