Head 0.0115“ tolerance - needs skimming or scrap?

the 4.2 engine thought as an interim engine for my 1970 E needs fixing up. The head is off, #5 valves stick/bent. With a machinist straight edge I measure the bottom as 0.115“ (correction thanks Paul! 0.0115“) too high in the middle area. It‘s lumping upward. Cam bearing seats show the same pattern, though only (roughly) 0.006“

Is this scrap, can be bent back, or sorts when torqued? Just skimming the bottom surely won‘t fix the cam bearing seats?

I really would like to use the engine for say 5000miles until I have my original engine fixed up. Them the interim engine goes back in the shelf.

Thanks for insight.


#5 cyl., yet uncleaned

Oh, and the engine #

There was a gentleman in the Jaguar Club of Houston who restored an XK 120 to a 100 point standard. The head was warped and he wanted to save it. He found a company who straightened it. Basically they bolted the head to a very heavy steel fixture and heated it in a furnace. I’ve no idea of the name of the company,l but it was written up in the Jaguar Journal, probably sometime between 1997 and 2000. Look for an issue featuring a red 120 with a tan or camel interior on the cover.

A couple of maybe useful links:


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Just suiting up into my fireproof overalls here.
If its an interim head then I would clean it up and bolt it on, the head bolts should pull that amount down and seal for sufficient time.

Classic Jaguar in Austin Texas straightens warped heads using a furnace. In the end I think it comes down to how much money you are willing to spend. Good luck.

At a tenth of an inch warp?

VERY short working life for the gasket…

Is it 115 thou or 11.5 thou?

11.5 thou, resp 0.3mm

If the warpage of the head surface is worse than the cam bearing milling, I would assume that it was milled already?
Now if you just skimmed it it would bend the camshafts and probably melt the bearings even more. If you wanted to bend it all back in shape we would have to reduce it to bare aluminium and put it in an oven. Maybe re-bore the cams, none of that is what we would do so if anything we’ll need to establish if the head is good as it is.
Per the link I sent you 1/16th (was it?) is okay but not good, but .3mm, I doubt that this will make that engine fail in the next few years. Even if, we might be able to change the gasket within a day, given our recent practice :slightly_smiling_face:

Paul, that should add up to roughly A hundreth of an inch, not a tenth! (Or am I mixed up!?!) 11.5 of 1000. I double checked today in mm, it‘s about 0.3mm.

It was posted as 0.115".

Paul, my bad. I made a mistake in that it should read 0.0115“. Now corrected above.

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Flat enough to reuse, with a composite gasket!

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Your main problem appears to be whether the cam bearings will be in line when the head is fitted, as the 11.5 thousandth can be skimmed off the head if required. That is providing the head is not on its facing limit AND the block deck has not been pulled upwards.(Not yet mentioned!!)

To check the cam bearing line bore I think you would be able to complete the following to check alignments if the engine is only going to run a short while.

Clean up the head and block faces and remove the valves. Buy a set of cam bearings; you are going to need these in any case. Refit the head to the block placing extra spacers under the head nuts to make up for a lack of the head gasket and torque to 50 lb.ft. You may need to position the crankshaft so that the pistons are off TDC to avoid a cylinder head foul.

Replace the camshafts, with the new shells but no camshaft buckets. If alignment is correct you should be able to turn the camshafts easily by hand, if a camshaft locks up you can at least slightly loosed the camshaft bearings to judge the fouling situation.

This type of checking is done on other twin camshaft engines other than Jaguar when the cam bearings are hand fitted.

Thanks for your replies. The block is flat, and overall seems to be clean and in good nick. I‘ll open the bottom soon enough and see whats in there.

You‘re right, cam bearings are being ordered anyway, I‘ll go the route to check cam alignment thanks for that tip.

I‘ve taken out some valves, #5 both slightly bent and on order as well. I‘ll check all.

Thanks for your input. I‘ll clean up and test assemble and be back. Assuming parts will arrive shortly.

I asked about this very many years ago,

there is a spec for this measurement

mine was less than yours, less than .005" as I recall

the unanimous verdict from experienced Jag engine guys at the time, was that was too much
(to re-fit without skimming)

I`ve got an appointment on wednesday with a local engine overhauler. He does the lot, so I´ll let him have a look. The head has not been skimmed before so enough material there for skimming I guess, my main concern as nwg stated is the cam alignment.

I agree with Robin. Unless you bent the head after you took it off, it was working fine for many years before you received it and took it off the engine. There’s no reason to assume it won’t work again when you bolt it back on.


that sounds encouraging, thank you. I tend to feel the same. But with good companies just around the corner it wouldn‘t be wise to forgo their opinion.

We loosened the acorn bolts, sprayed WD40 into the studs and let it sit for a time, maybe short weeks. The head came off beautifully, easy liftoff. So until then the head must have been straight since it was bolted to the (straight) block. I‘ll see what the guy says tomorrow.

Also this is my trial run for the future fixup of my original engine. So the learning curve is worth something.

A machinist’s straight edge with feeler gauges is ok but not the most accurate way to measure flatness. Machinist’s bars are better, but the best would be on a granite surface table.
Professional rebuilders will generally recommend to spend more of the customer’s money because they have to guarantee their work and don’t want to take a chance on anything.
My opinion is that .011" is probably within the ability of the original type gasket to seal. Mine was about .005" as I recall and it has been fine for 11,000 miles with a metal gasket.
Can you put the head on the block without a gasket, tighten it down and take more measurements?

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Also, sans valves and buckets, to see if the cams free up, or get tighter.