Cam timing check - post rebuild?
08-31-2006, 11:45 AM
#1
Drifting
Thread Starter
Cam timing check - post rebuild?
So as not to hi-jack Tripsters thread about his glowing header problem, I thought I'd ask the question in a new thread. To the expert 911 engine builders: is it adviseable to check the cam timing once a newly rebuilt engine has some mileage on it? You know, maybe after the chain, tensioners, and cams have some hours on them, is it advisable to see if the timing is still to spec? This quote from DonE made me think of the question:
Originally Posted by DonE
My engine developed an oil leak about a week ago - right at the cam gasket to cam chain box. So, I decided to fix it Monday and thought I would have to at least partially drop the motor. The good news, is that you do not need to drop the motor in anyway to adjust cam timing or repair a failed gasket. The bad news was that when I double checked the cam timing, it was .35mm retarded from target (or what I thought I set it at on the rebuild). So, I replaced the crushed paper gasket (crushed at one of the three bolt holes), reassembled everything and timed the cams at 2.35mm (range is 2.2 to 2.4). I put it all together and remembered that I did not torque the cam bolts.... WTF
So, after torquing the bolts correctly, I took the car out for a drive. I can honestly say (and some of you know my pet peeve of "seat of the pants measurements"), this motor rocks. The off boost accel is easily equal to a naturally aspirated motor. I took it out today and drove in city traffic - wow, what a difference. Its fun to drive in traffic now. It's hard to believe that .35 made this much difference.
I still have about an 8.5 on the grin-o-meter five hours later....
Tripster - good luck
So, after torquing the bolts correctly, I took the car out for a drive. I can honestly say (and some of you know my pet peeve of "seat of the pants measurements"), this motor rocks. The off boost accel is easily equal to a naturally aspirated motor. I took it out today and drove in city traffic - wow, what a difference. Its fun to drive in traffic now. It's hard to believe that .35 made this much difference.
I still have about an 8.5 on the grin-o-meter five hours later....
Tripster - good luck
Last edited by sand_man; 08-31-2006 at 02:59 PM.
08-31-2006, 11:47 AM
#2
Drifting
Thread Starter
In addition, just how hard is it to fit the dial gauge with the engine in the car? What about having all of the rockers in place...would this work against you as you try to make the delicate pin adjustments and sprocket movements? I have SC cams.
08-31-2006, 03:17 PM
#4
Instructor
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Don, Did you leave the chain tensioners intacked along with the sprockets and chain and just pull the bolt, washer and pin? Also, how much time and tries did it take with having to move the crank instead of the Cams? Did you just rock back and forth on the Z1?
08-31-2006, 06:37 PM
#5
Burning Brakes
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It was pretty easy - it just took time. The dial indicator can be installed with the upper valve covers off, on the #1 and #4 intake cylinders. My cams were very easy to adjust with all the rockers in place using the special cam tool. The adjustment took about 5 min each side with the most amount of time coming from pulling the motor through 720 degrees of motion. The cam chain tensioners were left in place.