Inserting pistons into cylinders
 

Wayne's book states that a light coat of oil should be on the cylinder walls when inserting the pistons into the cylinders.

What is a light coat and how does one attain it?

Does that mean wiping it in from your fingertips and then lightly wiping off with a rag?

Is there a documented order to put the cylnders on so that the wrist pin clips are accessible? (Or just common sense of inserting one side, then working your way back?)

Chris,

I am no expert, but:

I wiped fresh 20W50 on the clean cylinders and coated the piston rings with a light coat of fresh oil. I put the pistons into the cylinders on my bench and then placed them on their correct rods. I coated the pins with assembly lube and started nearest the bell and worked my way back. There is an extreme possibility that your piston will slip out of the cylinder while doing this!

I created a "slide hammer" with a long 3/8" all thread, a handle with a hole in the middle, and stepped up washers and a nut on each end of the all thread. I could use this assembly to pull out the pins if the rings slipped out of the cylinder. I wish I had done this to take the pistons out originally. Work slowly and do not get upset (one of my issues). It will all go back together. Remember, it is easy to break the rings as they are very brittle.

I used a squirt bottle to get the cylinder walls and piston skirts and rubbed around with my clean hands...never had a problem....

Quick tip:

install the pistons into the cylinders from the bottom,install just enough so that you can install the piston pins, then install the piston/cylinder assembly to the connecting rods.

A light coat of oil is just what would be wiped on with your fingers you dont want the oil running to the bottom of the cylinder. ( another words if you see drips its to much)

More tips:

Put one wristpin clip in the piston while it is still on the bench.

Stuff rags behind the piston when you're inserting the wristpin clips in case the clip goes airborne.

-Chris

Put one wristpin clip in the piston while it is still on the bench.

yes good catch........

install the assemblies from the flywheel end to the pulley end.

make sure the right piston recess is up...

Tim,

I've heard that installin them upside down is a common mistake. My port cut-outs are so different in size, I don't see how I could miss it, but thanks...

Good idea on direction, probably more room that way...

Is there any good tool to help insert the wristpin clip? Just needlenose pliers probably eh?

Im not sure if you have circlips or eclips or simple spring steel clips. Long nosed vise grips are helpfull.

Wear eye protection when trying to install the clips in awkward areas..

the spring type a dulled screwdriver may help. place one end of the clip into the piston, and persuade the rest of the clip home with the tip of the screwdriver..

Now what about piston ring gap stagger?

Obviously the gap in the oil ring should go on top... But should the other two gaps be staggered 180 from each other, or about 120?

Use a piston pin as a backstop for installing the first piston pin - otherwise it will be very difficult...

-Wayne

Also, in the caption for the photo - I show using a clean room wipe to liberally coat the inside piston walls. Then clean the excess oil off...

-Wayne

hallo
On the Pistons Top you should have a E or a arrow , they must point towards the inletside .
harald

Thanks harald... I'm using RSR Mahle pistons with the valve pockets. The big pocket goes up. :)

Wayne, the new mahle wristpins just slip in. I read an article about this change about 6 mos. ago, can't remember why they did it...

Chris....I was very pleased when I found that out with my new Mahle set. I always hate having to tap/hammer/force wrist pins into a piston.

In the past, I have heated the piston with a heat gun, and frozen the pin for a few hours. But as you said, the Mahles slip in with no tricks required.

I installed my pistons into the cyinder from the bottom and they went in real nice! I put them in dry and will wipe oil on the cylinder before attaching them to the rods. When we rebuild our race bikes we build the nikasil cylinders dry. but the gas has oil mixed in!

Chris,
If the con rod small ends were rebushed, the machine shop should have honed each small end ID to provide the correct oil clearance for its new piston pin. 911s use a full-floating setup (bearing area in piston and rod).

The piston and cylinder should have an adequate oil film to prevent scoring when the engine starts up. The volume of oil splashed onto the cylinders during engine operation will far exceed the amounts in the above discussion. I wouldn't worry about it. However, don't install dry. You're going to crank the engine and build oil pressure before you fire it up anyway, yes? Yes.

Talking about oil, are you using some sort of high pressure lube on the cam lobes?

Sherwood Lee
http://members.rennlist.org/911pcars

Sherwood. Moly lube on the cams probably...

Rub the cam lube out thin or it may effect your valve clearance. I was getting inconsistent values when I was setting the cam timing once and I traced it to the valve clearance getting bigger as the rocker smoothed out and thinned the layer of cam lube.:rolleyes:
Help me out here guys, am I the only one that makes these stupid mistakes?
-Chris

I just came across this "oldy-but-goody" thread. I was going to put my pistons on the rods, then add the cyls, but I'm changing my mind and putting the pistons into the cyls on the bench.

I have tried both methods, and now always put the pistons in the cylinders on the bench. It works better for me.

cheers