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les_garten les_garten is offline
Macht Schnell
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Join Date: Jun 2003
Location: PSL, FL
Posts: 861
I hate it when it sits there and mocks me like that!!!


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!
---Les Garten---85 930, Andial IC, GHL Headers, Fabspeed Dual, K-27 HF2, 3.4 JE Full Finned 7.5:1 CR, 964 CAM'd, Carerra 3.2 Manifold Cut/Flipped, Tec3r, Siemans 55#, GSF Fuel Rails, Clewett Crank Trigger, Clewett Cam Trigger,Dual Plugged, ARP Head Studs/Rod Bolts, Clewett Wires.Tial 46mm WG, Tial 50mm BOV, WEVO Shifter,934 Boost Gauge, Wideband EGO Sensor/Gauge, C2T Head Gaskets, '88 MB 300TE,BMW R100RT

Last edited by les_garten; 07-04-2008 at 12:04 AM..
Old 07-03-2008, 11:56 PM
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