Yet another valve adjustment thread (dial indicator method)
01-03-2012, 10:52 AM
#34
Racer
Join Date: Oct 2011
Location: sta. clarita calif.
Posts: 338
Likes: 0
Received 0 Likes
on
0 Posts
Ricardo, there is a very interesting article by Doug Riley over on Pelican website that explains the "Backside" method of 911 valve adjustment. If you hit the Tech articles section for 911's and scroll down to the engine section you'll find it. I don't know if it appertains to 964's or only the older 911's, but to my limited valve adjustment experience (356's) the mathematical theory should(?) apply the same. If you've got some spare time to locate and read the article I think you'll find it very interesting. Apologizing in advance if its old news to you. CHEERS.
01-06-2012, 10:03 AM
#37
Z-Block
It's roughly 45mm tall, 40mm wide and 20mm thick.
The top and bottom are 30mm wide and 15mm tall.
The upright is 20mm thick.
The holes are 10mm and 10.5mm with the larger being the valve cover stud hole and the smaller the dial indicator hole with the set screw.
Note that the device would function better if the stud hole were a slot as some of the valve cover studs do not align correctly for the given hole centers. As I recall there are two valves that can not be checked via this device, though I've forgotten which ones.
The top and bottom are 30mm wide and 15mm tall.
The upright is 20mm thick.
The holes are 10mm and 10.5mm with the larger being the valve cover stud hole and the smaller the dial indicator hole with the set screw.
Note that the device would function better if the stud hole were a slot as some of the valve cover studs do not align correctly for the given hole centers. As I recall there are two valves that can not be checked via this device, though I've forgotten which ones.
01-06-2012, 02:57 PM
#40
Rennlist Member
Thread Starter
A definite yes on the slot for the Z-block. The upper valves do not align perfectly. There is another approach as well that I want to try next time with dial indicator swivel clamps and rods. I think that would allow for a huge range of adjustment. But sometimes more adjustment is worse. Slotting the Z block is the way to go. I am going to look into having that done to mine.
Great DIY.
01-07-2012, 12:42 AM
#43
Rennlist Member
I just completed the valve adjustment and plug change on my 93 C4. This is the second time I have adjusted the valves on this car (previous time about 16K miles ago). On the first job I used a combination of the small feeler gauge at the valve stem, the NineMeister Tool, and the "backside method" to build confidence and practice. I especially like the "backside method" from the Pelican post, because you can check the existing gap quite easily before making any changes. Using this method, I found that 8 valves were Good, one was Tight, 3 were Loose. On those requiring adjustment, I used the NineMeister Tool, and in one or two attempts brought the valve back into spec per the "backside method" check. For the backside method, I used 0.0030" as the "loose" spec and 0.0025" as the "tight" spec. The engine is a bit quieter, and seems smoother - but it may be my imagination.
Next project - same task on the 90 C4, perhaps this weekend. My wife will be SO confused to see another black Porsche scattered all over the garage, again, still.
Next project - same task on the 90 C4, perhaps this weekend. My wife will be SO confused to see another black Porsche scattered all over the garage, again, still.
01-07-2012, 12:58 AM
#44
Rennlist Member
Thread Starter
Finally read the backside method article which is here:
http://www.pelicanparts.com/techarti...alveadjust.htm
I love the go and no-go aspects of this approach. Where did you get your feeler gauges? I want to try this next time which may be soon as I am closing in on a 91 C2 Tip purchase in need of the 60k maintenance including a valve adjustment.
I see at McMaster Carr you can buy a 12" long loose feeler gauges for very little in the sizes specified, there is also the gauge sets that are connected at one end. Any recommendations on which to get? Loose may be better I think.
http://www.pelicanparts.com/techarti...alveadjust.htm
I love the go and no-go aspects of this approach. Where did you get your feeler gauges? I want to try this next time which may be soon as I am closing in on a 91 C2 Tip purchase in need of the 60k maintenance including a valve adjustment.
I see at McMaster Carr you can buy a 12" long loose feeler gauges for very little in the sizes specified, there is also the gauge sets that are connected at one end. Any recommendations on which to get? Loose may be better I think.
01-07-2012, 03:31 AM
#45
Instructor
I see the one's your talking about. I would definitely get the loose ones. Constantly shifting between gauges on the connected ones can get a bit tiresome. That and it gives you a bit more room to work with... less bulky.