Fixing poor leakdown, Cyl 1 leaks at 50%, rest are cool. |
|
Porsche, and the Porsche crest are registered trademarks of Dr. Ing. h.c. F. Porsche AG.
This site is not affiliated with Porsche in any way. Its only purpose is to provide an online forum for car enthusiasts. All other trademarks are property of their respective owners. |
|
Fixing poor leakdown, Cyl 1 leaks at 50%, rest are cool. |
VaccaRabite |
Oct 24 2007, 07:00 AM
Post
#1
|
En Garde! Group: Admin Posts: 13,554 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 |
Jake Raby |
Nov 1 2007, 11:25 AM
Post
#2
|
Engine Surgeon Group: Members Posts: 9,398 Joined: 31-August 03 From: Lost Member No.: 1,095 Region Association: South East States |
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. |
Lo-Fi Version | Time is now: 27th September 2024 - 07:51 AM |
All rights reserved 914World.com © since 2002 |
914World.com is the fastest growing online 914 community! We have it all, classifieds, events, forums, vendors, parts, autocross, racing, technical articles, events calendar, newsletter, restoration, gallery, archives, history and more for your Porsche 914 ... |