Cylinder head change

Technical advice Q&A

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Bernie2015
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Location: Devon
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#1 Cylinder head change

Post by Bernie2015 » Wed Nov 28, 2018 11:15 am

Im about to change the cylinder head om my 66 OTS from a head from another Jag to a correct period. When I say 'I' that means someone else that knows what they're doing.
I'm going to source the parts from SNG Barratt. Any advice out there from someone who has done this job before in terms of all of the parts to purchase and other jobs that may be worth doing while the head is off?
Bernie 1966 S1 OTS

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christopher storey
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#2 Re: Cylinder head change

Post by christopher storey » Wed Nov 28, 2018 11:42 am

Off the top of my head ( pun intended)

Top end gasket set
1 cam cover gasket for each side
2 Exhaust gaskets if not included in set
Inlet gaskets ditto
Copper washers for the rear cam oil feeds
Possibly, the JEC long bolts for the oil feeds
2 exhaust rings if not in set
? Brass exhaust nuts
Copper washers for cam cover acorns
Locking wire for sprocket bolts

As far as work to do on new head, how long is a piece of string ? Dependent on condition, valves and springs , possibly new cam buckets, set of cam bearings, ? guides and ? seats

As a matter of interest, what is your present head from, and what is wrong with it ?

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Bernie2015
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#3 Re: Cylinder head change

Post by Bernie2015 » Wed Nov 28, 2018 12:01 pm

The current head is from a 420 ie 7F prefix which is in perfect working order, it's just not right for the car.

I've got a 7E prefix head which is correct for the year, many thanks for the info.
Bernie 1966 S1 OTS

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Bernie2015
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#4 Re: Cylinder head change

Post by Bernie2015 » Wed Nov 28, 2018 1:32 pm

I've just looked in the knowledge base and although I can see a servivce manual for the 3.8L engine there doesn't appear to be one for the 4.2L. I presume compression ratios, tappet clearances, valve timing and clearances will be different for the 4.2L?
Bernie 1966 S1 OTS

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christopher storey
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#5 Re: Cylinder head change

Post by christopher storey » Wed Nov 28, 2018 4:07 pm

No, there is no difference in the timings/ compression / clearances etc until the parabolic cams arrived c 1968, when the only change was that the valve clearances were increased. The straight port heads ( except the S3 XJ6 which had larger valves ) are identical in every respect to those on the 3.8 litre cars . When the 4.2 arrived Jaguar changed the cylinder spacing but kept the heads the same, which is why on 4.2s there is an offset between some combustion chambers and the bore centrelines

The 7F head is functionally identical to any other straight port head, so all you will gain is to change one non-original head for another non-original head, albeit this time from an E type

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politeperson
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#6 Re: Cylinder head change

Post by politeperson » Wed Nov 28, 2018 7:30 pm

Buy a punch set.

You only need to change an F to an E.

Consider using the "i" on its side.

ha ha.
James

L.J.K. Setright was right.
"You just cant beat a good E-type"

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