Balancing pistons
 

I've been told that if the pistons are out of balance you would typically remove material from the wrist pin to balance it out.

What if the pistons are up to 11 grams out of balance and enough weight cannot be taken out of the wrist pin?

Can weight be taken out of the piston itself or is that unheard of?

Just curious since my local machine shop has told me its OK to remove the weight from the pistons without concern.

Thanks
Brian

I have swapped pins between pistons to get the spread in weights reduced, but never removed material from them. The pins are just too hard to remove material. I always remove material from the piston, usually from the side skirt.

I'm surprised you can't get them balanced by putting the heaviest pin into the lightest piston, etc, etc. I'm gotten a "perfect balance" that way and never had to remove more than a few tenths of a gram at worst.

zbph10

Why do I get a buzzing in my head telling me that you might have pistons from different weight sets.......hmmm

Did you replace some pistons?

Previous owner gave me a receipt from a rebuild done about 15,000 miles ago which included replacing P&C.

He told me the shop put in "new" P&C but I have to question that considering what I'm seeing. The heads weren't done, they left in the dilavar heads studs (4 broken and the reason for second rebuild), oil leaks, and it doesn't appear any of the bearings or rod bolts were touched. Half arsed attempt at best.

I had the heads rebuilt by Henry and bought Wayne's superkit with the ARP rods bolts, new steel head studs, new bearings, seals, rings, gaskets, sensors, etc. basically just about everything is being replaced or rebuild so I know what I have.

I agree they must have mixed and matched a few sets to get six good ones instead of putting in the "new" ones as told but that's just a guess.

My question is, how much weigth can I take out of the pistons without compromising them? I really don't want to spend any more money on this rebuild but maybe I could find a decent reasonable priced set of euro's to stick in if these are a no go.

Thoughts?

Name of the shop on the invoice??

Cheers

Al Morales is exactly right.
The pistons are classed with a maximum of 8 grams apart.
And in actual use more like 2 or 3 grams. And then matching piston pairs to less than 1/2 gram.
Some one that didn't know used a piston and cylinder from a different class. Obviously not a Porsche tech, who would have learned this the first week on the job.

zbph10

I would first identify the pistons and see if they are of the same weight class.......one can tell by the last digit of the part # they will all be the same....there is information floating around that will help you with this identification.

I have taken weight of pistons many times but from other applications, not Porsche. We are talking here about a fair amount of weight.....the only way I would do it is if I had a core piston for me to cut down the middle nd see where the meat of the piston is.

Basically Porsche engines are bullet proof if built right, with great attention to detail. Yes, Porsche has a lot of diferent components and in part it was done to eliminate rif raf from working on their engines.

A "mechanic" or "shop" without intimate knowledge of a Porsche engine is like playing Russian roulette with three bullets instead of one.......someone is going to get hurt....for sure.

That is one of the reasons why you see the purists do endless research and decide to tackle the job on their own.....they have figured that:

1) I don't know what I'm getting for my hard earned cash and most of these "mechanics" are of the midnight variety where once the bill is satisfied that is when the warranty and most importantly the job ethic ends. So you are out the engine and the cost.

2) What can bring you more pleasure than working on your own baby....yep, you can defenitely mess up, but from the moment you arrive at the decision you probably know more about the engine than any of the "mechanics" and "shops" I'm talking about.

3) Last but not least we are fortunate to have a vast following of the brand and you can always find someone with the answer, sometimes they will take time from their schedule to come to you and help with your problem.

Now isn't life beatiful?

Good luck and keep us posted, your experience becomes part of our experience.

Here's a copy of the receipt from
EUROPEAN AMERICAN AUTO SERVICES in Algonquin, Illinois for the piston and cylinders that were replaced 20,000 miles ago by the previous owner. I've put on about 5000 of those miles.

http://forums.pelicanparts.com/uploa...1169099957.jpg

I'm so disappointed, I was positive MM was going to make an appearance...

Who's MM?

Call te shop up and find out if they remember what they installed and where they obtained it? That might shed some light....

Re: Balancing pistons
 

If you want a perfect match and can't get it with the wrist pins, it is just fine to take it out of the fat part of the piston skirt. This is a very low load-bearing area and it usually only takes a very small amount of material to get a perfect balance.

If you have to balance the pistons, you can take some material off from under the dome, keep it central and sont go too crazy, obviously measure the thickness of the dome to be sure your not going to go too thin. Stay away from the wrist pins as an alternative.....theyre as hard as wedding dick