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Camshaft and Crankshaft Timing

Camshaft and Crankshaft Timing

I have just recently rebuilt my engine 143k on previous. I have taken the liberty of replacing everything but the block and head casting. Here is the problem. After I assembled the motor it does not start. Keep in mind that I do this how I make my living. I thought it to be improbable that I messed up. My thoughts are that the cams have been placed in backwards and I have no way of telling wheter this is true. In all the factory manuals they show the number 6 lobe is facing the driver's side at a 45 degree angle, however mine are pointed the other direction towards the passenger side (exhaust side). Has any one ran into a similar problem ? PS when I say everything I mean everything Internal and external Fuel injection ect... - ImpExpServ

Looks like you bent some valves. Definately won't start. My condolences. - George Badger

Hello to all, Someone asked about the cam shafts and the possibility of their being backwards. This brought back vivid memories which I will put in the"for what it's worth" department. When I bought my 150 it had not been run for several years. After several hours of work I managed to get it started and it ran well except for overheating, not unlike Rob's tales of woe. I decided the head gasket was leaking and removed the head. The gasket was ok but the block need a careful flushing to get all the years worth of junk that had had settled in the cooling chambers. In any event I put the head back on and because I had moved the camshafts, they needed to be re-timed. I carefully read the manual and bought one of those metal tools which you put on the notch of the camshaft so it is aligned the correct way. Keep in mind that this was early in my learning curve for Jaguars. I was very careful and with the No.6 cylinder in top dead center, the notches on both the intake and exhaust camshaft were positioned exactly where they should be. I completed the rest of the engine hook up and got in to start it, expecting that I would soon be proud of my efforts. I can not begin to explain my horror when I heard this terrible metal clashing sound. I was dumbfounded. Again I checked everything and verified that the camshafts were properly set. Eventually I convinced myself that I must have been hearing things so I tried to start it again. Again there was this horrible noise coming from the engine. Remember, I had been able to get the engine to run before, so there must have been some mistake in my reassembly. I subscribe to the Zen school of automobile repair which holds that if you look at something long enough, the answer will come to you. It took several days of starring at the engine before I saw something that was not quite right. The lobes on both the intake and exhaust camshafts pointed the same direction, not withstanding my care in having the notches in their correct place. I finally removed the exhaust camshaft and guess what? It wasn't an exhaust camshaft at all but a intake camshaft. Of course it would not run, the intake and exhaust valves were opening at the same time and running into each other. For reasons at which I can not even speculate, the prior owner had removed the exhaust camshaft and replaced it with an intake camshaft. He had rotated this 180 degrees when it was installed and the engine ran.I learned from this that the two camshafts are mirror images of each other. The engine will run all day quite nicely with two intake camshafts or even two exhaust camshafts if they are positioned correctly. Just don't use the timing tool on the notches. You can time one the correct way and then position the other 180 degrees from the first. I finally got the engine running but later decided it would be better to remove the head and replace the valves that had been striking each other. I still wonder what possessed the prior owner to resort to using two intake camshafts. - Happy New Year to all, Don Sime, Xk-150 fhc

Don- I just have to ask this one, was the the flywheel also on 180 deg. out and did the windshield wipers run out of synch? There seems to be a lot of this strange "180 deg." stuff around. Will old Jags cease to run at all, come the Millenia? Drive while you still can! Happy New Year, regards, John Morgan

All else being equal, I'd suggest that you're timed 360 degrees out of phase (crank with camshaft). Try crossing the distributor wires (swap two at a time across the distributor). If you have compression during cranking, you probably are firing the plugs at the top of the exhaust stroke instead of the compression stroke. A proper solution woiuld be to remove the camshafts, rotate the crank one full turn, and refit the camshafts in the same location they were formerly in. If it runs with the plug wire swap, if it's not a Customer's car, leave it alone (but make a note where a subsequent owner can find it, and also to remind yourself later on). This is a common mistake, traceable to Jaguar's numbering the cylinders from the back of the engine towared the front, instead of the more common and sensible way -front to back! Take heart! I've done this, too!! Doesn't hurt the engine;only your pride. Hope this is it! Let me know! - Larry Schear, Twin Cam, Inc.

Someone asked a couple days ago about telling intake and exhaust cams apart. Haven't seen a reply yet so here goes. When you go through the usual setup with #1 (rear) cyl at TDC and cams aligned with notches perpendicular to the cam cover face, the #1 cylinder cam lobes should point toward each other. I thoought I'd heard this before but wanted to verify with real parts before piping up. This translates to picking up a cam from the bench - floor, parts bin, etc. :^) - with the drive gear end closest to you and the timing notch toward the ceiling, look at the farthest lobe, if it points right, its an intake cam, left, its exhaust. I was able to verify since the head for 670640 is almost completely stripped (one exhaust stud testing my patience). What is the best method to remove the rust deposits from insde the aluminum head? Any help you can give would be greatly appreciated. - Dave Gomes, XK120 OTS 670640

If you have any questions or comments send e-mail to: ted@jag-lovers.org
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