1970 911s Engine Rebuild - Frozen Pistons

[GenX Porsche]

I have undertaken a learning project of rebuilding a 1970 911 S Engine. To everyone's suprise and mine I have actually gotten to taking off the piston cylinders. Now the issue came up that my pistons were frozen. The frustrating parts that that I can get piston number 4 off but number 5 and 6 are still stuck. I haven't attempted numbers 1 - 3 only to assume the worse. I have tried alot and now I turn to the masses for wisdom in the subject. I could use any and all help. I have heard the problem being solved with cutting off the cylinder from the piston but the problem is this is a low budjet project. Please help me......

[Jim Sims]

Elaborate on your problem: Did the engine turn over (rotate freely) before you began the disassembly? Is it the cylinder (finned barrel) that is stuck? Does it move some and then hang up on the piston? What do you mean by frozen pistons? Stuck or jammed rings? Jim

[BK911]

Not sure of your exact problem, but I doubt this will be a budget rebuild. Especially if you need new 2.2S P/C's. If your problem is frozen rings holding the piston in the cylinder you might be able to get some penetrating oil to work. Rotate the engine on the stand so 1-3 are up and load up on the oil. Wait. Wait some more. Wait a little longer. Then attempt the removal. When/if this works repeat the process on 4-6.

Good luck!
BK

[GenX Porsche]

To elaborate on my problem. I cannot remove the cylinders. What happens is that I can wiggle the cylinder back and forth but only a very small distance. To put it another way I can feel the distance when I rock the cylinder back and forth but I cannot measure it with a feeler gauge or visually see the difference. The way I got one cylinder off is by sitting there for 30 min just rocking the cylinder back and forth to the point where i finally got it off. I suspect that the issue lies in the piston rings. The engine has been outside a car for over 3 years, could be more. The engine didnt turn over as long as I have had it.

[Jim Sims]

The cylinders may have a wear ridge on them above and below the section where the rings normally run. The rings have worn this section more than the rest of the cylinder surface and you can't get the rings past the end of these wear sections. If you could get to the connecting rod bolts on the stuck piston (this means the cylinders have to come off the other side of the engine though and you may have the same problem there) you could use a ridge reamer on the head end of the cylinder and then push the pistons out through the head end. You could try heating the cylinders and more force and wiggling; I suspect if there is indeed that much wear the cylinders must be replaced or renewed. Or as last resort cutting them off. Also, IMO, in the context of rebuilding other types of engines there is no such thing as a "budget" 911 engine rebuild. Jim

[john walker's workshop]

if they're that frozen, there's probably a lot of pitting in the cylinder, and you won't be able to use it anyway. go easy and don't screw up the piston. if you can save the pistons, you can find some 2.2 or 2.4 cylinders easier than S pistons. soak with penetrating oil, not WD40, and use the wooden or rubber handle of your hammer to lightly tap the piston. the rod bolts face the piston by the way.

[Jim Sims]

You're right, John. The rod nuts would have be cut off with something like a flexible head dremel tool. There's probably not room and there's the likelihood of cutting the rods. I wonder if a special tool could be made to reach around the rod big end to get to the rod bolt heads - probably not, but I'm going to look at an old case tonight. Jim

[GenX Porsche]

From the one piston that I took off there seems to be no scoring of the pistons at all but that is just piston number 4. The engine was introduced to the elements when it was out of the car so someone once told me that the rings were rusted to the cylinders. That would be very bad. Also the thought crossed my mind that if I could get three pistons off one side that I could crack the case and then detach the stuck side from the crankshaft and then I could tap each piston with a piece of wood and a mallet. Currently one of the cylinders is being soaked but it hasnt loosened it up yet.

[john walker's workshop]

you can tap them with a piece of wood just as they are. all the way up or down, where the rod would be on the same plane as the piston would be the least yielding position. anywhere else you may get it to move.

[cstreit]

Liberal use of a good penetrating oil overnight is certainly worth the try though... At least you might save the pistons!

[Jim Sims]

Looked at an old case and a spare rod and John Walker is definitely right; there's not a prayer of getting to the rod bolt heads or nuts with the cylinder barrel in place. There's the slots through the main bearing webs but the crank will still be in the way. Barrels have to be forced outward towards heads!

[Early_S_Man]

I think a couple of days soaking both banks with the cylinders up and liberal amount of penetrating oil covering the outer periphery of the piston tops is called for before trying to loosen up anything. At the time you decide to proceed, sequencing which piston you decide to pick first to bang on is important ... it needs to be a piston that is mid-stroke in the cylinder, an NOT at TDC ot BDC!

I believe a 5"-6" section of 2" x 2" lumber placed squarely in the center of the piston top, and hit squarely with a plastic mallet or dead-blow hammer will not present much danger to the pistons. I believe the hits should be made on all of the cylinders that are mid-stroke ... in sequence, not repeatedly on just one cylinder!

I reiterate ... DON't BANG ON ANY PISTONS AT TDC or BDC!!! Good luck!

[GenX Porsche]

Thanks everyone for their input. It has helped alot. Look at this post in about a week and if you guys are interested in knowing the results. I just have one last request and that is if anyone could suggest the best penetrating oil for this kind of job. If this engine ever breaths life it will be thanks to all of you.

[kpmurray]

One of my toolmaker friends recommended Kano Industries Sili-Kroil to me for freeing rusted together items.

His company used it to separate matched dies that were of close tolerance, but that had rusted together. He had a hobby of restoring old farm equipment that had been outside for years and had sucess. I've also used it on several old cars, an airplane and in general shop.

The stuff contains a small amount of silicone oil along with the hydrocarbon "vanishing oil." As a chemist, I can vouch that the silicone lowers the surface tension of the oil, and allows for better penetration. Also, when the hydrocarbon part evaporates over time, the silicone remains and minimizes corrosion.

Be careful using it on parts that you intend to paint, unless you use a conditioning cleaner to remove the oil. Finally, be patient and wait for the stuff to work- it costs you less money in the long run.

[Superman]

Maltby's Penetrating Oil. Available where diesel mechanics shop.

[hdoody]

If the various penetrateing oils do not work(wich they may not), use brake fluid. You must clean the residue off as soon as you have the jugs off.(very corrosive) This WILL Work!!!!!!! Brake fluid will disolve carbon off of pistons and or combustion chambers very well. Makes them look new.

[john walker's workshop]

maltby is my favorite. got em off yet? if you do use heat, don't forget that stuff is flammable.

[GenX Porsche]

I just picked up some of the Kano stuff so I am giving it about a day to let it all soak in and then I am going to take my rubber mallet and piece of wood and see what can happen. Thanks for the tip on the brake fluid I would never had guessed that at all. If this doesnt work I am going to try the brake fluid.
David

[Jim Sims]

Did you ever get those barrels off? Jim

[GenX Porsche]

I got cylinder number 2 off. So that leaves me with 1,3 and 5,6 still on the engine. My main problem right now is that pistons 6 and 3 are at TDC but 1 and 5 are in mid-stroke. I have soaked all of them in the Kano stuff and little improvement is there but I still cant get any real signs of the others coming off. I still need help any suggestions would be wonderful. I am currently soaking 1 and 3 right now.
David