Howto adjust cam timing, timing advance ??

[Flat6pac]

Walter, You and I are long past being novice at this, but youre always so eloquent in your discriptions...
Bruce

[efhughes3]

It should also be noted on the newer cams with the bolts in lieu of nuts, it takes a little experimentation and compensation to do this, as there is no way to really hold the cam steady, and the valve pressure wants to move it. It will become obvious to you what is happening, and intuition will tell you how to overcome it.

[LeakProof]

You guys have prepped me well.

Hopefully my Torco cam lube will arrive tomorrow. ( I know, no molly)
And then I could get started on the cam timing.

I purchased a dial indicator from Harbor Freight for $15.00, all stainless steel, Made in China. Surprisingly the construction seems very nice.
The only problem is that it does not fit in to the z-block. (bummer)

So I went ahead and got the one from our host, now I have two, inch and metric.

The one from our host is plastic, but the case is cool, it's metric and it's made in Germany.

And what is that gray paint like substance on my rebuilt cam?
Not to worry, I did not remove it.

Leakproof.

[Walt Fricke]

I always used an inch indicator, because they are pretty inexpensive, and the millimeter ones seemed to cost a very disproportionate amount more. I've never been able to figure that one out.

But my latest toy was an electronic digital one, where I could switch from mm to inch, etc. I do just enough stuff to justify (to myself, anyway) buying one for maybe $75. And no counting of revolutions.

An issue with many of these indicators is getting an extension for the indicator (the long skinny silver rod) so it will reach down deep enough to hit the spring retainer and go far enough down (which isn't all that far for stock cams). When I purchased my Z block and first indicator (before Pelican came to be), that catalog Porsche parts company also sold an extension. So the tip of the indicator unscrewed, and could be screwed back into the extension, and the extension screwed into the main part.

I then acquired some other indicators, including the digital one. But their rod parts had different threads for tips and extensions! Aaaargh. And didn't come with extensions. So I purchased a kit with all kinds of tips and extensions, and guessed right - they fit.

If Pelican sells an extension, or an indicator with a long enough rod, all is well.

For reasons I can't quite recall, I slip a 10mm nut onto the stud as a spacer before I put the Z block on. I think that, while the standard indicator rod was a bit too short, the extended one was too long. So this was a simple solution.

All in all, I'd say this is kind of the fun part of things. Installing and setting the rest of the rockers is just drudgery.

[efhughes3]

I think it is Mr Machineshop.com where I got my dial indicator very economically in a case with every kind of tip and extension you could ever want.

[LeakProof]

All timed!

Man that was insane, it took me a day and a half, to get the cam timing right.
All because, of the way I installed my woodruff key's, by using the sprocket flange, and the cam nut, to seat those buggers. So there for, one sprocket flange didn't seat all the way, and I didn't figure it out for several hours of frustration, why I couldn't dial in.

I new the cam nut didn't look quite right, so finally I got smart and torqued it some more, and then it set.

All of a sudden I was able to dial in the desired timing.

1.7 with carrera tensioner's installed (no oil pressure of coarse)

When tessioner's are oil fed, the tension should increase, getting me closer to 1.0

My main concern is,. how I installed the woodruff key's. I hope there not cockeyed in there.

What do you guy's think about, how I installed the key's? At first, I thought this method, was pretty clever and the only way possible to seat them.

Now, I hope I didn't screw anything up.

Leakproof.

[Walt Fricke]

Whoa there, hoss.

My take on Leaky's Woodruff key is here: 911 Fitting woodruff key to camshaft (I can't figure out how to link to this, though it has to be simple as I see it in other posts), so I think he is OK there.

But I think it a mistake to believe that pressurizing the chain tensioner will cause the cam timing to change. When you time a cam you want quite a bit of tension on the chain. This is normally done by forcing the idler wheel up mechanically, using any number of clever expedients, so the chain is quite tight - no slack as such, and can only be picked a little bit up off the plastic ramps.

In operation, the run of chain which is not running over the idler gear is under constant tension as the gears and chains are pulling against the numerous valve springs. Making things taught when setting the timing mimics this, so the crank and cam are always in the same relationship as initially set. Since setting timing is a static, rather than a dynamic, operation, you can't count on valve springs and rotation and whatnot to insure that the tension side of the chain is taught. So you need to tighten it when setting.

The spring in the tensioner provides most of the slack removing in the system. The oil mainly serves as a shock absorber, to keep the chain from vibrating too much, so to speak. Guys who have run engines with the chain cover removed say it is fearsome to watch.

I think the oil in the tensioner adds some to the tension. As the chain loosens (while vibrating), the spring pushes the plunger up, and oil flows through a one way valve and fills in behind the plunger. Now the chain has to push that oil out of the way as well as overcome the spring pressure if it wants to push the idler wheel away. Like a shock, the oil will move, but reluctantly. Hence the damping effect. But the oil pressure is not the main thing for keeping the valve timing constant. Otherwise you'd get different effects depending on engine oil pressure and different oil viscosities and temperatures.

Wayne's book shows a method or two of applying the needed tension. Someone recently posted a cheap and clever way with nothing more than a nut and bolt.



You will note he didn't even install the tensioner at this point. I think that is the norm, though it can be done with the tensioner in place.

I bet a search would show up quite a number of things guys have made or used to do this. I use a small tool you can purchase, because when first I started doing this I didn't fully understand and thought a special tool (not too expensive overall, though a bit pricey considering alternatives) was needed. But I don't regret the purchase, it is small, and I use it every time I do this.

I have never experimented: set with just tensioner spring tension, then tighten up the chain and see where the dial needle ends up after you rotate the crank again. Maybe someone has done this and will chime in. It might be pretty close, though I have never seen anyone advocate using just the tensioner for this purpose.

What I know I have not seen (not that I see all) is a standard figure: tensioner tight only minus X = running setting. You are assuming X = 0.7mm. Where did that come from?

Anyway, I think that unless you are comfortable running with the 1.7mm timing you measured you ought to do this over. Much easier now with the engine out of the car. And you are now an old pro at setting the timing. An hour should do it.

Plus you can slip that one flange off to verify where the Woodruff key is.

[LeakProof]

Thanks again Walt.

Now would be the time to correct this and take a look at those woodruff keys.

Would running 1.7 be to risky? I'll put the vice grips on the idler arm to increase tension (like I did in the first place) and see were the guage ends up.

I really thought this method (other means of tension) was a little in- accurate, the way the needle moved around depending on the type of tension.

All it took was my finger lifting a little on the chain to get closer to 1.0.

And every time I loosened the cam nut and re snugged, the setting changed a little.

One other interesting note. The Service Manual shows the timing being done with just the carrera tensioners installed.

I know, nobody does it like this, probably for good reason.

I'll have to decide were to go from here. Tell you the truth I'm more worried about the woodruff keys sitting perfectly, then leaving the 1.7, knowing it's in spec and should come down possibly with chain strech and hydrolic pressure. Perhaps the issue is how I arrived to 1.7.

I think perhaps, I'll go check things again. Could actually be less then 1.7. Would it hurt the engine running it like this? Would this be considered advanced?



Thanks,

Leakproof.

[juanjose]

I'm trying to set my cams at the same timing and the left cam is at 1.7mm and the right cam the closest I can go is 1.63mm.
Any ideas?? May be move the sprocket on a different position on the chain??

[juanjose]

Sorry My engine is a 1986 3.3 turbo with sc grind.

[Flat6pac]

Youre with in the spec of .1
Bruce

[Walt Fricke]

Bruce is hinting at this: Why bother?

But if you really really want the brain damage of getting closer, despite being within the factory tolerance, you will have to move the vernier pin. My experience, anyway, is that the end of the adjustment with the pin in one hole overlaps the other end of adjustment with the pin in an adjacent hole. Don't ask me which is which. And, with your bolt end cam it appears that these fine adjustments, which are just barely possible with the older style big nut cams, are even more difficult. But moving the pin, if you are actually at the end of the pin slop, is what you will need to do to come closer.

0.1mm is 0.004". You are at 0.0037. I don't know if I have ever gotten my cams much closer than that. Maybe 0.002 if I got lucky. The factory system, with the pin, expects that the two will not be the same to within less than 0.1mm - the manual just says move the pin until you achieve that. It is we who time our own engines who have figured out how to come a bit closer using the slop.

Walt

[efhughes3]

The big bolt on later cams can be bottomed down on a collar and then one can adjust to their heart's content. Or, you can get a longer bolt and do the same thing, but the pitch makes it hard to find. I mentioned this and took a pic or two in my recent build thread "Ruby's rebuild rev2" or something thus.

The last time I overcompensated to allow the cam to roll back, but this took a bit of trial and error and was a bit tedious. The bottomed out bolt method was a lot quicker.

[HKZ Bob]

Originally Posted by lindy 911

1. Set the crank at TDC.
2. Rotate both cams so that the dot or the 930 is at 12:00 or straight up.
3. Insert the pin in both cam sprockets where it will fit.
4. Set the valve lash on #1 to proper clearance (.004")
5. Install the dial indicator on the intake valve retainer on cylinder #1 and pre-load it.
6. Zero the face of the indicator.
7. Turn the crank clock-wise about 3/4 turn and look for the intake valve to start opening.
8. Continue to turn the crank until it is at Z-1 and stop.
9. Loosen the cam bolt and remove it, the big washer and the stake pin.
10. While making sure the crank stays at Z-1, rotate the cam until you observe the proper lift on the dial indicator (1mm in your case).
11. Replace the stake pin in the hole that lines up along with the cam bolt and big washer.
12. Rotate the crank at least eight times around and re-check the dial indicator. It should match the 1mm reading you set it to at TDC.
13. If it matches after turning the crank eight times, stop at TDC, remove the indicator and repeat the timing for cylinder #4.

The main idea is that the intake valve is starting to open as the exhaust valve is closing as the piston is approaching top dead center. The timing of this sequence is critical. You want the intake to be 1mm open when the crank is at TDC on the overlap stroke. Note that you should only have rockers installed on intake #1 for the left cam and then intake #4 for the right cam AFTER you set the left.

Hope this helps.

Lindy

Hi Lindy

on line 3 the you mentioned insert the pin.

on line 9 you are saying stake the pin. Does it means you are removing it under at Z1 mark and then try to insert it again. Will the cam move to find another insert point?

BR
Bob