2.0 Cylinder Gaskets, Should they be used? |
|
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. |
|
2.0 Cylinder Gaskets, Should they be used? |
jack20 |
Apr 9 2020, 12:43 PM
Post
#1
|
Member Group: Members Posts: 412 Joined: 7-November 14 From: Granite Bay, CA Member No.: 18,099 Region Association: Northern California |
Hello,
I had leaking pushrod tube seals and dropped the engine to make the job easier. I decided to pull the heads to check condition. I’ve done quite a bit of reading about whether or not gaskets should be used between the cylinder and case and between the cylinder and head. Some posters point to a service bulletin stating not to use gaskets. I have metal spacers/gaskets between the heads and cylinders. I think this engine has been rebuilt once before I got it. It runs well but it’s not as quick as another 914 2.0 I had years ago. Maybe the other car had higher compression and no gasket? I’m wondering if this metal gasket should be there. I haven’t checked for a gasket between the cylinder and case. My 356 has a thin copper gasket between the cylinder and case. Can anyone shed some light in this? Thanks in advance, Jack |
Superhawk996 |
Apr 10 2020, 06:55 AM
Post
#2
|
914 Guru Group: Members Posts: 6,469 Joined: 25-August 18 From: Woods of N. Idaho Member No.: 22,428 Region Association: Galt's Gulch |
I understand that the laminated metal gasket can be problematic but what is so unique about VW Type 4 heads that makes them fail? Laminated metal gasket is commonly used on water cooled engines all the time.
Maybe the fact that heads run so much hotter than a water pumper? Then I wonder, why not use a different material like copper? Norton Commando's use a copper head gasket and they are air cooled. I think some other Brit bikes used copper as well. I suspect that in the end the aluminum head is soft enough vs. the steel jug to deform and basically form it's own seal and account for a 0.0005" - 0.001" inconsistency between any of the mating surfaces. Sort of odd that air cooled 911 heads use a head seal though? Like other's I haven't used laminated gaskets but as I read this thread I'm wondering what the real development history behind it was. |
HAM Inc |
Apr 10 2020, 03:53 PM
Post
#3
|
Senior Member Group: Members Posts: 846 Joined: 24-July 06 From: Watkinsville,GA Member No.: 6,499 Region Association: None |
I understand that the laminated metal gasket can be problematic but what is so unique about VW Type 4 heads that makes them fail? Laminated metal gasket is commonly used on water cooled engines all the time. Maybe the fact that heads run so much hotter than a water pumper? Then I wonder, why not use a different material like copper? Norton Commando's use a copper head gasket and they are air cooled. I think some other Brit bikes used copper as well. I suspect that in the end the aluminum head is soft enough vs. the steel jug to deform and basically form it's own seal and account for a 0.0005" - 0.001" inconsistency between any of the mating surfaces. Sort of odd that air cooled 911 heads use a head seal though? Like other's I haven't used laminated gaskets but as I read this thread I'm wondering what the real development history behind it was. Excellent question, and the answer hits at the heart of the problem. For the laminated gaskets to stay laminated they have to have even crush, all the way around. For that to happen the case spigots have to be deadnuts level and exactly on the same plane, the jugs have to be deadnuts the same ht., and the heads have to have the same level of precision as the case. Having decked over 150 cases over the years and seen how wildly uneven the spigots have been all but one (a low mileage 911 case) I can tell you the likelyhood of success of all 4 laminated gaskets on an old, undecked case (or an improperly decked case) is bleak. Next, at operating temps the clamping has to be perfectly even and the expansion of of both chambers in each head has to be the same for that to happen. This is rarely the case. Shuffling of the heads on the jugs frets the gaskets. Frankly I consider it a miracle that any of them make it. I feel like Clay's success probably stems from careful builds, good tuning and frankly speaking some luck, unless he did all his machine work, too. (IMG:style_emoticons/default/biggrin.gif) |
Lo-Fi Version | Time is now: 27th September 2024 - 08:24 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 ... |