The 'E' Type Forum

Hi everyone,

I'm building a 4.2l long studs, big valves for a 1967 E-type.
So I'm basically replacing the engine by a more modern one.
My problem is that I have to keep the old camshafts for the tacho drive. I'd like to be sure they're still usable.
Is there a tolerance chart to measure them and see if they're usable or not?

Thanks in advance for your help.
J.

J The intake cam on the big valve head (BVH) can be used to drive the tach - it needs to be threaded to fit the screw on drive. However ......most BVH won't accept a generator because at some stage Jaguar changed the basic layout of the rear intake side cam bearing cap and it is not compatible. The original cap had a cowl that extended rearward and permitted the nose of the generator to fit inside it to mate to the camshaft, and also permitted a seal against the cam cover. Look at your old head and you'll see what I mean. I don't know exactly when this change was made but it has certainly been on every BVH I've seen. If the intake cam cover on your BVH is flat across the bottom rear then you have the non compatible cap. You are much better off to get the tach modified to work off the points. Mike Eck in N.A. does it.

Terry Sturgeon

If you're fitting big valves will they need the later cams with the 12-14 thou tappet clearance rather than the early 4/6 thou cams?

Geoff

Geoff - you can use either cam with earlier or later heads. The tappet clearance alteration is specific to the parabolic cams rather than related to the heads to which they were fitted .... but of course you are correct that when new, the big valve heads would have had parabolic cams in any case, as by the time the big valves were introduced parabolics had been standard fit for some 10 or 12 years or so

It is actually simple to adapt later heads with the short rear inlet cam bearing cap to accept a tach generator. You just need a half-cylinder of aluminium to fit between the tach generator and the cam cover. SNGB will sell you one. I have a later short cap head on my 3.8 with tach generator and this works fine.

Does the SNG part have a number?

Probably, but I’m afraid I don’t know what it is. Ring them and ask - if the sales staff don’t know ask them to check with Peter Stant.

Thanks guys for your advices, I'll keep investigating and let you know what happens.

To answer the original question. Check the camshaft by measuring the overall lift to ensure it is within the tolerances in the manual. Also check for scuffing of the contact faces. A little marking up is to be expected but if the nitriding is worn through then it's scrap.

The camshafts can last indefinitely if the engine is maintained properly. Regular oil and filter changes is the cheapest and most effective way of looking after an engine.

Regards