Supporting Piston - Removal of Pins?
 

I have searched and not found much. How are people supporting their pistons during the driving out of the pins?

I have used heat, but they are still tight - propane torch. Perhaps I am not heating them long enough?

The other part of this is perhaps I am over thinking this. I do protect the pistons from the studs with rubber hose.

Input would be appreciated. Thanks.

Have to ask- are you sure the pin clips are out? If I have a tough one I'll hold the rod in a vice(wood contacts) and drive the pin with a perfectly sized dowel. They normally aren't too tight but you do have to take care not to ding surfaces while working.

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In situation, same approach with the dowel and a towel/moving blanket in case the piston tries to escape.

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Ok. Thanks

I will pad more with the towel. That is a little difficult when you heat the piston.

Just use a nut, bolt and a pipe or deep well socket to gently pull them out, pounding them out is nuts.

Choosing a tool.........
 

You could use a wooden or plastic dowel to push out the wrist pin. And in some cases you need to pull it out. So a PVC puller is what I used. Heat application makes the removal and installation much easier. Here are some of the pictures to give you an idea of my homemade tools.

http://forums.pelicanparts.com/uploa...1553967904.jpg

http://forums.pelicanparts.com/uploa...1553967904.jpg

I have use these tools in more a dozen engine rebuilds so far and a very valuable tool for me. I prefer to do a left to right sequence for removal and installation. I can not imagine myself without these gadgets.

Tony

Thanks for the pictures and suggestions.

What diameter is the plastic pipe?

How long are you heating the piston with propane?

OK - Wrist pin diameter is 22mm. As long as my plastic pipe will fit that it should work.

I'm missing something here. I've never had to use heat. The home made pullers are simple and very effective, but I don't think I have ever had to do that either. A little tapping with a plastic hammer against something suitable, like a socket on an extension.

You don't freeze the pin and heat the piston to insert the pin, so why would heat be needed for removal?

Dempsey doesn't mention heat in his book - he describes using a screw driver for the tapping. Anderson notes: "The original pistons had a light press fit for the pin, so pistons had to be heated slightly for installation. The modern versions of these pistons has a slight clearance so the pins may be pressed in with a finger."

I don't know about Bentley, but on some details Clymer had some klinkers. Their description on how to remove the pressure plate included screwing in some bolts to relieve pressure, but did not note that this was for the 911 transmission only (or maybe the 901), and had no place in dealing with the 915 PP, confusing a whole generation of us DIYers.

Porsche's workshop manual for our cars, at least through the end of the SCs, is two books for the earliest models, and four or more books of updates. Perhaps the manual for the 2.0 model mentions this slight heating, but the updates neglect to mention you don't need to do it from some model on?

So I would suggest you put the propane torch away.

A couple of observations.

What motor is this? Actually Porsche says to heat pistons to remove the pins on some of the older motors.

Are the rods still installed in the motor?

An issue I have run accross is there could be a burr in the piston from the circlip. I have used a cutting tool to scrape this down to make the pin easier to slide out. I have also use a specially shaped piece of wood between the piston and the studs to steady the piston. This is especially helpful when installing the circlips.

This is a 3.0L. Rods are still in.

I am surprised that more people have not talked much about this. How long does it say to heat them?

I am going to build a piston puller tomorrow.

Heating was recommended for the 2.0 motors. Not sure if it was necessary.

On the 3.0 motors the pins should not be a tight fit in the piston. Just make sure there is no burr from the circlip and the puller should do the job. It could be that there is a build up of varnish on the pin essentially gluing the pin into the piston.

Same set up I've got, I also have 12 PVC spacers for holding the cylinders. Never had to use heat myself, so try it without first.

I imagine it could be varnish holding the pins.

I bought the PVC tube, and was not sure what to do with the remaining tube - cylinder holders.

Thanks for the pictures.

If you are going to create a tool to get the wrist pins out of the pistons/rods, let me suggest using a piece of threaded rod with the correct sized socket tool that will fit the end diameter of the wrist pin, a washer and nut on the threaded rod behind that, and at the other end of the threaded rod something that will fit over the threaded rod and has mass, such as a piece of pipe, followed by a washer and a nut.

What you are making is a slide hammer. You can hold the piston in one hand and repeatedly slide the mass against the washer/nut on the other end with your other hand. Worked like a champ for me!

I've just pushed them out with my fingers. Maybe light taps with a small hammer or a ratchet holding the piston in my hands.

My guess was correct about this "heat the piston" business. Volumne 1 of the factory manual says use an electric heater (the picture shows something I don't recognize sort of clamped on the piston) to heat the piston to 80 degrees C, then push the pin out with a drift. To install, heat the piston in an oil bath to 80, or use the electric heater, and push the pin in. It says that if you can push the pin in cold you need larger OD pins (which it names). That was for the 2.0 engine. V1 has some info on the 2.2 engines also, but doesn't mention the pin.

Volume 3, which covers through the SCs (at least the one I bought) says nothing about how to remove or install the pins. But as Wayne notes, Porsche changed this from a light interference fit to one where you can push it in or out without needing much force. The rod is plenty stiff enough to withstand some tapping on a drift of some sort. To each his own, but I'd not consider the extra time needed to use a puller.

As to what amounts to a slide hammer, those are only useful where you can't get to the other side of something. Using that technique on the pin is going to impose the same forces as tapping on a drift, plus some extra set-up time.

But I hope all who read this discussion realize heat isn't needed unless working on a 2.0. And maybe by now a new set of Mahle 2.0s have the slightly looser pin bore by now also?

I was thinking that the rods are very strong, that said mine were in tight. I did use the PVC buller, it did work well - zero stress on the rods. Perhaps not worth it, but it was what I used.

Eighty degrees celsius would not even boil water.

James - when you have everything cleaned up, you can see what it takes to push the pins back in on your work bench.

Doubtless some piston holes, while within spec, are at the narrow end, and maybe some pins at the wide end?

I've used a propane torch for a couple of jobs on my SC. I can set it on the garage floor upright, playing on the aluminum banana arm to heat it up so I can get an old bearing out, and later a new one in. Lots of mass there. No real risk of overdoing the heat.

To unfreeze small screws down in the distributor so I could disassemble and repair it, I hit on using the propane torch. I over did it - all the plastic bits inside melted (not hard to replace, though), but luckily I noticed the aluminum starting to look, well, different. It was, it was just starting to melt - I had to do some filing and grinding to get the cap to fit right after I was done. It did break the screws loose, though, and the distributor works fine.

But controlling temperature to 80C with a propane torch? I suppose with gloves handling the heated cylinders wouldn't be bad. But the flame is well above 80C, there is oil all about, etc. And the shop manual doesn't give a Porsche tool part number for the electric piston heater they say to use. One of the limitations of the shop manuals is they were basically written for Porsche trained mechanics. Wayne's book, and Bruces, were written for the likes of us.

We've all learned something from this, at least I have.

Thanks Walt, and to all for responding. Hopefully the pistons will be much more resistant to the heat from the propane.

Now cleaning the piston tops and ring lands. May split the case today.