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Cylinder heads on 4.0 vs 4.2


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Hello Everyone.

New to the forum and i have questions regarding the cylinder heads. Is it the same cylinder heads on a
1999 S-type  4.0 V8 as it is on a 2003 S-type 4.2 V8? And if not, what will the difference be?

And if one engine uses VCT and one does not (as i understand the supercharged does not), will the
cylinder heads still be the same ?

Reason i ask is that i just bought a 4.0 l engine and plan to tune these cylinder heads and after work is done
put them on a 4.2l.

Thank you and all the best from Carl Johan

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Hi Carl

I'm not personally sure about whether or not they will fit but if you have both heads there it would be a case of taking measurements of all passageways, heights, valve lift, etc which will take time but at least you would be certain that nothing untoward would occur by swapping the heads.

Would be interested to know how you get on with this

Cheers,  Trevor

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Hi Trevor.

Thanks for your reply. I have not taken the cylinder heads of the 4.2 l since its a daily driver so
i can not compare them at the moment. Just wanted to be sure before i do the work.

I will post new info as soon as i know.

Best regards

Carl Johan

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Have a look at the workshop manual for a quick guide, the schematics will show you any major differences. Having said that, with one engine having VVT I doubt very much if you will find them comparable. The VVT uses a grooved cylinder that is actuated by oil pressure, which in turn is controlled by a solenoid. This thrusts toward the cam, altering it's timing. Each cam has to be aligned perfectly along with each cylinder bank if it is stripped.

If you are planning on porting heads I would not carry on with a 4.2 head hoping it will somehow mate with the 4 litre block. Try your luck with the 4.0 head, it will be plenty fast.

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