Help - Noob Valve Adjustment on 1st time engine build
 

Hi -

I'm running into trouble on the valve adjustment on my 3.0 motor during the final stages of my rebuild. I'm looking for help from the collective wisdom of this group.

I'm in the final stages of my "rebuild" on a '81 SC 3.0 motor. It's 100% stock and I'm reusing everything without machine work as (SC cams, stock P/C, etc...) I only had to replaced lower headstuds on a what was otherwise a strong running motor.

I have already set the cam timing per Wayne's book, re-installed the rockers and am performing the valve adjustment using the technique outlined in Wayne's book and on the forum (Grady Clay) starting with TDC for #1, adjusting both intake/exhaust then rotating 120 degrees for the remainder of the valves 1-6-2-4-3-5.

Using this method I have no issues with #1 and #6 however when I rotate another 120 degrees for #2 (and the subsequent valves) I find that either the intake or exhaust valve is open during the procedure. I'd expect both valves to be closed and in the "off cam" state so I can do the adjustment.

What is going on? Are my cams timed incorrectly? I know I must have missed something but I can't seem to figure it out.

I have double and tripled checked that I have the right and left cams installed on the correct side and that I timed the cams starting in the correct position with the "930 mark" and Z-mark on pulley in the 12:00 position.

About me... I'm not a total idiot (although I feel like one) but this is my 1st 911 motor. I've rebuilt 356 motor and a 901 trans and have done a bunch of other work on my car so I have some experience turning a wrench.

Many thanks in advance!

Well, I think you avoided perhaps the most common mistake - getting the right cam 180 degrees from where it should be. Easy to do if you set the left, then go off and do something else. This is the kind of mistake you soon discover as you keep installing rockers, because you will end up not being able to torn the engine over through 720 degrees - a valve will interfere with a piston. So that's good.

And you confirmed the L shaped cam is on the left bank, and the R (rabbit) shaped cam - the one where the intake and exhaust lobes are almost right in a line - is on the right bank.

So I don't know why starting with #1 at the TDC firing position, setting intake and exhaust lash, going to the next in the firing order, etc, won't work.

There isn't all that much difference between TDC firing (where you need to be to set lash) and TDC where the exhaust is almost closed, and the intake has just opened a bit (overlap, where you set the cam timing based on getting intake lift within spec). But I wouldn't suppose you started off with setting all the rest of the rocker lash upside down, so to speak? You had to set the #1 intake lash at the right place in order to time the left cam, and ditto for the right cam.

But the bottom line on setting lash is the base circle. For any rocker, as long as the rocker is on the nearly 180 degree wide base circle you can set it. With the engine on the stand you can just find - by looking or a little rocking of the crank - which rockers are on the base circle. Adjust those, then turn the crank 120 or so degrees, do some more, and once again and do the rest. Of course, after that you'd turn the engine several times, watching things to be sure you didn't miss something. Once you've set the lash, you can just wiggle the rockers to confirm they are right - one which won't wiggle will stand out, as will one which wiggles way too much.

With the engine in the car, you can set all the valves by rotating the engine, I think, only twice? This is mainly helpful in only having to get under the car twice (maybe three times, I forget). The "adjust valves in pairs by the firing order" has a lot going for it in terms of keeping track of where you are and not missing anything, but it isn't the most efficient method.

No doubt you have looked, many times, at a diagram showing where #1 is, and where #4 is? I forget, but did VW (and 356) do it differently?

Thanks Walt. I appreciate your help.

The 356/VW has the same numbering order but unfortunately doesn't have OHC so this is my first rodeo in cam timing. I'm really missing pushrods right now.

I'm really focusing on the basics as I suspect it's either I have the cams swapped or they were off phase when I was setting the cam timing.

Let's review the most basic stuff....

1. Which side is the Right vs the Left? I assume that the "rabbit ears" narrow cam is on the Right or US Passenger side and the wide lobed cam is on the Left or US Driver's side. Is this correct?
2. When setting the cam timing, I started with the pulley, and both cams with Z1, and 930 marks in the 12:00 position. The cam pins were installed so the cam gears were locked. I then followed the procedures in Wayne's book to set the timing starting with the left cam then the right one. My timing chains were tight as I used the Stromski chain tensioner tools. Is this correct?

Frankly it doesn't make sense to me unless maybe I'm not working with stock SC cams - maybe the prior owner upgraded them to a different grind. Would this explain the valve adjustment issue?

Interesting thread.. everything you say sounds correct. What intrigues me is that you say that you can adjust cyls #1 and #6 ok, but only have a problem when you get to #2. Seems strange that both valves would be closed for #1 and #6 but then be partially open when you get to #2?

This might sound like a silly question, but are you working from the rear of the motor, or the front? Any chance that we are not referring to the cylinder #'s correctly?

You have the cams in correctly. You can't run wild cams in a CIS engine - the 964 is as far as one goes. Hotter cams have more intake (and exhaust) lift at TDC overlap, so setting with a 1mm intake lift instead of a 5mm lift would screw up the timing and performance, and maybe lead to valve clearance problems, but it wouldn't lead to what you have here.

So I'll sort of ramble: both cams installed with the keyway up. Both cams pinned and nut (or bolt) tightened some. #1 intake rocker installed, and clearance set at 0.004" or mm equivalent. Dial indicator set up on #1 intake, and crank rotated 360 degrees. Indicator read, and you use your favorite process to fiddle around with the cam timing vernier system until you end up with the lift you want (somewhere around 1mm). Lock the left cam down. When done, the left cam should still be at about TDC overlap. If not because it moved some while you were doing all that tightening, just move the crank back so the Z1 mark lines up with the case halves or the mark on the fan housing, where it was when you got an acceptable number on the indicator.

In practice, most will spin the crank several times to confirm that at the Z1 mark the indicator continues to read what you want. But then leave it there.

Without turning the crank more, install the #4 intake rocker and set its lash. Since you never have two cylinders firing at the same time, the twin to #1, which is #4, will be 360 degrees out of phase with #1. Go through the setting sequence for the right cam, etc. That should have the left and right cams in phase with each other.

When you set the #1 intake lift/cam, as you watched the indicator as the pulley started approaching TDC, the indicator started to move from zero to -0.001, -0.002, etc? I think I once got this backward somehow. I see Wayne recommends setting the indicator with some pre-load, but that is probably kind of automatic - you just zero the indicator, which will be pretty far pushed up with the valve closed.

Let's ignore the right cam, and the exhausts. If you have #1 intake set as part of cam timing, and spun the crank 360 degrees to recheck the #1 lash, turn the crank, install the #2 intake (if it isn't already installed). Turn the crank 240 degrees, which should be the firing position for #2 if I have that right. You should be able to set the lash on #2. If 1 is right, 2 has to be also.

I don't think there can be such a thing as a twisted cam - they are too brittle for that. The engine ran with what you have.

I assume that you had the rocker adjusters pretty loose as you installed the rockers - you can't get the rocker shaft in otherwise anyway.

Somebody who has assembled engines in the 100s instead of the 10s or so may spot your problem for you.

Again, look for the base circles. They can pretty much tell you what part of the cycle each cylinder is in. And installing the distributor, and setting it so the rotor is on #1 when both #1 valves are closed at TDC, is yet another way of checking to see that everything is in sequence. This should allow you to check that the right and left cams are in the proper relationship.

G,

How can clearance for #4 be wrong? You set it when timing the right side cam, didn't you? Note the procedure in Walt's description for setting up #4 to time the right side cam.

Update!

Walt, Mike and Steve thanks for taking time to help out. Your combined input really helped me step through the entire process again and think this one through.

Good news and bad news! The good news is that i figured it out and everything is fine (cams, timing, etc). Bad news, it turns out that I AM an idiot. I had my math screwed up and what I thought was 120 degree pulley rotations was actually 240 degrees. This explains why everything was out of phase as I continued to rotate the pulley.

I guess working on my Porsche projects late in the night during the week when I'm tired caught up to me. It's Sat morning right now and I'm much less dumb.

Thanks again and sorry for the fire drill guys.

Glad you figured it out. It's easy to get out of sync.

These are photos of measuring the sprocket offset, but note markings:

firing order chalked on the floor
color coded pulley marks: Green = Geometry (0, 120, 240 degrees). Red = ignition
chalked numbers on pulley indicating what is TDC at each (1&4, 6&3, 2&5)

http://forums.pelicanparts.com/uploa...1553954524.jpg
http://forums.pelicanparts.com/uploa...1553955107.jpg

This is my way of cross-checking.

I suppose a guy could have too many references, but they help. I like Wayne's book a lot, but I also refer to Bruce Anderson's (RIP) book - it is well worth having in one's library. Bruce, in the 911 Performance Handbook, has a picture of the crank pulley. Written on the pulley by the mechanic or owner in chalk or something are the relevant cylinders: 1 and 4 at the Z1 mark, 2 and 5 at the 120 mark, and 3 and 6 at the 240 mark. 78SC's second picture shows this. This might have helped you keep track of what you were doing.

Like 78SC, I also have the firing order written in a handy place whenever reassembling one of my engines. Having done it a time or two gives you the confidence that you can do it, but relying on memory for a sequence of numbers is iffy. When I raced a VW in the Carrera Panamericana in 1991, the mechanic/co-driver of a real Porsche 550 (maybe a quarter of a million dollar 4 cam engined car)asked me what the 550's firing order was. Huh? No, it is the same as your VW. At the time I knew that, and it allowed him to get the eight plug wires connected correctly (I had passed that car in a previous stage). Now, I'd look it up.

None of us guessed your mistake correctly. Perhaps if Bill Verburg had put his mind to it he might have: with both cams initially timed correctly, what would cause #2 to have an open valve or valves when the crank was rotated 120 degrees for lash setting? Not turning at all, but that wasn't likely. How about turning too much, which would be 240. What would be the state of #2. Bill once posted a diagram which allows you to follow along what is going on with each valve.
http://forums.pelicanparts.com/uploa...1553978883.jpg