Camshaft lifetime

Technical advice Q&A

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Sirjames
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Joined: Thu Mar 15, 2018 10:41 pm
Great Britain

#1 Camshaft lifetime

Post by Sirjames » Thu Mar 15, 2018 10:54 pm

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.
James 67 OTS, 73 OTS 6.0L, and other makes

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jag68
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Location: Victoria BC Canada
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#2 Re: Camshaft lifetime

Post by jag68 » Wed Mar 21, 2018 7:57 pm

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
1967 E Type coupe
1968 E Type OTS
2007 XKR

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Gfhug
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#3 Re: Camshaft lifetime

Post by Gfhug » Thu Mar 22, 2018 9:29 am

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
S2 FHC Light Blue

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christopher storey
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#4 Re: Camshaft lifetime

Post by christopher storey » Thu Mar 22, 2018 7:41 pm

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

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kingzetts
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#5 Re: Camshaft lifetime

Post by kingzetts » Thu Mar 22, 2018 8:37 pm

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.
John '62 S1 OTS

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jag68
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#6 Re: Camshaft lifetime

Post by jag68 » Fri Mar 23, 2018 12:28 am

Does the SNG part have a number?
1967 E Type coupe
1968 E Type OTS
2007 XKR

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kingzetts
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#7 Re: Camshaft lifetime

Post by kingzetts » Fri Mar 23, 2018 9:05 am

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.
John '62 S1 OTS

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Topic author
Sirjames
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#8 Re: Camshaft lifetime

Post by Sirjames » Mon Apr 02, 2018 5:03 pm

Thanks guys for your advices, I'll keep investigating and let you know what happens.
James 67 OTS, 73 OTS 6.0L, and other makes

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Series1 Stu
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#9 Re: Camshaft lifetime

Post by Series1 Stu » Mon Apr 02, 2018 8:58 pm

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
Stuart

If you can't make it work, make it complicated!

'62 FHC - Work In (slow) Progress
'69 Daimler 420 Sovereign
'94 X300 XJR basket case

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