Fixing poor leakdown, Cyl 1 leaks at 50%, rest are cool. |
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Fixing poor leakdown, Cyl 1 leaks at 50%, rest are cool. |
VaccaRabite |
Oct 24 2007, 07:00 AM
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#1
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En Garde! Group: Admin Posts: 13,475 Joined: 15-December 03 From: Dallastown, PA Member No.: 1,435 Region Association: MidAtlantic Region |
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 |
Cap'n Krusty |
Oct 24 2007, 11:11 AM
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#2
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Cap'n Krusty Group: Members Posts: 10,794 Joined: 24-June 04 From: Santa Maria, CA Member No.: 2,246 Region Association: Central California |
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 |
Oct 24 2007, 11:24 AM
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#3
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Viermeister Group: Members Posts: 4,254 Joined: 7-August 03 From: Vienna, VA Member No.: 994 Region Association: MidAtlantic Region |
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..... |
Cap'n Krusty |
Oct 24 2007, 01:24 PM
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#4
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Cap'n Krusty Group: Members Posts: 10,794 Joined: 24-June 04 From: Santa Maria, CA Member No.: 2,246 Region Association: Central California |
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 |
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