First 911 Valve Adjustment - Questions

[vesnyder]

OK - I pulled my engine last week and started the valve adjustment. Having done several on my 914, I am not a total neophyte when it comes to this. When I started I noticed that many of the current valves had no gap whatsoever. On several of the valves I had to turn the set screw a complete rotation before a gap appeared? The car seemed to run OK and it has been almost ten years and 8,000 miles since they were adjusted.

Just wanted to run this by the board and see what you guys thought. I will be checking them three times but something does not seem right?

[hcoles]

doesn't sound right, look to see that the rocker pad is on the middle of the cam base circle

[Ronnie's.930]

My guess is that you don't have said cylinders squarely on TDC . . . verify with crank pully and distributor rotor orientation.

[psalt]

Vance,

The wear pattern is for valves is to close up over time. The idea that "noisy valves just need adjustment" is usually incorrect and chasing noise by closing gaps is a mistake. The purpose of the gap is not for thermal expansion, it is to allow the valve to sit down long enough to give off heat. Since the gaps increase when the engine is hot, it is possible for an engine with zero clearance to run OK, but the exhaust valves will have a short life and recede at a higher rate. My advice is to set the clearances on the high side and do a leak down test. If the seal is OK, check them again after the engine has been run a while. If the gaps close down again after a short time, the valves have been burnt.

[Bob Kontak]

I am in Kent, Oh right now. Let me know through a PM and I can come out and get you going in the right direction.

Please, I got time. I seriously want something different to do. I am remodeling bathrooms and I need to come up for air.

[ivangene]

Awesome offer Bob !!
as stated the can get tighter over time so no gap is not unheard of, but best to check with someone with experience before assuming...

since the motor is out its easy to do, you guys will have it done in no time....

[Gustyones]

I've only done one valve adjustment so i'm no pro. I agree with Ronnie's.930 that you may not be at TDC. I really struggled with this on my first go at it. I'd take Bob up on his offer and the process will be MUCH easier if you have someone to walk you through it.

[Bob Kontak]

Vance is cooking now. One minute to nail down the firing configuration and ten minutes yakking about cars.

Nice talking to you Vance. Call anytime.

[vesnyder]

Bob - You da' Man! I was looking at the firing configuration upside down! Duh?? I will be sure to go through them three times. If I have trouble when the engine is on a stand imagine if it was in the car!

Thanks again!

[ivangene]

hopefull when the motor is back in the car the "upside down" thing will be all worked ou

[island911]

just make certain that the valve that you are adjusting is not 'on lobe' ...which can be seen when turning the engine. (if it's not moving, it's off-lobe . . and you can usually feel the gap . .and often feel if it's wrong, after you get the feel of a few of the right gap.)

Then remember that the gap spec is .004" Plus or Minus .002" (read: the gap setting is not hyper precision)

[Ronnie's.930]

Originally Posted by island911

just make certain that the valve that you are adjusting is not 'on lobe' ...which can be seen when turning the engine. (if it's not moving, it's off-lobe . . and you can usually feel the gap . .and often feel if it's wrong, after you get the feel of a few of the right gap.)

Then remember that the gap spec is .004" Plus or Minus .002" (read: the gap setting is not hyper precision)

Where did you source the plus minus .002? I'm curious because this is standard practice with Ducati and other non-hydrolic systems but I could not find this info for Porsche (maybe in the factory manual - which I don't have) . . . I ran a thread asking about this recently . . .

[island911]

Found it on a factory decal on the underside of my SC deck-lid. ...among other places.

For a little background on me; I made some rather cool and popular valve adjustment tools for quite a few people on this board a while back (circa 2004). (read: I was very aware of valve adjusting methods/ subtleties) However, I soon found myself not even needing the tool that I had designed to work so well. Reason being, First, as I've said above, one can quickly get a feel for the proper gap (again noting that the tolerance is as big as the gap) And secondly, simply watching the adjustment screw angle (turn from just touching to about 1/8th turn -iirc) was good enough (well w/in tol.)

[Ronnie's.930]

It's nice when the "mechanic's feel" happens! I've had similar experiences setting the valve lash on Ducatis over and over and over for race applications (same with the timing belt tension) got so I didn't really need the feelers or tension tool - a friend of mine refered to this as my "calibrated finger" . . . will have the Porsche calibration down soon. I'm using the "backside method" - I really prefer it so far . . .

[vesnyder]

Question regarding process. I was told that two cylinders can be adjusted without rotating the motor to the next notch. So when adjusting cylinder #1, cylinder #4 can be done, cylinders #6 and #3, finally #2 and #5. Is this accurate? This is in lieu of rotating the engine twice; once for cylinders # 1,6 and 2, and the 2nd rotation for cylinders #4,3 and 5.

Thanks!

[Bob Kontak]

The more I think about it the less sure I am that I was correct on the sequence I told you regarding which two cylinders can be adjusted at the same time. Someone else will be able to clarify.

For default. Adjust #1 at tdc. Spin it manually a couple of times (720 degrees) and re-check your gap(s). If you are happy, move to #6 which is 120 degrees past tdc for #1 and repeat.

If you want to stay on one bank (rather then spinning the engine around on the stand) just use the 162435 sequence and rotate 120 degrees past #1 tdc (120 degrees for each cylinder) to align to the cylinder you choose.

Edit - When #1 is at tdc #4 piston is at the end of the exhaust stroke and beginning of the intake stroke. Both of #4 valves would be open so I was wrong. Just stick with one at a time. Sorry.

[Bob Kontak]

Originally Posted by island911

just make certain that the valve that you are adjusting is not 'on lobe' ...which can be seen when turning the engine. (if it's not moving, it's off-lobe . . and you can usually feel the gap . .and often feel if it's wrong, after you get the feel of a few of the right gap.)

I think you mean if it IS moving, it is off lobe.

Vance has backed some of his adjustors off several turns so he has to look at the lobes on the valves to make sure.

It is amazing how adept your feel gets after doing a few of them. I use a metric dial indicator with the P207 holding tool and I got pretty good at guessing within a few hundredths of a mm when they felt close to the right tolerance before adjusting.

Post #63 has a picture of the + - 0.002" tolerance decal for an 87.

Temperature effect on valve adjustments?

[hcoles]

you might be confused by all the tdc, bdc, overlap, rotor angle, firing stroke, pulley marks/etc. time to revert to the basics.
Look at where the rocker pad is touching each cam lobe before you adjust, get the rocker pad contacting the cam lobe near the middle of the red line area (a.k.a. dwell section) and then check and adjust the lash. Do one rocker at a time.

After you get used to seeing how this all works, in the future you will confidently use some of the time saving methods.

[boyt911sc]

Originally Posted by vesnyder

Question regarding process. I was told that two cylinders can be adjusted without rotating the motor to the next notch. So when adjusting cylinder #1, cylinder #4 can be done, cylinders #6 and #3, finally #2 and #5. Is this accurate? This is in lieu of rotating the engine twice; once for cylinders # 1,6 and 2, and the 2nd rotation for cylinders #4,3 and 5.

Thanks!

Vance,

Take a look at the chart below and visualize the crankshaft pulley's orientation during the firing order:

Valve #...............Deg. Rotation
(firing order)
1........................ 0 deg @ Z TDC (Dizzy rotor point @ scribed mark)
6........................120 deg.
2........................240 deg.
4........................360 deg. (1st. complete revolution of pulley/crankshaft)
3........................480 deg.
5........................600 deg.

1........................720 deg. (2nd. complete revolution of pulley/crankshaft)

After 2 complete rev of the pulley, it is back to its original starting point. And it takes 2 crankshaft revolutuions to one (1) camshaft rotation. So adjusting the #1 & #4 valves simultaneaously will not give you the correct setting for valve adjustment. One nice show & tell guide is using the distributor rotor's position during valve adjustment.

Tony

[vesnyder]

Thanks guys. Two crank revs to one cam rev - I knew this but got confused. Even though the crank and pistons are in the same location after one rotation the valves and cams are not. I have it now!

Bob - Got your v-mail. Thanks for following up.

Tony - Thanks for the table. That is helpful.