Difficulty Removing Wrist Pins

[p911sc]

I am doing an upper end rebuild on a 1983 911 SC due to broken head studs. Today I removed the heads and began working on the piston cylinders. They are alusil so I am attempting to remove the pistons and cylinders together. Started with cylinder 1. Circlip came off without too much difficulty but I couldn't budge the wrist pin. After much effort, I moved to cylinder #4 thinking it might be easier and I could put a success behind me. Similar situation, in that the circlip came off easily but the wrist pun would not come out. I was actually able to move the wrist pin about 2 mm and it sounds like it is hitting a stop. Pushed it back and pulled again with the same result. There is definite movement but a click as it hits something.

Question #1: Any tricks to removing the wrist pins?? Heat piston with torch? Cool wrist pin with can of compressed air?

Question #2: When I was trying to slip the cylinder out to expose the wrist pin, it slipped off the piston. This was the cylinder with 2 broken studs and there was less in the way of friction to help keep it together. I know this has been the subject of much discussion but.....do I reassemble with existing rings? Just re-ring the one cylinder?

Any help is appreciated.
Rick

[davidppp]

Hello, Rick.

On the 3L especially the pins are quite tight in the piston bores.

The psitons need to be very hot to make removal easy.

This can be hard to do ..but if you force them you will likely damage something, bend a rod etc..

It is just possible with the right tools to remove the rod nuts with the pistons still on, and pull the rod and piston..e..then you can work on the pins and pistons on the bench much more easily..

[kstylianos]

Heat the dome of the piston with a propane torch. It dosent take much heat for the piston to expand just a little to make pin removal easy.

[ChrisBennet]

Heat will work if the piston isn't in the cylinder or you can make a little tool. My buddy Moe helped me make this one:



-Chris

[p911sc]

Great suggestions. Thanks.

I was going to ask about heating the domes. I would assume, as Chris states, that the pistons have to be out of the cylinders at the time. I will try this on the one that I have exposed. I have alusils, so I will be trying to take pistons and cylinders off together. With the others, I will try something similar to what Chris used. I am assuming that the wrist pins can be pulled either way, towards either the front or rear of the engine, as long as the circlip is removed?

With the cylinder that I inadvertantly pulled off the cylinder, are there any opinions about reringing versus reusing existing rings??? I know the recommendation is to leave them together but, at least with the one cylinder, the water's under the bridge.
Rick

[rlane]

Just went thru this and Chris 's tool is really great.There is enough movement in the rod/cylinder attachment that not very much of the force of a blow gets to the vector you need to move the pin, ditto with reinstallation as I found out the hard way ! (see my new post on rod bushing woes)
I had the same issue with cylinder moving and exposing rings, a decent ring compresor , care and all should be well.

[p911sc]

Richard,
Thanks for the good info.. I am definitely going to build a pulled like Chris shows.

I read your other post and got to reading a few of Chris' about inserting pins. On one of these posts, there is a statement about the wrist pins have a direction to them.... Anyone with experience on this? Am I trying to force something that wants to go the opposite direction?

Also, a stupid question. I tried a puller on the one wrist pin. I wasn't banging it hard, mostly tapping...anyway, I have read posts about the piston rods being more delicate than they look and fear set in. would it be obvious if I bent a rod?
Rick

[Eagledriver]

I just tap them out with a PVC pipe and hammer. Heat will help but I've not found it needed. I always pull the pistons out of the cylinders to check the ring wear even when I reuse the rings. I keep them on the same piston and try to put the gaps where they were when I removed them. Never had a problem with rings on 4 engines so far (3 alusil and 1 Nickasil).

-Andy

[p911sc]

Thank you all. I ended up using Chris's tool along with heat and tapping.

Now it's on to the studs.
RIck

P.S. I ended up pulling the cylinders off and will clean and re-ring the pistons.

[porschedude996]

I am splitting the cases so my story is different. I tried to get the pins out and since I'm splitting, I just disconnected the con-rod from the crank.

[gled49]

The reason the pins are tight on disassembly, is the pins, hammer on the wire locks during operation and create a ridge. All pins are a push fit in new pistons. I will very lightly hone the pin bore to reduce the ridge and return to push fit.

[brighton911]

Just because the piston came out of the bore, there is no reason not to re-use the rings. Unless of course the ring end gap is excessive. BTW, rings rotate during normal engine operation.

[PeteKz]

^^Agree. As long as you put the same rings in the same pistons in the same cylinders, you haven't changed anything. I prefer to remove them and check the end gaps while I have it apart.

In my early years with VW's and American engines, I've even got them mixed up, and put them back in the wrong cylinders. That didn't make any difference in running or compression tests. However, I don't recommend that...

[boyt911sc]

Originally Posted by PeteKz

^^Agree. As long as you put the same rings in the same pistons in the same cylinders, you haven't changed anything. I prefer to remove them and check the end gaps while I have it apart.

In my early years with VW's and American engines, I've even got them mixed up, and put them back in the wrong cylinders. That didn't make any difference in running or compression tests. However, I don't recommend that...

Peter,

I first met the OP in 2006 and now a close friend of mine. He eventually pulled the pistons out and re-ringed his Alusil cylinders. His car has been running well since then after almost 17 years from rebuilt. My SC was re-ringed too more than 25 years ago with more than 15K tracked miles and been very reliable. The story about Alusil cylinders not to be re-ringed is a myth propagated by some one famous. And it was a no-no to even remove the piston from the cylinders. Things has changed a lot since then.

Tony