Fixing poor leakdown, Cyl 1 leaks at 50%, rest are cool. Options

[VaccaRabite]

So, at the Sterling meet I did a leakdown test on my motor, and found a problem with Cylinder 1. 45% leakdown, but 120 lbs of compression. Was tempted just to let sleeping dogs lie, but pulled the head off.

What was going on was clear as soon as we did that, the head was not totaly sealed to the cylinder, off by a very small amount. Instead of having the head recut, I decided to try and lap the two of them together.

So, last night I hand lapped them, using ground graphite to check for even contact. I got good contact after the third round of hand lapping (lap, clean, check).

Now I need to get the jug back on the block. I have a ring compressor on the piston, but I can't ficgure out how to get the head back on. Do I have to take the piston head off the rod?

If so, how do I get it off. It looks like that tis a spring keeper that needs to be removed. Is there anyhting on the rod the needs to be loosened before I can pull the pin out to remove the piston head?

Obviously, if there is a trick to getting the jug back on without pulling off the piston head, I'd like to do that.

Zach

[Brando]

DO NOT take off the piston. If you do that then install the head, how will you get it in the cylinder?

After you get the cylinder seated down all the way to the block, simply line up the head, studs going through the holes. You may have to move the studs a bit (they will give a little bit) to align them with the holes. It should drop right on then.

[VaccaRabite]

Maybe I was not clear.

How do I get the cylinder on? The head is easy. I understand that part.

If I take off the ring compresor, the piston rings expand and the cylinder won't go over the piston. It stops at the rings.

Zach

[type47]

it may be difficult to install the jugs on to an engine with the pistons connected to the rods. if one was rebuilding an engine, then the pistons can be installed into the cylinders on the bench, then push the piston toward the bottom of the cylinder to expose the piston pin holes but not so far as to free the rings, then, with the crank turned to expose as much of the rod as possible, mount the piston on the rod and insert the wrist pin. you have your piston already on the rod on the "short-long" block. you can try to use the ring compressor to compress the rings (guess that sounds kinda "duh") and put the cylinder on the piston and attempt/try to basically "push" the ring compressor "off" the rings by pushing the cylinder onto the piston. you are probably doing this exact thing but it's hard to do it this way as you are experiencing. if this doesn't work, you can remove the piston from the rod (easily done to tap out the wrist pin) and assemble on the bench (as mentioned before) then mount on the rod. there is one or 2 problems encountered (or at least, that i encountered): one is having the clearance to get the wrist pin "out the other side of the piston" before it hits the next cylinder and two is depending on the cylinder, the oil filter tower gets in the way of installing the p/c next to it and can only be accessed from the side opposite side of the p/c. i don't think you'll have that problem as that is #4 p/c (i think) next to the oil filter tower and i seem to recall you were removing #2 (?) cylinder.

[blitZ]

You need to take the piston off the rod. Remove the retaining clip on the side of the piston facing outward from the case. Remove the wrist pin. The piston should be pushed in from the top of the cylinder. Once in, slide it down so the holes for the wrist pin show and the rings are still in the cylinder. Then you can attach the piston back to the rod. Check your pistons as they may need to go in a particular direction, should be an arrow.

[geniusanthony]

Lemme try and work this out in my head. Cylinder 1 p/c, If you remove the circlip from between the cylinders with a pair of 90 degree cirlip pliers

Note on pliers: get a pair in which the jaws close all the way not just almost, I got a pair from home depot with interchangable pins I think Vise grip brand perhaps, point is they had enough slop in the end that in trying to remove the circlip, they would not fully compress the clip to remove it from the groove in the piston.

Moving on, pull the inside circlip, drive the wristpin from the oil cooler side with a drift that fits inside of the circlip on the driven side...a deep 10mm socket sounds about right for diameter. once that wristpin is out, pull the piston off. Mark which way is up on the piston with a marker or paint pen. Remove the remaining circlip, put it back in the other side (the inside of the cylinders side) and you are ready to compress the rings (offset the gaps 120 degrees first) and noting that the upmarking on the piston is pointing the same way as when remove. Drive the piston into the cylinder slowly, if you meet stiff resistance STOP and make sure that a ring hasn't come unseated.

Any spacers that were under the cylinder should be back in place now, and with rod 1 at TDC or close, and the piston in the bore at the bottom so that the wristpin hole is fully exposed. Put the pin into the piston a bit then slide the rod in place and finish inserting the pin and reinstalling the circlip. Seat the jug and you are done.

Experts feel free to chime in as its been awhile.

[VaccaRabite]

Okay, I thought that was what I'd have to do. Getting room to tap out the pin is going to be interesting.

Zach

[type47]

i reread your first post and i'm sure you know that to put the cylinder on the piston or the piston on the cylinder, (if you have the p/c on the bench) you compress the rings with the ring compressor (duh again) and hold them compressed with one hand, put the piston on top of the cylinder with your second hand and with your third hand, gently tap the piston into the top of the cylinder, the ring compressor will keep the rings flush with the sides of the piston allowing them to not prevent the piston from sliding into the cylinder. if a ring slips out of the compressor and expands, you start over. i had to start over several times when i did it.

[geniusanthony]

Talk about some fast replies eh??
The best non-club club ever

[Dave_Darling]

We put the cylinders onto the pistons, not the pistons in the cylinders, right? Don't you compress the rings, slide the cylinder as far onto the piston as we can, then tap the cylinder so it slides the ring compressor down while going over the piston?

--DD

[Cap'n Krusty]

Well, isn't this confusing? First the question, then the mostly CLUELESS answers. As I understand the question, you removed one cylinder and effectively cut it to seat in the head. How did you assure it was perpendicular to the head when you did that? How do you know the cylinder height is EXACTLY the same as the one next to it? How do you know the top and bottom seating surfaces are EXACTLY parallel? How do you know the head has BOTH cylinder mating surfaces EXACTLY parallel and the same depth? What were you thinking? They don't exactly make those things out back of the house with a hacksaw and a file, even in China .................

As for installing the cylinder over the piston, the CORRECT procedure at this point is to compress the rings with a ring compressor (after making sure the rings are properly aligned) and slip the cylinder down over the piston, making sure you con't catch any rings in the process. Then install the head. however, I think you've just wasted a WHOLE BUNCH OF TIME, not to mention introducing a bunch of variables that weren't there before. Of course that's just my opinion, I could be wrong, even after 37 years of Porsche engine building.

The Cap'n

[type47]

As for installing the cylinder over the piston, the CORRECT procedure at this point is to compress the rings with a ring compressor (after making sure the rings are properly aligned) and slip the cylinder down over the piston, making sure you con't catch any rings in the process. Then install the head. however,The Cap'n

(IMG:style_emoticons/default/biggrin.gif) wouldn't you attach the piston to the connecting rod via the wrist pin before you install the head?

geez Cap'n, i always read your very informative responses but your tone, even on an internet is read as very condescending. i'm here to learn and might appreciate a little more of a lighter attitude. not a sermon, just a thought.....

[VaccaRabite]

^^^
If I have to have the head recut, then I do.

My goal here was to try and mate the cylinder to the head better, as it was off by a very small amount. I did this by getting some lapping compound, and lapping the cylinder to the head by hand. When I get it back together I'll redo compression and leakdown. It might fix it, it might have made it worse. If it made it worse, the head will need to go to the machine shop any way. I won't figure that out until I get it back together. Either way, I removed a very, very small amount of metal through lapping.

All told, if I wasted time, then I suppose I'll never get these 2 hours back. Given the amount of time that I have spent working on this car in general, I'm cool with that. I'd rather be able to do it myself anyway.

Zach

[brer]

I used to love the book "how to keep your aircooled VW alive"

step 1: pull your hair back and put it in a ponytail.

(IMG:style_emoticons/default/biggrin.gif)

[Cap'n Krusty]

As for installing the cylinder over the piston, the CORRECT procedure at this point is to compress the rings with a ring compressor (after making sure the rings are properly aligned) and slip the cylinder down over the piston, making sure you con't catch any rings in the process. Then install the head. however,The Cap'n

(IMG:style_emoticons/default/biggrin.gif) wouldn't you attach the piston to the connecting rod via the wrist pin before you install the head?

geez Cap'n, i always read your very informative responses but your tone, even on an internet is read as very condescending. i'm here to learn and might appreciate a little more of a lighter attitude. not a sermon, just a thought.....

Condescending? I meant it to sound exasperated. We DO NOT NEED flat out wrong answers getting into the archives, and we DO NOT NEED people doing procedures without thinking them out, and maybe getting GOOD answers BEFORE they do things that can further exacerbate the problem. I am pretty careful NOT to answer questions I'm not familiar with, and when I make an error in my answer, I IMMEDIATELY retract or correct that answer upon being reliably informed I'm in error.

As for the reply from the original poster that he's ready to have it head cut, if need be, he's ALREADY likely caused further damage by grinding on the cylinder, something that cutting the head isn't going to fix. I call things like this a "can'o worms", don't you? That "small amount" is rather nebulous, as .001" can be a "small amount", as can .010". How do we know? Both introduce randomness to an otherwise precise equation.

I wouldn't remove/have removed the piston in the first place. One, you can easily damage the circlip, two, you can easily lose the circlip, and Murphy says it'll fly into the opening where the cylinder mounts into the case.


The Cap'n

[Elliot Cannon]

It is sometimes hard to tell if someone is condescending, angry, scolding etc. on a forum like this. You read the written words of someone and interpret them as you like or as you perceive them to be. Try not to be so sensitive. We're lucky to have someone like Capn Krusty offer his advise and wisdom of 37 years in the business. Take his advise and ignore what you might perceive as condescention etc. I know mechanics who REFUSE to offer free advice because they don't think people should work on their own cars. Their knowledge is in many cases their only marketable asset. Many don't give it for free. Thanks Capn. Keep the info coming. I apreciate it much. Seems I learn something every time you post.
Cheers, Elliot

As for installing the cylinder over the piston, the CORRECT procedure at this point is to compress the rings with a ring compressor (after making sure the rings are properly aligned) and slip the cylinder down over the piston, making sure you con't catch any rings in the process. Then install the head. however,The Cap'n

(IMG:style_emoticons/default/biggrin.gif) wouldn't you attach the piston to the connecting rod via the wrist pin before you install the head?

geez Cap'n, i always read your very informative responses but your tone, even on an internet is read as very condescending. i'm here to learn and might appreciate a little more of a lighter attitude. not a sermon, just a thought.....

[scotty b]

Cap'n he has done no damage. The blowby was VERY minimal all he did was use some valve grinding compund between the cylinder and it's mating surface in the head. I told him to use a sharpie marker to give it some color and only lap until all of the marker was gone. I'm not you but I have done this procedure MANY times myself with no ill effects.

Assumptions are the mother of all Fuchups right???

Zach the cylinder CAN be put back on like you have it with some care. First you need a flywheel lock to keep the engine from moving. Make certain your rings are sitting correctly (notches NOT lined up, preferably equally seperated) put the compressor on the rings, slip the cylinder onto the very end of the cylinder and gently tap it over each ring. Waxth CAREFULLY to make sure the ring is fully compressed and that it doesn't get cocked or slip out. A second set of hands is almost a necessity to keep the studs lined up with the holes in the cylinder. Make sure the flat part of the cylinder is on the INSIDE ( center of the case)

[KELTY360]

geez Cap'n, i always read your very informative responses but your tone, even on an internet is read as very condescending. i'm here to learn and might appreciate a little more of a lighter attitude. not a sermon, just a thought.....

With a name like Cap'n Krusty what did you expect....sweet nothings whispered in the ear?

I really appreciate the Cap'ns straight forward style. The best mechanics I've ever found were a little crusty, but honest and fair. Besides, ya gotta love a guy who uses 'exacerbate' in a sentence.

[jimkelly]

i am pretty sure a type4 don't need no stinking rings (IMG:style_emoticons/default/smoke.gif)

but don't take my word for it - i could be wrong (IMG:style_emoticons/default/icon8.gif)

free advice is free for a reason (IMG:style_emoticons/default/wub.gif)

[orange914]

Talk about some fast replies eh??
The best non-club club ever

(IMG:style_emoticons/default/thumb3d.gif)

i'd be sunk with out em'