From: Marc Thomas [mmthomas@ix.netcom.com] Sent: Thursday, September 21, 2000 2:42 PM To: 928 Subject: [928] DEVEK Cam Timing.. The adjustment of the cams can be modified for slight changes in the hp and tq peaks...we would suggest that those who have automatics might be better served by advancing the timing by 2 - 5 degrees, thereby moving the tq peak....down by a few rpms Davids 928 cam timing was nailed - PERFECTLY! And the 928 showed its true nature..... It is all about detail.... -- Marc M. Thomas DEVEK 650-592-5287 phone 650-610-0557 fax http://www.devek.net From: Ken Postma [postmak@uswest.net] Sent: Thursday, October 19, 2000 11:42 PM To: 928 Subject: [928] Re: what do you think it is. Cam Timing Well, The good news and the bad news. Thanks to those that responded with suggestions!! My shark is running, and just fine. The bad news is I don't know what fixed it!!!! I was playing with various electrical connections and it just started! Well, after turning the key. The last thing I did I undid and my car still started. So that wasn't entirely it. The results of my cam timing. My right cams (cyl 1-4) were at 16 deg ATDC for the 1.6mm lift. My left cams (cyl 5--8) were right on at 20 ATDC for the 2.0mm lift. I changed the timing to 15 deg for both cams following the shop manuals, but setting them at 15 deg rather than 20 deg ATDC. So what did it do! The cam covers themselves are a PITA to remove and replace. The performance of the car does not seem to have increased for off the line acceleration. I do think the car seems more lively. Slight throttle application while in the 2000 to 3000 rpm range feels stronger. Downshifts feel stronger. Certainly, performance has not been hurt. 1/4 mile times have not been significantly affected. Without good timing, not a noticeable change, up or down. If I continue to think the car feels more lively, It was worth it. Ken Postma '86 928S (torque curve moved down some, I think) From: Marc Thomas [mmthomas@ix.netcom.com] Sent: Wednesday, June 27, 2001 1:30 PM To: 928 Subject: [928] Cam timing Advancing the cam timing on 4 valve 928 by 2-5 degrees will drop the torque peak back by about 100-200 rpms. It has a small effect on peak torque, but will reduce the peak hp since the torque curve is moved to a lower rpm range. This advancing of cam timing is not recommended for manuals or GTs and is most useful in automatics since those trans operate in the lower rpm range and a slight increase in lower end torque is useful. the process is simple..instead of setting timing at 20 degrees, set at 17 degrees for a 3 degree advance. Marc -- Marc M. Thomas DEVEK 650-592-5287 phone 650-610-0557 fax http://www.devek.net From: mlschmidt@sprintmail.com Sent: Tuesday, May 29, 2001 3:38 AM To: 928 Subject: [928] RE: Re Cambelt timing Question I just checked the cam timing on my car a few weeks ago. Checking and adjusting it isn't anything too mysterious or difficult to do. The hardest part is probably removing the passenger side valve cover. Before you start, the timing belt needs to be at the proper tension, and both valve covers need to be removed. To check the cam timing on the passenger side cylinder bank you need to turn the engine to top dead center on the compression stroke for cylinder number one. Mount a dial indicator to the cylinder head so that it will measure the amount of lift for an intake valve on cylinder number one. You'll need a bent tip on the dial indicator to be able to get it on top of the valve lifter, and the dial indicator must be mounted so that it measures perpendicular to the valve. If the dial indicator is at some angle to the valve stem you won't get an accurate measurement of the lift. Slowly turn the engine in the direction of normal rotation until the valve has opened the specified amount. On 1985 and 1986 model year cars the engine should be turned until the valve has opened 1.6 +/-.01 mm, and on the S4 cars the lift should be 1.8 +/-.01 mm. The value for the Club Sport and GT cars is 2.8 +/-0.1mm, and for the GTS it's 1.83 +/-0.1mm. If you turn the engine too far you'll need to go around two revolutions. You can not just back up until you get back to the specified valve lift. When you have turned the engine so that the specified valve lift has been reached, the pointer on the front of the engine should be pointing to the 20 degree mark. If it's not, you'll need to adjust the cam timing. To adjust the cam timing you have to remove the ignition rotor for that cylinder bank. Install and tighten three 5mm x 15mm bolts in the holes for the ignition rotor. This is to keep the cam sprocket from moving in relation to the cam until you want it to. Loosen the bolt on the front of the cam sprocket that holds the sprocket to the cam. You must counter hold that kind of oval shaped nut behind the bolt with a wrench when you loosen the front bolt. Check to make sure that the valve lift is still at the specified value. If it's not you'll need to rotate the engine until you get the proper valve lift again. Once the valve lift is at the correct value, loosen those three 5mm bolts you put in place of the ignition rotor. Turn the engine slowly in the required direction until the pointer on the center timing belt cover is at the 20 degree mark. The cam sprocket will move when you do this, but the cams should not. There is a woodruff key in the cam, and a wide slot for it in the cam sprocket. This will keep you from setting the cam timing too far from where it should be, but still allow enough movement for adjustment. When you have the engine at the 20 degree mark, tighten the three 5mm bolts to keep the sprocket from moving in relation to the cams. Counter hold the nut on the front of the sprocket and tighten the bolt on the front of the sprocket to 47 ft/lbs. Turn the engine two complete revolutions until the valve lift is again at the specified value, and check if the pointer is at the 20 degree mark. If it's not you'll need to repeat the procedure. Checking and adjusting the driver side cylinder bank is basically the same. On that side the valve lift is measured on an intake valve for cylinder number 6. The valve lift value used for checking this side is 2.0 +/-.01mm, and is the same for the 1985 and 1986 model years as it is for the S4. The value for the Club Sport and GT is 3.1 +/-0.1mm, and for the GTS it's 2.08 +/-0.1mm. The engine is turned so that cylinder number 6 is on it's compression stroke with all it's valves closed, and then slowly turned until the specified valve lift is reached. The pointer at the front of the engine should again be at the 20 degree mark when the valve is at this lift. Don't expect to get any massive power gains by adjusting the cam timing. The Porsche engineers did not miss a bunch of extra horsepower because of a slight change in the cam timing. What changing the cam timing will do is to move the power curve of the engine in the RPM range, not increase power. Advancing the cam timing will shift the power curve lower, and retarding it will shift the power curve higher. Advancing cam timing might give you a little better start off of the line because peak power occurs at a lower RPM, but then you'll have less power at the top end. Retarding it will have the opposite effect. In my case the driver side cam timing was okay, and the passenger side was off by about 3-4 degrees. A mechanic for a previous owner had been in there before, so I assume that's why the one side was off. Mike Schmidt '88 928S4 Black/Black "PORSCHE" cloth 928 Owners Club Charter Member PCA Chicago Region From: thom ross [tross2@nc.rr.com] Sent: Thursday, September 27, 2001 12:31 PM To: 928 Subject: [928] Re: How do I align camshafts at 45BTDC crankshaft- setting??? Hi Sharks: Thanks to everyone who has helped. Thanks to Wally Plumley for a response on the nightly download discussion list. He stated that I need to align cam gears at 22.5 degrees before the tdc notch on the cam gear to correspond to the 45 btdc crankshaft setting. My analysis of this is: 22.5 degrees before the cam notch corresponds to 3 teeth. The reason being: There are 48 teeth on the cam gear. 3/48 = .0625 = 22.5/360. BTW there are 24 teeth on the crank gear. Therefore, 2 to 1 ratio with the cam. This also means that you can align things 180 degrees wrong. At tdc crank, the cam bosses must point toward the exhaust hydraulic lifters. A further check is the rotors point left. -------------------- Thom Dark Blue 86.5 928 S3