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

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.

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

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.

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.

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.

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

Zach

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.

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

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

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

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.....

^^^
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

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.

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

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

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)

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.

i am pretty sure a type4 don't need no stinking rings

but don't take my word for it - i could be wrong

free advice is free for a reason

i'd be sunk with out em'

Man..... The Capt. nailed it.

Clayton

In the Jake Assembly video he installs the piston down into the cylinders and comments that the Type 1 guys like to install the cylinders down onto the piston..

I don't think it really matters which way you install them as long as you are

careful with the rings. I have always installed the jug onto the piston. But in this

case, in his situation I would put the jug onto the piston and leave the wristpin

alone.

Done it both ways. You can slide the cylinder onto the piston attached to the rod if you have one of those steel strip ring compressors. I bent one up from a steel strip but you have to unwrap it from between the studs when you remove it.

I personaly like putting the piston into the cylinder with one circlip in place and pushing the con rod into the assembled piston and rod end.

Seems like the last one I did had NPR cylinders which had an inner bevel at the base of the cylinder so the cylinder could compress the ring as you slipped it onto the piston.

Ken

I've done it both ways. I find getting the wrist pin retaining clips in the most challenging part so I usually install the piston on the rod first so I have as much room as possible for the toughest procedure. Pistons with short pin heights are really tough to get on the rods if you load them first. Circlips (KB retainer) and wirelocks (JE retainer) are really tough without room. Stock not so bad.

Dave

So, here is what I ended up doing.

I took out the circlip on the outside end of the cylinder pin, leaving the one in place facing the #2 jug. I used a small flatheaded screwdriver to start pushing the pin out, and then a pair of 90degree angled needle nosed pliers to finish pushing the pin out (pushing out the pin towards the open side, obviously).

I pulled the piston off, aligned the rings properly, and put the piston in the jug, and then put the piston and jug back on the engine. Went back on fairly easy.

Then I realised I had forgotten to put the little spacer ring between the jug and the block, so I got to take the piston off again to put the spacer back on.

The piston ang jug are back in place, and I just need to fix the bad helicoil on the #2 spark plug before I replace the head. Trying to decide if I want to do the time cert myself, or farm it out to the bug shop down the street.

Zach

Typically any leak at the sealing surfaces will effect the future ability of those surfaces to seat in the future, sometimes lapping doesn't cure the issue..

This sounds like it may be one of the cases like we are seeing frequently these days that have a collapsed register, needing mill deck work to remedy the problem..

The GA cases are the absolute worst.

Collapsed register?
Sorry, I don't know what this is yet. (learning every day)

Zach

for the purposes of a quick (not necessarily accurate....oh, Cap'n..) reply, i think the register is the opening in the case what the cylinder fits into. i would have called it the "hole in the case". register sounds more....... official

yup

I think Jake has cases routinely decked now so every part of the cylinder register is equal distance from the case parting line. I think with kits the builder is responsible for this. This leaves no irregularities that affect the seating of the cylinders to the case. As important, all cylinders start the same distance from the centerline. If the cylinders are clean and the same height, the deck will be the same and if the sealing surface of the heads are equal, it should seal better. It removes a variable. Spending a week with Jake taught me it's all about reducing variables and getting things clean. The hobbist can control some of this but, not all. Jake's remove some of the variables especially regarding the combination of parts.

Dave

Today with most cases being over 30 years old we have noted that the cylinder seating areas of most all cases have shifted creating irregularities that position the cylinder unevenly. This makes for uneven deck heights and uneven cylinder head clamping loads that can make for head leaks.

Today we deck every single register on engines we build and have a variance of 1/2 of one thousandth for this critical aspect of the engine blueprint process. I have seen some cases that have a .020 difference in cylinder seating surfaces and to make it worse many of them are collapsed in the center of the registers. All it takes is .005 or less to cause a head/ cylinder leak...

FYI- GA code cases are THE WORST about this...

The 2008 engine kit program is being refined currently to include the necessary case machining to eliminate this problem for kit builders.

Jake the area that was leaking on Zach's engine was on the inside of the cylinder and was an area about 3/8" wide. seemed to me to be very little leakage but enough to cause a loss in compression ( and leakdown ) that is why I told him to lap it. Being that it lapped out fairly easily would you still suspect a deformed register?

Well, tonight I re-leak downed the cylinder and the lapping I did back in October had zero effect. No worse, but no better.

How do I fix it?

How do I test to figure out what the actual problem is?

Take the engine to your machinist and have them check the measurements. It will be cheaper and easier in the long run. The cylinders have to be checked and the head has to be checked so that it can all be made true.

OK, I had more than a second to think on this and here are some things you can do to help effect your repair:
- With each piston on that side at TDC measure the distance from the top of the piston to the top of the cylinder and compare.
- Do you have base gaskets on both cylinders? You can shim the cylinder that has the lower piston to cylinder top clearance.
- If you check the cylinder top to piston clearance and everything is cricket then you need to have your head worked on. It can be fly cut to bring the levels within spec. I dont remember, did you check the cylinder to make sure it was cool? I ask because, well, you know Do these simple tasks and get back with the measurements.

No gaskets at the base of either of the cylinders. I'll be pulling the head maybe tomorrow.

How can I get an accraute measurement without the cylinder moving with the head off?

Zach

They make special tools for this....but you can just put a deep socket on two of the corners of the cylinder, catty corner to one another and hold them down with the nuts. You get the idea, I am sure you can make it work. No base gaskets, eh? Hmmm. This may be a good sign as it gives you some wiggle room to move the shorter cylinder up to the hight of the taller one.

Drop a straight edge across the cylinder tops too. Careful when tightening the socket on the head stud, you can crack a fin if you torque it down too much. I've used this method before but I question how accurate it is considering you cannot get the cylinders properly torqued to the case this way.

If a register is collapsed and a cylinder is sitting on an angle the case will have to be decked. You should be able to see this with a straight edge at the cylinder tops.

I would measure the cylinder length with the cylinders off the engine with a set of calipers. If you compare side to side from the piston tops, you can be introducing error from different con rod lengths, piston pin heights, and differences in cyl to case torque. With the cylinders off you can also drop a straight edge across the cylinder registers check the registers again.

-Chris

Well I had time to work tonight, so I did more testing - just to make sure. I also did some experimenting with the leakdown tester.

1) the directions say not to run the leak down tester above 80 psi - but they don't say that you get a false reading if you run it below 80 psi. I was running it tonight at 70 PSI to be nice to the tool, and could not figure out why all my measurements were 10% higher. But it back at 80PSI and it was golden.

2) The leak down tester was leaking in 2 places. I put in some fresh teflon tape and that was fixed. I was REALLY hoping that was the cause of my leakdown - jsut the tool being out of whack. But, it wasn't.

I checked the valves for bubbles, and they were sealed tight.

The cylinder to head join only bubbled in 1 location - between the cylinders. Everywhere else seemed to be fine.

Tomorrow morning I am going to pull the head and start taking measurements. I really hope I just need to get the head recut a little.

Zach

Use an open flame around the sealing surface to check for leaks... When the flame flickers you have a leak....

You said this was a second hand kit of mine, who did you buy iit from and what serial number was the kit???

I got the engine from Evan Thompson. I havn't got a clue what the SN is.

Zach

I pulled the heads, and then made some spacers out of some 1 inch square tube steel stock i had laying around, and used them to re-tighten the cylinders down. I did not tighten them to spec, as I was concerned about breaking a cooling fin, but I got them to where the cylinders could not move.

I put a level with a good straight edge across the cylinder bank and looked for gap. If the level was square on the #2 cylinder, then there was a bit of gap on the #1 cylinder. This was somewhat expected, all things considering.

Using feeler gauges, I measured the gap. Where the bubbles were forming (#1 cylinder, facing the #2 cylinder) there was a .007 inch gap. On the opposite edge (facing the flywheel) was a .005 inch gap. In my leakdown-bubble tests, in the spot with the .005 gap showed no leak (no bubbles).

I don't think I can manipulate my calipers accurately enough to measure the lip of the inside of the #1 cylinder.

It seems pretty clear to me that the cylinder is either sitting slightly cocked, or is not squared off at the top. I'll have to measure that tomorrow.

Zach

Okay, so I measured deck height today with Josh's help.

#1 was the same as #2. I don't have to get my case decked!

Its a problem with how the heads were cut. The heads need to be recut, taking as little material off as possible. I took off the tin and all the other bits today, the heads will come off tomorrow after I do some baby shopping with the missus.

Zach

how many cc's are they now? are you running carbs or f.i.?

mike

Just dont forget to swap the heads and check to see if the difference is in the fact that the heads was swapped ?? as there was a CHT hole where there shouldnt have been one. It'll take 10 min to do as an xtra precaution and settle the matter once and for all.

Josh

OK, with the risk of being chastised by the Cap'n, I'll stick in my $.02:
How did you come to the conclusion that the head needs machining? You found the problem: the top surfaces of the two cylinders are not even. You found gaps of .007 and .005. Now you have to find out what is causing that variation. Just because the deck hts are the same, doesn't mean the problem is in the head. The top surfaces of the cylinders must be even. I would check both cylinder lengths and check the top ends for flatness. You may need to have the case decked. How did you measure the deck hts? If you want things to be right, you've got to measure everything until you find the source of the problem. The person that assembled the engine may have shortened one cylinder because the deck hts weren't even, not thinking about the heads sealing. You're on the right track, just keep measuring..

Just trying to help.

I agree that you need to have the cylinder lengths checked. It sounds like the one may have an uneven head surface. If this is the case you can have that fixed and then place a gasket under the cylinder to even up the heights. You should also have the head surface check, of course. It sounds like this is what you are going to be doing. IIRC, you checked the registers using a straight edge and going at it from various angles.

Bzzt. I'm wrong again.

Now I think that the heads are fine...

I swapped the heads (put 3&4 bank on the 1&2 side, and vice versa) and re-did the leak down. So the #1 cylinder head was now on the #4 cylinder, and the #4 cylinder head was now on the #1 cylinder.

I re-did leak down on Cylinder 1&2&4. I skipped doing leakdown on three.

Cylinder 1 (Head 4) still leaked at 55%.
Cylinder 2 (head 3) was cool at 7%
Cylinder 4 (head 1 - which I thought was the leaky one) was also cool at 7%

I measured the #1 cylinder from behind the shim to the mating lip, but was not able to get a measurement I was able to replicate from time to time.

But I now either need to go back to either that the cylinder needs shimmed up about .005 inches, or the case needs decked.
*edit* actually, I need to get the cylinder measured by someone who can replicate the measurement. Mine seemed to vary too much for me to put any stock in it. */edit*

I had negated my previous theory as Josh had suggested that they way I went about it was inaccurate. But, I am going to try my spacer before I deck the case. Now I just need to find a .005 inch cylinder spacer.

I also talked to Evan yesterday, and checked out a lead he had remembered, but it, much like communism, was a red herring. Would have been sweet if it worked though.

Zach

You cannot shim just one cylinder! Both cylinders must have the same deck surface.

Pull the cylinders and put a piece of 1,000 grit sand paper on a perfectly flat piece of glass.. Use some Dykem machinist dye on top of the cylinder to use as a control..

Make a pass over the 1,000 grit and see if any portion of the seating surface appears to be even or erratic.. You may have a warped cylinder seating surface..

My bet is still a drooped case register...