Valve adjust question - no rocker movement

[jlynch1960]

All good pointers, although as I've said several times, I am correctly following the procedures and, notwithstanding the lack of a Z1 mark on the pulley, I absolutely believe that I am starting at TDC for No. 1 - rockers click and everything is lined up - distributor, pulley mark. I will check to see that No. 4 is not clicking when I get back to it. I always rotate clockwise 120* (that's where the next mark on the pulley lines up) and everything works fine but the two noted. I'm being pretty anal about this - made a diagram, noted positions, checked off cylinders as I went and re-rotated the crank 360* when I ran into the problem.

I did reread the cam timing chapter in Wayne's engine rebuild book last night and looking at the diagrams of valve clearances I got a better understanding of the differences in valve positions between TDC at the top of the compression stroke vs. the exhaust stroke. However, if I were TDC on the wrong stroke, it seems to me both rockers on a particular cylinder would be "frozen" not just one since at the top of the exhaust stroke both valves are slightly open (per Wayne's diagrams).

I also did some more searching and a fellow named Don Ivey started an identical thread back in 2010 that only lasted a couple of posts so I guess he figured it out. I've PMed him and asked what the resolution was for him.

Need to do some "real" work today so will try this again over the weekend.

Thanks for the help for now and I'll either be back with more questions or the answer to the problem. Love this board!

Jim

[ivangene]

there must be someone near you that you can invite over for a coffee or beer that will show you or confirm the "trouble"

put out an invite

[jlynch1960]

Well so much for Don Ivey's problem. He replied-

"Jim, the resolution was that I wasn't counting the degrees correctly from TDC on number 1cylinder. Somehow I was trying to get all six firing on one rev. of the pully, instead of the requisite two revs. Just go slow, start at the right place, and you should be fine. I felt like a real fool, but realized later everything was alright. Good luck, Don"

I'm going through two full rotations so that's not it.

As I said, I'll try again from scratch this weekend.

[hcoles]

Originally Posted by cgarr

Pull the dist cap and roll it around till the rotor is pointing at that cylinder, there should be a mark on the pulley near that spot then check the valves for that cylinder.

Yes, do this - assures you are at TDC and both intake and exhaust cam lobes are on the dwell section. Then check/adjust with feeler.

[CCM911]

You really need to stick a wooden dowel on the plug hole of the cylinder that you are adjusting. If the dizzy is pointing to the cylinder being adjusted, and the dowel is as far out of the cylinder as it can be, then you are good to go with the adjustment.

[hcoles]

I could be messed up but I think since the dizzy is geared 1/2 rate of the crank, when it points to the cylinder of interest the intake and exhaust are on dwell and not overlap and that cylinder is close to TDC, I don't see why the wood dowel is necessary.

[lindy 911]

The problem is that we are not sure the cams are timed properly AND the TDC (Z1) mark is not verifiable on the pulley. It's view is blocked by the outer accessories drive pulley. The only way to verify cam timing is to measure it with a dial indicator. At this point I think that's where we need to start so cam timing can be eliminated from the possibilities.

He says that the car ran fine before the attempted adjustment so I'm thinking the cam timing is not the problem. It also sounds like he's got the process down pretty well so I suspect that's not the problem either.

I ask again; at the point in crank rotation where there should be loose rockers, is the elephant foot on the lobe or the base circle (non-lobe part of the cam)? If it's on the base circle there is a dimensional problem with the valve and rocker. If it's on the lobe there is a timing problem.

[ivangene]

+1 for NOT sticking wood into your spark plug holes

[Quicksilver]

This may be the stupid comment/question...

You say this is the first valve job so are you pretty new to 911 motors?
The 911 counts the cylinder numbers different then more common V8s (or pretty anything else). Other cars have the cylinders numbered by crank position from front to rear. The 911 has them numbered 1,2,3 up one side of the motor and 4,5,6 up the other side.

So the question is: Are you really on #2 or are you on #4?

[911pcars]

Performing a procedure by the numbers is fine unless you miss a step. At that point you're screwed or at least confused.

The only purpose of going through the step-by-step procedure of starting at TDC is to ensure the valves are closed for the cylinder to adjust. Okay, but all you need to do is to verify each valve is closed before adjusting the rocker arm (valve) clearance.

To do this, merely observe the position of the cam lobe relative to the rocker arm. When the heel of a cam lobe rotates around and contacts a rocker arm, that valve is closed. Simple. Stop. Adjust.

Disregard all the text descriptions on this illustration except for the area at the bottom (base circle or heel).



You'll notice the base circle continues for a several degrees before the rocker arm reaches the clearance ramp at which point the lobe begins to open the valve. And since the cam is driven by the crank (btw, at half speed), the crank doesn't have to be exactly at TDC for the valve to be closed, just pretty much on the heel.

And to avoid physically moving back and forth between top and bottom of the engine (rotating the crank pulley/adjusting two valves, etc.), I would suggest connecting a remote start switch on the starter solenoid. "Bump" the engine to rotate the engine and thus each cam lobe into position in turn, then adjust. Repeat until all valves are adjusted on one bank; bottom left side valves, bottom right side, top left side, top right side (your choice).

Hope this removes the mystery of those "steps" which can get you through a procedure but doesn't necessarily provide insight to some important engine operating relationships.

Sherwood

[ivangene]

[jlynch1960]

To 911pcars reply - yes, on the two problematic valves I was able to rotate the crank to a random spot in the cycle that freed up the rocker (allowing it to click). I then made the valve adjustment for the problematic valve doing that. What I found troubling was that the valve wasn't in the "dwell" position (if that's the correct term) when everything else indicated that the cylinder was TDC. Should I not be concerned about this?

As to Lindy's reply in terms of observing the lobe vs. the heel, I can't say I can easily distinguish the two in all instances. If the lobe were perpendicular or nearly so to the rocker (or on the backside "closing" ramp) I think it would be fairly obvious and in this case it wasn't. However, if the ramp of the lobe were just starting to rotate under the rocker, I'm not sure I could tell precisely the difference between heel and ramp given how small the window of vision is and the fact that I'm working under the car, etc. Wish I had stuck a feeler gauge up the backside to check for contact or just looked at other valve positions away from the valve I was working on to give me some reference points.

As I mentioned, I'm going to take another crack at it this weekend and will post the results.

Again, thanks for the help!

[jlynch1960]

To the guys offering counting lessons, I have Wayne's two books, a Bentley's, a Haynes and I spent a couple of evenings reading through dozens of posts on the topic before I tried this.

Wish it were that simple, although that being said, I wouldn't be surprised if this resolved itself on something really stupid on my part. If that's the case, I'll say it now just to get it out of the way - I'm a %$^&* idiot.

Cheers.

[lindy 911]

Perpendicular to the rocker is all that's needed to adjust clearance. As long as the rocker is not on any part of the ramp or lobe, you'll be OK. My only concern is that if you follow the procedure by turning the crank in 120 degree increments, you should not end up with a rocker on the lobe that is to be adjusted...

[jlynch1960]

Sorry Lindy, terminology blunder - by perpendicular, I meant that the north/south axis of the lobe (the nose) was pointing at the rocker. If that's something other than perpendicular, my bad.

Lindy quote - "My only concern is that if you follow the procedure by turning the crank in 120 degree increments, you should not end up with a rocker on the lobe that is to be adjusted..."

Yeah, me too! If I were comfortable just adjusting the troublesome valve at some random location in the cycle that allowed the rocker to click, I wouldn't have started this thread. It's precisely because something seems out of whack that I'm concerned.

[T77911S]

Originally Posted by jlynch1960

I've re-rotated the crankshaft three times to the 240* point on the distributor which lines up with a mark on the crank pulley. (I cannot locate a Z1 mark on the crank pulley at 0* - if it's there (3.2 Carrera) it is obscured by the AC compressor pulley.

As I understand it 0*equals TDC for #1 and #4, 120* is #6 and #3 and 240* is #2 and #5. O* is under the #1 spark plug wire and the notch in the distributor at that location points toward the fan. Each of the distributor locations (obviously approximate for 120* and 240*) lines up with a mark on the pulley.

?

are you trying to line up 0,120 and 240 on the distributor? if you lined up the dist to 240 degrees, that was for #3, not #2.
you only use the distributor to find the compression stroke/TDC for #1. after that, all the referances are done at the pulley.

another possibilty is that you either missed a timing mark or you referanced the 30 degree ignition timing mark.

how did the car run before you started?

i strongly suggest buying the little tool for doing the valves. i tried it with a standard set of gages and it just does not work. i also find it is harder to get a good adjusment buy backing the adjusting screw out, then trying to "start from scratch" and get a setting.

i use the angle of the screw as a reference. if it is too tight, i note the angle, losen the the nut(i will actually turn the screw and nut together, never completely losening the nut), noting the new angle of the screw and tighten the nut making sure the screw angle does not change, then re-check the gap.

if i have to tighten the screw, i losen the nut just a tad, then as i tighten the nut, i turn the screw with the nut.

you really need the tool. once the valves are set, you need to rotate the engine several times then go back and check them again.

[911pcars]

The key step in making sure subsequent steps get you to point B is to begin with no. 1 cylinder at TDC ready to fire. Assume this is not an engine just assembled (perhaps timed incorrectly) - it is already an operational engine.

The corresponding marks on the crank pulley and case must be aligned AND the distributor rotor must point to spark plug wire no. 1. If these two items are in synch, the valves for no. 1 cylinder are closed and can be adjusted for clearance.

However, if instead you begin no. 1 at TDC overlap position (intake valve opening/exhaust valve closing), then all subsequent steps will also be off. You'll also notice the rotor instead points to cylinder no. 4 spark plug wire.

From the correct starting point, subsequent crank rotations of 120º will position the next cylinder in the firing order to TDC - ready to fire (check rotor position) and so on. Per the step-by-step procedure, after two complete crankshaft revolutions, you will have adjusted all 12 valves.

A bright work light aimed into the work area helps ID the relative parts in question.



Hope this helps,
Sherwood

[lindy 911]

jlynch,

The illustration from Sherwood shows the lobe pointing away from the rocker. This is the correct position for then adjusting the clearance. If you are following the steps correctly and are getting rocker contact on the ramp of the lobe (or on any part of the lobe) there is something wrong with the timing of the cam. That can be easily checked with a dial indicator and the Porsche holding tool. It's not easy to adjust the cam timing with the engine in the car but checking the timing is easy. I would do this first and eliminate this as a possibility.

The pulley can only go on one way as it is positioned with a pin into the crank. It can walk a few degrees either way of 0 degrees but not enough to cause your problem.

[Kevin Stewart]

pull the valve cover and see if the cam is broke, Kevin

[lindy 911]

That's a good one Kev...