Setting Cam Timing
 

Some of you guys probably don't go into the motor rebuild forum but you still may know how to do this. How the he!! do you set the cam timing on these motors? I have no "Z1" mark on my pulley. There is no mark on the cam sprocket anywhere. How do you know when the motor is at TDC? How do you know when #1 is TDC and then where do you set #4? I just got the longblock back together and went to set the cams. After an hour of staring at it like a complete idiot I figured I would share my stupidity with the board and hope that someone has a link to the rosetta stone of how to do this. Is there a video anywhere on the web that I can watch to see how someone would actually set the timing on a 1985 930 Porsche??? Ugh... and I thought the hard part was over. :confused:

You find TDC by removing the spark plugs and putting your thumb over the plug hole of the desired cylinder. While an assistant carefully rotates the motor by hand, feel with your thumb for compression. When you think the piston is near the top, put a srinking straw, pencil, length of rod, something into the spark plug hole that will not damage anything. When the rod indicator reaches its maximum extension, you have found TDC. Make sure the marker is always in contact with the piston.

I believe #4 cylinder should be 180 degrees offset from #1 cylinder. This means #4 is at BDC when #1 is at TDC. To get #4 at TDC, rotate the crankshaft 180 degrees.

Hi,
I'm confused here, the stock pulley has a TDC mark for adjusting valves for Cyl 1 and Cylinder 4. That's the mark you use. Do you have Wayne's rebuild book?

Les

I have both of Wayne's books and Bruce's book and a whole host of other crap that I am ready to throw in a burn barrel. I have not yet had the pleasure of adjusting the valves... didn't own it long enough before finding a broken headstud (July 2007). I figure I will adjust them now that the motor is out and laying on the floor mocking me...
http://forums.pelicanparts.com/uploa...1215148007.jpg

So you do not have any cams installed to adjust?

Interesting- pushrod->SOHC->4cam->no cam?;)

That was from earlier today. At this point it has 6 heads (maybe it is Medusa), two cams and a partridge in a peartree. I am going to give up and try again tomorrow. I sure hope my Z block and dial indicator get here soon from our host. I will try the drinking straw tomorrow to locate TDC and see if I can find the correct marks on the pulley. That should keep me busy till the forseeable future. Thanks for the humor Flieger... I needed that.

I hate it when it sits there and mocks me like that!!!

Anyhow...

Make sure you foloow the directions in Wayne's book for doing the initial roughing in of the cam timing. Make sure the right cam is in the right housing and the left cam is in the left housing.

Take a lot of time during all this procedure. First, you don't want to pull the motor and do this again soon do you? Nuff said there... Also, as Wayne says in his book, this is a difficult procedure, so don't expect to run thru this quick. Actually, this procedure is quite easy, and relatively foolproof. I hope when I'm done here you'll think so also.

The key to Porsche's procedure is understanding TDC overlap. If you get this concept everything else is easy as cake! Make a zerox of that TDC overlap graph in Bruce Anderson's Performance Book and really look at why Porsche is using that as a timing reference. If you can understand that Graph and what it is saying, you'll understand why more lift advances your cam and less lift retards your cam in reference to your TDC/Overlap Spec.

It seems like I'l rambling, but I'm going to press on and see if I can make a real mess of this!! I have an '85 like you, I've timed SC's on the Stock pulley and 964's on a Clewett Crank trigger on mine. By the time you get this far, you shoudl have figured out where your TDC mark is on your pulley for #1 Cylinder. Keep in mind it is one of three notches that are exactly 120 degrees apart. It is the one with the two or three other ignition timing notches close/next to it.

There are two TDC's for #1 Piston. TDC Compression Stroke(where you set Valve lash), and TDC Exhaust Stroke(which we will now call TDC overlap). This is important, you time the cam at TDC on the Exhaust stroke.

Ok, on with the concepts here. TDC compression neither valve is open, thats where you adjust valve lash at.

TDC Overlap is exactly 360 degrees more, and it is the only place where both valves are open. This is kinda an arbitrary point that Porsche decided to time all their cams at. They grind the cams to perform how they want. They know that you will have a certain amount of lift on the intake valve at TDC overlap. This way you can install any Porsche cam by knowing it's TDC overlap measurement. You don't need a degree wheel because you set the crank at TDC on the exhaust stroke and set the valve lift and it's MAGICALLY timed. GENIUS!!

You do the same thing on the number 4 cylinder with the same Z1 maker. You could also look at it like this. You set CAM time on #1 Cylinder when you are at TDC/Compression on the #4 Cylinder. You set CAM time on #4 Cylinder when you are at TDC/Compression on the #1 Cylinder. If this statement doesn't have you confused, I'm just gonna keep on ramblin' till I do!

The reason why this is done this way is all you need is a dial indicater and you can time these bayby's any way you want. NO DEGREE WHEEL REQUIRED! This is based on the assumption that TDC is accurate on your pulley. A smart move would be to "Correct" your pulley by determing true TDC and making a 'corrective" notch if it is necessary. If you're building for over 500 HP, this might help.

So if I made this ramble clear, let me add a little change to how Wayne explains it. He has you turn the crank till you get the lift on your Dial, loosen up the cam nut so the cam stays at that lift and turn the crank to Z1/TDC and then insert the index pin and lock the cam nut.

I had problems doing it that way, I found that the valve springs at that much lift with the very tight cam chain immediately wanted to start mving the cam as soon as you loosened the cam nut. So Now I'm not at TDC and the valve springs are trying to "push the cam away". We tried this for an hour or so and said screw that!

Here's how I do it, If I'm wrong in doing this hopefully someone will pipe in here! I run the Z!/TDC overlap mark right onto the Case SPLIT line and hold it there. I watch the Dial indicater while I am doing this. Turn the Crank VERY Slowly when you approach TDC/Overlap so you can watch the indicator. I then loosen the cam nut and dial in the lift I want. You pull the pin out of the cam tooth, you can use a small screwdriver to advance or retard the lift to get the number you want. You then look for the pin hole that matches as close as possible, there will be only one, just like the freakin' Highlander! Slam that PIN in and then work on torquing the CAM nut. This will be the biggest PAIN. Takes two people who folow direction well.

Ohh, and one of those two people has to know what they are doing! Or three people, or what ever, even 8 people, BUT ONE GUY IN THIS CROWD NEEDS TO UNDERSTAND WHAT TDC OVERLAP IS!!

The CAM nut needs to be torqued properly for sure! Rotate the engine around to TDC/Overlap (720 degrees) while watching your dial and see if you got it the first time. If you did, Hooray, you're a GawlDang Genius GUMP! Now chech it two more times. If you got the #1 done, do the same for #4.

Ohh, one other option, offer some brew to a local Pelicainte in your area who knows how to do this! PM me and i'll get ya a phone number if ya still have questions.

EDIT: Going to add one more line here. You have to have three things line up correctly to time your cams PERFECTLY.

1) PERFECT Valve Lash adjustment
2) TDC on the Exhaust stroke known to Porsche as TDC Overlap
3) The correct lift on the Intake valve when at TDC on the Exhaust Stroke(ALSO KNOWN AS TDC OVERLAP)

See how simple that was!!

First time I looked at how to time the CAMs, I had no idea what was going on here, don't feel stupid!

Chopsticks... they're not just for fried rice anymore. I used a chopstick to find TDC for #1. Found it and there are two marks on the pulley close to each other. Either could be TDC. I forgot to take a pic and will post on Monday. But, for the time being, I set the valve lash on number one to be sure that I was doing everything correctly. Wow, getting that feeler gauge in there is a complete biatch... even with the engine sitting on the floor. Exhaust was a little easier then intake.
I understand compression vs. overlap. Just need my Z-Block to show up and pick which TDC pulley mark is correct before I move forward. I think I understand it better now. Unfortunately there are no distinguishable marks anywhere on the cam sprockets or cam bolts that I can find. I guess the only way to do this is blind and by feel/measurement.
The theory of setting the cams makes sense, I just can't believe that Porsche does not have easy reference marks to make this a much easier process.
By the way, my valves were tight... is that normal? I had to back off the elephant about 1/8 of a turn to get the proper lash. I always thought they got loose between checks... hence the clackity clack that made you feel guilty so you would go in there and correct the lash. Is there any benefit to setting them tight? Psuedo advanced timing? I would think that too tight just keeps the valves from closing all the way when most needed. But then again, it would also make them open a tad earlier too? Is this an old builder trick or simpy valves that were out of adjustment?

You might find indicator watch better suited for finding TDC. Chopsticks/screwdrivers are just not precise enough.

If the valves are too tight, they will not seat well. They will leak combustion gasses, robbing power and efficiency. This will also melt and bend valves because the head is not seating and transferring the heat energy into the seat and cylinder head where the cooling is done.

If the valves are too loose, you will hear lots of noise and there will be wear on the upper end from the clacking and misalignment.

You could try to put a suitable washer onto the chopstick (maybe a piece of cutout cardboard) with a rubber band above and below or some glue or tape, whatever. When you think you found TDC, slide the washer down flush with the head and secure the washer. Now turn the motor about 10 degrees either direction and see if the washer moves away from the cylinder head at all.

You should be able to find the mark now.

Just trying to save you the expense of a special tool...:)

Stomski Racing makes a TDC finder. The reason for the TDC overlap procedure., makes it easy to put any cam you want and time it to your engine. Also, you know they've been working on that engine since the late 50's really. It has a lot of legacy behind it to drag along. Quiet valves are valves that are committing suicide. Most valves will get tighter as they "wear into the seat" and recess themselves into the seat. You should look at the tech articles for the "Backside Method" of valve adjustment, much easier than how you are adjusting your valves, and i feel much more accurate once you get the hang of it.

Does anyone know the firing order for the 930 off the top of their head? I can't find it on any of the stickers in the engine compartment??? After reading Wayne's book he says the firing order for the turbo is different then the N/A. FOr the life of me I can't figure out how we can use the same cams, but that doesn't matter right now. I want to get the right hand cam timed and then the world can start spinning again :)
I have #1 set open .07mm at TDC. I also can't find any info on total lift for the cams. I measured like 8.5xx MM at full lift but can't remember.

1-6-2-4-3-5 I believe that's how it goes. Should be on a sticker under the rear lid I thought. You never saw the 930 marks on the cams? Since this is your first Rodeo, I would take my time and check yourself multiple times. Sort of Measure 15 times and cut once kinda philosophy.

Since I never took the left side apart I have confidence that the cam is in the right spot. Unfortunately the three different books that I have (wayne's, bruce and the turbo factory manual) all have different information. The factory manual states that at TDC the intake valve shoudl be open .07mm and I am dead nuts on that. Now I am going to try to get #4 to have the same measurement.
I have measured #1 about 20 times just trying to wrap my head around it. Everytime I rotate the motor I get about a tablespoon full of oil out of the lower oil line... my garage floor loves me :)

Are you sure that isn't 0.70MM??

les,
Now I am at a loss... I am going to post a pic of the dial indicator at measurement. I am getting dumber by the crankshaft revolution (maybe too much brake cleaner). I think I am reading this thing right but since this is my first Rodeo it never hurts to have another set of eyes. Apparently none of our local PCA members have any interest in this :) Oil cooled stuff is just not quite as exciting as the water pumpers I guess. Warranty's must be nice :)

Okay, so here is a pic of #4 at TDC overlap. The more I look at the dial indicator the more I believe that it reads .07MM. Does that look correct?
Also, the factory manual states "Intake lift at TDC overlap with 0.1mm valve clearance is 0.65 to 0.80mm" Does this mean I need to crank it all the way to the "red 70" to get the proper timing? If so, that means the left side (the one I did not touch) is also off because it reads .07mm (or the exact same as what it on the indicator in picture for #4. I was trying to match the two. If this is the case would I have noticed a power increase or decrease???

http://forums.pelicanparts.com/uploa...1215484700.jpg

BTW, does anyone know the "correct" specs for a 1985 930? Like I said, Bruce, Wayne and the factory manual all disagree??? :confused:

Oh yeah, you have to read it in reverse since I set it up with preload. So the pic actually shows -8 ticks from zero as the valve is going into the head.

Each one of those marks are .01mm, so your indicator is reading .08mm

Les is correct with:

http://forums.pelicanparts.com/uploa...1215524550.jpg