Hello Jaglovers, I am changing the old xk camshafts for the later better one’s, because of the noise they make. When I bought my XJ6 from the year 1975 long ago, remembering that the engine noise was better. Reading something about the oil line was direct from the oil filter and thought this was the solution, but reading here at Jaglovers forum, I fund out that it was also the the later camshafts from the year 1968, the series 2.
Thank you all.
While the cam profile was changed on the later camshafts, if you are having enough noise out of your engine to be that bad, check your cam followers for wear. I did the swap that you are talking about in my '69 engine that was making a lot of cam area noise, thinking it was the cam profiles that were the source. It was really the wear in the cam followers and their guides. Take the cams off and with your thumbs on the cam followers, try ‘rocking’ them side to side in all directions. There should NOT be any appreciable slop between the follower and guide.
As Kassaq said, check the wear between the follower and guide. You are using a later xj6 head and they are they are known to wear quicker. Also, a hold down kit should be installed.
Phil
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Just to clarify, I believe that the change in cam profile occurred a bit later in the Series 2 run ( e.g. my April 69 build has the earlier 004/006 cam).
Kassaq - did you change the followers and the guides or just live with the sound once you knew what it was?
Valve noise on these engines is FAR more likely due to worn tappets or guides than the cams. The later cams sound the same at idle, and have a different sound only at high RPM. Changing cams will almost certainly make little or no difference.
Regards,
Ray L.
Hard to tell from your photos but it looks like the cams you are using are the ones with .004 and .006 clearance - that is the earlier noisy ones. Agree that most noise comes from loose lifters in the bores, but the later parabolic cams 69 and on, were quieter.
Is there any downside to using the later cams; other than the trouble and cost of changing them?
The change-out will involve increasing the valve clearances from 0.004/0.006 to 0.012-0.014 (both intake and exhaust). If the parabolic cams have the same base circle dimension as the earlier cams (do they?), that means that replacement shims will need to be 6 to 10 thou thinner. It wouldn’t surprise me if that pushed you into the region of thinner than minimum spec shims in some cases, which though available, won’t be quite as easy to source. If, like me, you already have a couple of “thin” shims installed with the old cams, you may require new shims the thickness of rice paper for the new cams. Not good…
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Hi David I have a set of the parabolic cams here and measured them relative to stock cams, as I’m thinking about using them in this stroker motor I’ve built. Difficult to measure - I’m no machinist, but I concluded that the parabolic cams have had .008 removed from the base circle, so they will not require different shims from a stock cam. This also leads me to conclude that they won’t affect performance (which also appears to be a general consensus about them.).
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Thanks David and Terry. That’s where my question was leading; any change in performance.
Okay - the 004/006 cam will be noisier than the later cam and some modest wear in the tappets and guides is also a common source of noise. So…
Within reason, is there anything here to be concerned about? Valve clatter may be unbecoming in such a fine engine but does it really harm anything?
I should be used to it from my years with TR engines where, if you can’t hear the valve train, then you know they are too tight.
My 69 engine has has noticeable valve train noise at about 1500 rpm. It has new cam followers. But for 50 year old technology, I am more than satisfied !
Dennis 60 OTS
I wouldn’t worry about it George - most have some clatter.
I bought a rebuilt head from Coventry West (a SIII XJ6 head with the larger valves) and put it on my car. I am super satisfied with the head, and now have a quiet engine at idle. If I were you, I would get a rebuilt SIII XJ6 head and be done with it. Putting tappet hold-downs on the exhaust side is just common sense also.
I changed .004/ .006 cams to .010/ .012 and found virtually no change in shims needed. Maybe a little quieter
Good Information. That reinforces Terry’s post above.
Kassag I’m curious about how your car idles with the larger valves. Have you noticed that it’s a bit rougher? Typically the fuel injected Ser III XJ6’s (all have 1 7/8 intake valves) have a bit of a rough idle, that I’ve been told is normal.
I have dual SU HS8 carbs on the car, with Ray L’s EDIS ignition system. It idles nice and smooth. If I had ZS carbs and a marginal distributor, who knows what kind of idle I’d have regardless of the valve size or cams. The car is an absolute dream to drive. I have a 5-speed Medatronics/Tremec transmission with a 3.07 rear ratio. It is quiet on the road, and accelerates smoothly. With a manual transmission, it is difficult to tell how much more power the engine feels like I gained, as it depends on how much you press on the pedal and how high you want to rev before switching gears.
Hi there Kassaq, yes I have the bigger inlet valve’s, so it must be from a SIII XJ6 head that I bought here in Holland for not so much money. Cleaning the valve’s now and machine them in the sittings, having the old cams from a Mark2, wasn’t sure to use them. Reading from Jeff Smith that there are better one’s. So bought them and waiting to arrive.
always interesting to see others workbench… need any cassettes or are you more of a “short-wave” kinda guy? 