Howto adjust cam timing, timing advance ??
 

I am in the last process of completing my engine after a rebuild. I have the dial indicator and Z block.

Do I need to first adjust clearance for all the valve's first, then use dial indicatior for #1 and #4 ?

I have a 930 engine with updated SC grind profile 930 cams.
According to wayne's book, timing for 930 with SC cams is same as SC timing ???? Or any other suggestions/experience?

Is there anyone that has a nice procedure of how to set correct timing?
How do I use dial indicator?

You set the engine with the crank pulley on Z1
Cams are with the dot or 930 to the top then install the pin and retainer bolt or 46mm nut on both sides. Chains are inplace, cam gears, pins and bolts, and tensioners also.
Adjust the intake valve to .1 mm and load the Zblock and install the dial guage.
Pre load the dial guage about half way so there is tension against the valve retainer and set the outer rim to the end of the pointer for zero.
Cam spec is .9 to 1.1 mm with 1.0 being optimum
I prefer to shoot for the high side of the spec 1.1 because of chain stretch.
everything loaded, turn the crank pulley 360 degrees to Z1
This will cause the intake valve under the dial guage to start moving at about 30 or 40 degrees before TDC and the dial guage will move so you start watching the dialguage and the up coming Z1. This is the point you want the 1.1 reading to set. Remove the big nut and if you dont have the thread for the pin to pull, a top of a sparkplug will work.
17mm open end on the flats of the cam, pull the pin and find the hole near where the pin was to replace the pin for 1.1+ so you can get the pin in the proper hole for 1.1 and load against the pin in direction against the cam movement. If your 1.1 doesnt come in where you want it reload the pin. Anywhere is spec is is good, the high side is great but this is you working number for the match of the other cam. Lock your finished product, turn the crank 2 revolutions and you ll come back to the measurment on the dial guage you set.
Go to the other side #4 and set the valve.
Load everything again like you did on #1 and go through the same steps.
If you cant get really close to match the other side in the 1.1 mm setting you need to remove the tensioner and outer gear and move the gear in the chain one cog and put it all together.
This will give you all new measurments to look for and set to.
At this point your cam is near the desired setting, set the pin for the reading you want.
Pre load the pin and read the setting number.
Note, if you cant get into .15mm of the desired setting you ll need to move the gear inside the chain another tooth. You really want to be within a couple hundreth mm of the #1 setting
This might not be 100% clear but close enough to get the idea.
Bruce

Not sure if I understood completely, but I kind of did (i think)
Will adjust the valve clerance and mount up the dial indicator and try it out

I had some trouble understanding this procedure as well, but it finally sank in after a couple of shots at it. My dial indicator is not metric, so I had to understand what the numbers actually meant on the dial indicator.


http://www.mechanicalphilosopher.com/nocrow03.jpg


For me, 40 ticks equals 1mm.

Also, I was abit thrown off when it started going in the negative direction. I had to readjust the depth of the indicator to drop down instead of up as the cam rotated.

Once I got the dial indicator understood and properly secured, I set the engine back to TDC and put the dial indicator arm on the ZERO and started turning the crank. At about the 330 degree mark, the dial indicator started moving. I stopped turning the crank at 0.04" which was actually the 60 tick on my dial. Keeping the cam at that position, I removed the cam nut and pulled out the pin. then I moved the crank to Z1 and put the pin back in along with the cam washer and nut.

Now you just repeat the procedure for #4. keep in mind that 360 degree from TDC on #1 is actually TDC for #4.

I hope this helps, it was dreadfully confusing until I actually did it. you do have Waynes book right?

yups, reading in waynes book now to get the better understanding. :-)
thanks

Bruce. So I should go for 1.1 with my SC spec cam on my 930?

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

Thanks for feedback.
Think I get the understanding now. Was out in the garage and tried it out, seems like I need some adjustments. Will continue tomorrow.

Thanks guys for helping out :-)

Good read,..thanks.

Doyle

If you just have regular SC cam grind, the spec is for the cam .9 to 1.1. The cam is for Carrera
also and the Carrera gets loaded at about 1.5 in contrast, but that number is from memory instead of off the info as is the SC spec.
Bruce

930 engines have small ports. Therefor I'd advance the cams to the spec for the small port SC engines. This is about 1.2-1.5mm. This will give better torque at low RPM before the boost kicks in. High RPM power is not a problem with a 930 :)

-Andy

Think I forgot to mention that my 930 intake ports has been ported to 35mm.

Does this matter for my setting?
What would the best setting be?

yes, the needle goes in the CCW direction. just read the red numbers. DO NOT do like someone did mine. mine were suppose to be set at .020". they set them so the needle pointed to the BLACK .020, which was really .080.

I have a simple procedure (with photos) in my engine assembly handbook that may help you. Pretty sure you can download it now on the cheap and the photos are pretty good. It is only focused on assembly though, in a lot of detail, but no other info on disassembly, checking components, etc. You will find good "real world" info on 911 assembly.
Try the link below, or you can find it at my Scrogham Consulting site on Facebook (or through Synergy Racing):
Porsche 911 Engine Assembly Guide by Cole Scrogham in Reference

After reading Lindy's post, I like that method the best. Its much easier to simply spin the cam. Next time...ill know ;)

Perfect timing guys, on this subject.

I myself, will be setting cam timing this weekend.

Two things?

Bruce, are you saying that I should set the cam timing to 1.1 mm (the high end) instead of shooting for 1.0 mm (center) on my stock 906/06, 79 911sc?

Also, How important is it to get the cam (wave) washer centered. It seems like theres some slop here?

Leakproof.

Leaky

You don't need to get the big washer exactly centered, but what you do have to do is to be sure that none of its edges extend out beyond the cutout on the gear. When it is flattened out by the torque on the nut you want it flat on the gear. It can't do that if it is overhanging that lip. This is not hard to deal with - just be observant. And this is pretty close to being centered.

Walt

I always shoot for the high number but the truth be known you ll accept where the left number comes in and do your best to accept the right number.
Then there is always EXACTLY where the case center line and the Z1 mark is and how it it lining up. Line to line is a judgement call especially if youre getting frustrated with setting the second cam.
Bruce

Go to harbor frite and buy two digital dial indicators and get another z block. Then do the left, tighten nut 3/4 then do the right. Then you can forget about counting needle sweep revolutions.

Most times I have set cams it has been without the fan housing installed. I don't know if that is better or worse. You can use the case centerline as case TDC. That way you aren't relying on the housing, locating pin, and whatnot being spot on. On the other hand, the fan housing gives you a mark which is closer to the notch on the pulley, and you aren't squinting through two notches to line things up.

I have seen assertions that the pulley TDC can be off some. That it is best to establish a TDC mark on the flywheel, and use that. I tried that, but didn't see enough difference to continue on the engine in question.

A larger source of frustration can come from the pin. The pin is not what holds the cam timing in place. The partial teeth (early engines had a full circle with full holes back there, but that stopped at some point) are not strong enough for this. It is the friction between the parts imparted by the torque on the big nut (or small nut, in the later cams) which holds things where you set them. If this friction is not strong enough, the hardened pin can strip the inner teeth.

So it is the timing with the nut firmly set (not necessarily at final high torque, but well tightened so it won't change when you put the big torque wrench to it) which counts.

And the pin and its vernier system do not locate things precisely. You can get 0,020-0.030" (which will vary with cam slope) of difference within the same pin setting. You can prove this to yourself easily by inserting the pin, holding (as needed) the crank, and waggling the cam holder tool to and fro and watching the dial change. So getting spot on calls for getting the pin in a suitable hole, and also holding the reading while snugging and at least partially torquing the nut. I think getting exactly (based on the resolution of your dial indicator) the reading you are shooting for on both cams is a result of either luck or incredible patience.

One can take comfort from the fact that the factory gives a tolerance for the overlap setting.

Walt

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

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.

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.

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.

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.

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.:eek:

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.

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.

http://forums.pelicanparts.com/uploa...1268761320.jpg

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.

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.

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??

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

Youre with in the spec of .1
Bruce

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

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.

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