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-   -   backside valve adjustment - my thoughts (http://forums.pelicanparts.com/911-930-turbo-super-charging-forum/390457-backside-valve-adjustment-my-thoughts.html)

sand_man 02-01-2008 07:37 AM

backside valve adjustment - my thoughts
 
So I thought I'd give the "backside" method a shot.

For the record, I've adjusted more valves than someone who doesn't own a shop, ever should!!!! I have always used the traditional method of the feeler gauge (with the special holder) in between the rocker adjustment foot and the valve stem. Over the years, I have developed the infamous "feel" that many say is hard to get. I have to confess, one thing I've always hated about this method, is often times, I can't get the feeler inserted to check or double check. Even with the special feeler gauge holder, it can be awkward. Many times, I'll just break the adjustment loose, insert the feeler and tighten it back up until I can get that "magnetic drag" like feel. In other words, I'm sure I adjusted some valves that probably didn't need it, only because I struggled to get the feeler gauge in place. Once the adjustment was made and I pulled the feeler out, I never double checked it other than to wiggle the rocker and see if the "clicking" sounded right (checking by "feel")....still some possible guess work.

Fast forward to the "backside". What I like is that by using a .0025" gauge as your "go" and a .003" gauge as your "no go", you can easily check your existing adjustment and double check your work if a valve was in need of attention. Slipping the traditional sized feelers in between the cam lobe and rocker arm is pretty straight forward from above and below the engine. The gauge either goes in or it doesn't...none of this climbing around the engine compartment like a ******* Hindu circus contortionist with arthritic hands and fingers to get that special feeler gauge holder inserted!

I'm not really sure how much time this method saves, other than in my case, keeping me from adjusting valves that might not have needed it. Valve adjustments in a nut shell aren't much fun...especially on the driver's side!! It is what it is.

A few tips:
  • Keep the spark plugs in until the adjustment is complete (if you plan to replace them). The engine is actually very easy to turn over by squeezing the belt around the alternator pulley while turning the pulley nut. Removing the plugs BEFORE a valve adjustment can dislodge carbon that might affect your results.
  • I usually jack up one side of the car so that any oil in the lower valve cover of that side will run back into the engine case.
  • I adjust all the valves on that side and button it up BEFORE lowering the car, and moving on to the other side. This is done by rotating the engine 240 degrees each time you are ready to move on to a different cylinder's valves. Normally you would rotate the engine 120 degrees if you are working from side to side.
  • I use the silicone re-usable valve cover gaskets (reddish/orange in color). I can't tell you how many times I've had my covers off and still no leaks...they have more than paid for themselves!
  • I also [[[GULP]]] re-use my hardware at least three or four times before splurging on new stuff! I clean it up with some brake clean, blow it off with compressed air, and it's good to go. YMMV!
  • When working on the driver's side valves, I remove the lower tin that runs along side the engine compartment. To make this piece of tin easy to remove and install, I have just enough hardware securing it so that it doesn't rattle or fall off. If I need a bit more clearance for my forearms, I'll sometimes remove the engine compartment fuse panel cover...be sure to disconnect the battery, in case a wrench or some other tool hits one of the exposed fuses you won't roast anything. Keep in mind, my car has no smog equipment installed so it's a bit easier to reach things. I have found that removing the intercooler provides no additional clearance. YMMV.
  • When installing the valve covers, I think the biggest mistake people make is in over tightening the the nylocs!! It doesn't take much torque. SEND THE GORILLA BACK TO THE ZOO! The upper valve covers almost never leak, so I just snug the nuts and call it done. For the lowers, same thing...I get all the nuts just until they bottom out. Then I go around and snug them up with a short handled ratchet. The silicone gasket should just be barley squeezing out if at all. If one of the covers and/or nuts leaks, just a little bit more all the way around usually fixes it.
  • I've never tried it, but I've heard that valve covers that are slightly warped can be put right by running them over some sandpaper that has been affixed to a flat surface like a piece of glass.
I hope this helps...give it a shot for your next adjustment.

Traditional valve adjust:
http://www.pelicanparts.com/techarticles/911_valve_adjust/911_valve_adjust.htm
Backside method:
http://www.pelicanparts.com/techarticles/911_backside_valveadjust/911_backside_valveadjust.htm

turbocarrera 02-01-2008 08:58 AM

The backside method improved my life in many ways - it also compensates for a pounded rocker foot. ;)
Good write up. :D

JFairman 02-01-2008 09:13 AM

Nice write up.
Those ball jointed elephant feet pads on the adjuster screws will pitch sideways a little bit when trying to slide the special feeler gauge in there and make it annoying... takes patience and I usually run out of that while contorting myself in the process and decide it's quicker and easier to just loosen the things and readjust them too.

When taking the time to get the feeler gauge blade in there and check them I've found both the intake and exhaust clearences get larger with mileage so I set them on the snug side of .004" now.

I've never tried the backside method. Maybe someday.

sand_man 02-01-2008 09:59 AM

Quote:

Originally Posted by JFairman (Post 3741881)
When taking the time to get the feeler gauge blade in there and check them I've found both the intake and exhaust clearences get larger with mileage so I set them on the snug side of .004" now.

I think going too loose is a common mistake people make when using the traditional method. I have found that the feeler gauge should feel pretty tight when you have it under the adjuster foot.

AngM018 02-01-2008 01:38 PM

Great info! I am at 800 miles post rebuild, and I can already hear those rockers chattering. Looks like I will be doing my valves in the coming weeks. Still haven't decided on whether to drop the engine or not. I have heard the SSI exchangers are a PIA for valve adjustment.

les_garten 02-01-2008 01:43 PM

Quote:

Originally Posted by JFairman (Post 3741881)
Nice write up.
Those ball jointed elephant feet pads on the adjuster screws will pitch sideways a little bit when trying to slide the special feeler gauge in there and make it annoying... takes patience and I usually run out of that while contorting myself in the process and decide it's quicker and easier to just loosen the things and readjust them too.

When taking the time to get the feeler gauge blade in there and check them I've found both the intake and exhaust clearences get larger with mileage so I set them on the snug side of .004" now.

I've never tried the backside method. Maybe someday.

Hello,
Interesting that you note that your clearances get larger. I'm puzzled what would cause that? I was always under the impression that valves get tighter because of seat wear and get quieter.

Backside is the way to go. I'll never do it the traditional way.

Sand_Man, I have just one small suggestion. I went down and bought a new set of feeler gauges for this. I took out the two feelers .0025 and .003. On the .0025 I put a white zip tie, and on the .003 I put a Red Zip Tie. This way I could look at them and easily tell them apart very quickly. Mine eyes are getting older!

Les

Rob 930 02-01-2008 01:56 PM

For further discussion about valve adjustment by this method, and about my experiences regarding the validity of using a feeler gauge, you might check this thread on Rennlist:

http://forums.rennlist.com/rennforums/showthread.php?t=378903

sand_man 02-01-2008 03:08 PM

Quote:

Originally Posted by les_garten (Post 3742509)
On the .0025 I put a white zip tie, and on the .003 I put a Red Zip Tie. This way I could look at them and easily tell them apart very quickly. Mine eyes are getting older!
Les

EXCELLENT advice, Les!!!! Yeah...every time I picked up one of those damn feeler gauges, I had to make sure I had the correct one in my hand!

les_garten 02-01-2008 03:16 PM

Quote:

Originally Posted by Rob 930 (Post 3742526)
For further discussion about valve adjustment by this method, and about my experiences regarding the validity of using a feeler gauge, you might check this thread on Rennlist:

http://forums.rennlist.com/rennforums/showthread.php?t=378903

Hello,
Valve adjustment is a learned skill no doubt. All these methods work perfect if done correctly. The backside method makes it where you arrive at perfection quicker and with less frustration.

DonE, I didn't have to bend my feeler gauges, so I'm not sure I understand what you ran up against. I use straight, "standard" sized feelers. I stick the .0025 in there and leave it. I turn down the adjustment until I feel the adjuster "touch". I tighten about a third holding with a large stubby screwdriver. I check the feel of the .0025 feeler. If It's caught, I loosen up a little. I always watch the "clock" angle of the adjusting screw to help me determine how far to move the screw. When the .0025 is a tight drag, I pull it out and make sure I can work it back in. It should go in the gap, but be a little difficult to get in. If it is not tight going in, your lash is too loose. I check with the .003 to make sure it it is the "slightest" amount of loose. If I get a good tight drag, the .003 has no way of going in. This is the easiest and most accurate valve adjustment I have ever done on Porsche's.

As far as the Hot lash stuff on Rennlist. I think tjis is a non issue on a street car and a theoretical one on a Track car. All you have to do is have enough lash so that the valve seats and transfers heat.

Noisy valves are better than silent valves, ehhh?

Porsche designed these cars to be street cars in Germany. Which means sustained driving at well over 100 mph. I lived in Stuttgart in the 70's, believe me, you don't hang out in the left lane at 100 mph or less for very long. So the elves in Zuffenhausen figured .004 was enough to compensate for expansion due to heat with these bad boyz doing what they were meant to do on the Autobahn.

There's a ton of folks on this list with high HP 930's, who uses a lash different than .004?

Surely Stephen at IA would know about this?

One of the advantages of a Porsche in this regard is that we are all aluminum. A lot of a Porsche's engine parts expand and contract at similar rates, thus making clearances more predictable.

The backside method, at least to me has the advantage of being easy, repeatable, and consistent. Both methods must be verified. The traditional method makes verification a pain in the ASS. That's the real difference in the two methods.

just my .02

Les

sand_man 02-01-2008 03:16 PM

Quote:

Originally Posted by AngM018 (Post 3742502)
Great info! I am at 800 miles post rebuild, and I can already hear those rockers chattering. Looks like I will be doing my valves in the coming weeks. Still haven't decided on whether to drop the engine or not. I have heard the SSI exchangers are a PIA for valve adjustment.

AWESOME, John!!!! Your Grandfather would be so very proud!!! Drive that fucher!!!

Maybe Rarly or Ben can give their thoughts on valve adjustments with SSIs...shouldn't be too much different! Although my car without heat is pretty darn naked under there!

sand_man 02-01-2008 03:25 PM

Quote:

Originally Posted by les_garten (Post 3742665)
Hello,
Valve adjustment is a learned skill no doubt. All these methods work perfect if done correctly. The backside method makes it where you arrive at perfection quicker and with less frustration.

DonE, I didn't have to bend my feeler gauges, so I'm not sure I understand what you ran up against. I use straight, "standard" sized feelers. I stick the .0025 in there and leave it. I turn down the adjustment until I feel the adjuster "touch". I tighten about a third holding with a large stubby screwdriver. I check the feel of the .0025 feeler. If It's caught, I loosen up a little. I always watch the "clock" angle of the adjusting screw to help me determine how far to move the screw. When the .0025 is a tight drag, I pull it out and make sure I can work it back in. It should go in the gap, but be a little difficult to get in. If it is not tight going in, your lash is too loose. I check with the .003 to make sure it it is the "slightest" amount of loose. If I get a good tight drag, the .003 has no way of going in. This is the easiest and most accurate valve adjustment I have ever done on Porsche's....

...The backside method, at least to me has the advantage of being easy, repeatable, and consistent. Both methods must be verified. The traditional method makes verification a pain in the ASS. That's the real difference in the two methods.

just my .02

Les

PLUS 1,000!!!

les_garten 02-01-2008 03:49 PM

Quote:

Originally Posted by sand_man (Post 3742644)
EXCELLENT advice, Les!!!! Yeah...every time I picked up one of those damn feeler gauges, I had to make sure I had the correct one in my hand!

My eyes are so bad reading up close that I had to reach for my reading glasses each time, and about the time I hit the second valve set I had had enough!

Les

NathanUK 02-02-2008 12:47 AM

Those spanner sets with different colours for each size look pretty cool too. If I was a mechanic I would buy some if I was running my own business.

e170drvr 02-06-2008 08:24 AM

Sandman,
By jacking the car to one side were you able to adjust the valves without draining the oil? Or just to prevent drips with the oil drained? I have a couple of noisy valves from my last attempt that I would like to correct without turning it into a giant production with draining the oil that was just changed. Will also try the backside method, I suspect that my first attempt left the valves too loose, this was my first 911 valve adjustment, I guess I don't have the "feel" yet.

Eric
87 930

JFairman 02-06-2008 08:34 AM

If you have a couple nice big kitchen pots I think it would be easier to just drain the oil into them.
Then scoop it up in a clean coffee can or something around that size from the large pot and return it to the oil tank afterwards with a funnel.. rather than jacking one side, then letting it down and then the other.

Alot safer too.
A jackstand(s) under a tilted car is not a safe thing to get under... it could shift or slide off the stand and fall on you...

NathanUK 02-06-2008 10:00 AM

You don't want to get any dirt into the oil tank so be careful re-using oil that you catch. Remember that these cars don't filter oil first before it goes in to the engine like most cars do.

JFairman 02-06-2008 10:24 AM

I realize that :)
It's easily doable if everything is clean.

I've done it because I have to remove the braided B&B oil line next to the #3 cyl before removing and reinstalling my headers.

Also, any thing like small coffee ground sized coked carbon oil chunks from the turbo (they are there in mine from a previous owner) that may be sitting in the bottom of the oil tank or engine sump that come out with the flow of oil will sink to the bottom of the big kitchen pot after an hour...
I know because I've seen this, so it can be a good thing.

Just dont' do it outdoors on a windy day.

timc 02-06-2008 10:51 AM

valves
 
Quote:

Originally Posted by sand_man (Post 3741999)
I think going too loose is a common mistake people make when using the traditional method. I have found that the feeler gauge should feel pretty tight when you have it under the adjuster foot.

Yes, If you use the backside method, then go back and ck with the 004 using traditional method, you will be amazed at how snug it actually is, kind of scared me a bit.

tim

mb911 02-06-2008 11:07 AM

you gotta look at cgar's method best by all accounts.

1st snug adjuster up so zero clearance, back off 1/8th turn, dead on everytime..

pretty easy

les_garten 02-06-2008 11:24 AM

Quote:

Originally Posted by mb911 (Post 3751996)
you gotta look at cgar's method best by all accounts.

1st snug adjuster up so zero clearance, back off 1/8th turn, dead on everytime..

pretty easy

I kinda use a combination of both techniques. After adjusting a few valves and watching how much I had to backoff to get to the the .0025 measurement. I arrived at the same method as his, but I check with the backside feelers.

I still think you have to check it though. It is somewhat difficult to tell "exactly" where you are at zero clearance. You can have a "little" push on the valve if you are not careful.

Les


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