Piston Pin contact area damaged??

NoEardGoat · 11:02 AM

I just started getting all the pieces of my 964 motor together and just discovered something and I need an experts opinion.

Piston #1 seems to have some corrosive damage. Possible causes are: leaving it in Berryman's Chem dip too long, or from previous owners abuse or previous rebuild. Regardless the pin easily slides through this piston where the same pin on the other pistons which show no damage, need to be pushed with a little force. I can also feel more side movement in the pin with the #1 piston. #1 rod bushing looks clean with no wear. I haven't seen any specs or measurements listed for this area of the piston. Machine shop said everything looked good, but maybe they missed this? Or could it be OK to use as is?

Please advise...

afterburn 549 · 07-30-2011, 02:08 PM

See what others think here...good for a bump any way LOL
But - i would consider a bushing for it...if a piston is costly....There are lots of other bushing in a engine....so why not? LOL
i did not say that was the answer,,,I just would table the idea

BURN-BROS · 07-30-2011, 02:26 PM

It looks more like a stain in the pics. Can you feel the damage with your finger?

Have the bore measured my a local machine shop to verify the diameter and any deviation @ that stain. You can use another piston as a reference on size. have them measure a pin while your at it.

NoEardGoat · 07-30-2011, 02:51 PM

I worked at the spot with some red scotch brite pad before I took the above pictures and it smoothed it out a bit, but I can still definitely feel it with my finger. It feels like it is above the normal piston surface, but if this were the case it would be a tighter fit with the pin... I am afraid if I work at it too much, then there will be way too much clearance between the pin and the piston's orifice. It almost looks like a casting imperfection?

I put the tools down, and everything is on hold until I figure this one out....

cgarr · cgarr's Garage

Almost looks like damage from someone pounding out the pins at one point?

NoEardGoat · 05:32 PM

Quote:

Originally Posted by cgarr

Almost looks like damage from someone pounding out the pins at one point?

Possibly??? Not by my doing, but maybe done by previous work.

The center section feels raised, but the sides fells like it is into the pistons surface. You can feel it with your finger and when the pin is installed there is a little movement that I can feel that doesn't exist in the other pistons... I will take it by my local Porsche mechanic and see what he says. I have a feeling his answer is going to be: "I wouldn't reuse it."

From what I have shown you in the pictures and explained would you use it or replace it?

If replacing, I am sort of hesitant to try and get another used single or used used set as their condition could be the same or worse...
JE pistons and use my barrels? This really sucks....

Henry Schmidt · Henry Schmidt's Garage

Give me a call. I probably have a replacement for a reasonable price.

NoEardGoat · 07-30-2011, 06:04 PM

Quote:

Originally Posted by Henry Schmidt

Give me a call. I probably have a replacement for a reasonable price.

That would be great. I will give you a call Monday, or sooner if your working this weekend?

M64/01
Tolereance Group: 3 (99.991 - 100.001mm)

Weight Class: - - (644 - 652g)

(You probably know these off the top of your head, but I thought they might help)

Henry Schmidt · Henry Schmidt's Garage

Sorry but it will have to be on Tuesday. I'm playing with my airplane on Monday.