The 'E' Type Forum

Rebuilding spare series 1 3.8 engine which a has warped head with not enought metal to skim flat. Have acquired both S 'type AND XJ6 4.2 series 1 heads and would like to retain tacho generator driven from the end of inlet cam.

The S' type has had a tacho drive fitted BUT as it is not straight port cannot be used. Is there anything of use camshaft area but realise that as all camshafts are individually line bored perhaps not. Perhaps someone can enlighten me.

I know about blocking the end cooling holes on the face at the rear of the 4.2 head but what I do need is a step by step guide to fit the straight port 4.2 head to 3.8 block and keep tacho drive as car is still positive earth.

I am sure this has been done many times before so apologies for asking again ?

Both cylider heads should bolt onto a 3.8l block. The ooriginal 3.8l engine had the "non straight port head" so I don't know why you say you can't use it. You are aware that any extra holes need to be plugged on the 4.2l head (if it has any - depends on how old it is). The problem with the4.2l head comes from what intake manifold you intend to use, as the 4.2 head has greatly enlarged water ports into the manifold. If you are using a 3.8l manifold those additional ports need to be blocked.
Both heads should accept a tach drive. Again depending on age of the 4.2l head you may have to drill and tap holes on the tach drive facing to bolt it on, but it will fit. I've used a tach drive on Ser III XJ6 heads without a problem.
What cams are you going to use? Up to a certain point (?) Jaguar continued to drill and tap the 4.2l intake cam to accept the tach drive drive dog. You just need to get one and screw it on. The 3.8l intake cam should already have the drive dog on. The cams (3.8 and 4.2) are completely interchangeble, and as long as they are straight are usable. I don't understand why you need to line bore the head - it's the cylinder head that's line bored not the cams. As I said the cams are interchangeble.
All the heads have the half circle machined into them at the back for the tach drive. Later cam covers didn't. You just need to get a cover that is.
The tach drive actually generates AC current and is completly seperate from the cars electrical system. Twring for the tach is no more than two wires from each post on the drive to two posts on the back of the tach. As it's AC it dosn't matter which wire connects to which post (not polarity sensitive)

Just a thought, but have you considered swapping your S-type and 4.2 head for a rebuilt 3.8 MKX head from VSE?