Removing the distributor MkIV 3.5

My distributor is supposed to have the mechanical advance and after the previous discussion on vacuum advance systems and knowing how many other things in this car were fixed, I suspect it either doesn’t exist or has seized up as the tests according to the workshop manual didn’t show any free movement.
So currently the engine runs well at low revs but when on road, can only attain a top speed of about 45-50 mph / 3000 rpm with engine completely out of power. Have checked fuel lines, float chambers etc and pretty sure has enough fuel at 3000 rpm so am about to tackle removing the distributor- any tips / advice for not destroying anything?

It does sound a bit like your centrifugal advance is seized. Strictly speaking you don’t actually need to remove the distributor from the engine to dismantle it but if you do want to remove it you can either just slacken the clamp bolt at the bottom or remove the single bolt that retains the clamp plate.

To access the centrifugal weights and springs you just need to undo the two peripheral screws that hold the contact breaker plate in the body. I think you need to unscrew the slotted screw in the top of the shaft that you will see after pulling off the rotor arm in order to take the centrifugal mechanism apart. You might find it easier to undo this screw whilst the distributor is still in the engine as the shaft will be prevented from turning.




Before attempting removal, you would be wise to turn the engine to a well-known position, like No 1 piston at TDC firing.

Although you may have no plans to turn the engine with the distributer removed it is surprising how the best plans do not always work out.

Looking ahead it may be that you decide to renew the main bushings in the distributer body. If you do so, then beware, many of the distributers have the main bushes cast into the distributer body. In those cases, any attempt to drive out the bushes will smash the body beyond repair.


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Even if you do set the engine to No 1 TDC on the firing stroke be aware that the distributor doesn’t have the offset spade drive that lets you pull the distributor out without rotating it. It just has the meshing skew gear at the bottom of its shaft so you will need to rotate it as you remove and replace it.


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Please be aware there is also a small setscrew in the front of the distributor adapter that locates in a circular groove in the distributor body. This setscrew has to be slackened back sufficiently (or preferably removed) to allow the distributor to be removed.

Thanks everyone- in end went through the top without removing and the weights etc all good, move easily so not causing the issue about lack of power when revs up🤔

Does it misfire above 3000 rpm? (stutter)
Check your static ignition timing.
Check your tappet clearances.
Test your compressions.


Doesn’t stutter- engine sounds smooth, revs well with power at low revs and pulls well about town speeds but then when try open road just runs out and 45-50 mph (2500-2800 rpm) is maximum, no reserve
Fuel pumps good, carburettors been serviced with new gaskets, seals etc, issues with fuel tank residues been sorted, 98 in the tank but is unleaded?
Going to check valves as suggested, play with timing if those all okay
Don’t have facilities for pressure testing- would need to go to motor mechanic

Ok so got mechanic to look…

Turns out missing cylinders 4 and 6 - one with broken push rod on inlet valve, the other might be lead related
Compression tests fairly uniform at slightly above or below 5 psi (although apparently it should be closer to 9.5?)
Advice on push rod replacement and where to source? Might as well replace all if they look the same as the fractured one - heavily pitted steel
Engine number S394 if that helps!!

Try Worcster Classic Spares Worcester Classic Spares - Classic Jaguar Parts Supplier
Or Davenport Cars Home - Davenport Cars

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My SL2199 had one pushrod slightly out of true.

I don’t know if anyone sells high quality replacements, perhaps they do.

Quite a surprise if inlet in cyl 4 was not opening at all, one would think it would affect running and the sound a bit more.

I once had a rocker loose and did notice, it sounded terrible! Fixed in 5-10 minutes. :slight_smile:



Maybe you are confusing the units?

5 bars or ATM?

That would be a bit low.

I measured mine, but I have 83mm STD XK 8:1 comoression ratio domed pistons in my freshly rebuit (a looooong thread in thus forum) MKIV engine SL2199 in my MKV DHC. I had a nearly catastrophic oil pump shaft failure (it jumped) so I wanted to check and measure everything, this is what I got (on an almost warm engine):

I did a compression test:

6: 10.0 bars / 145psi
5: 9.9 bars / 143psi
4: 9.9 bars / 144psi
3: 10.0 bars / 145psi
2: 9.9 bars / 144psi
1: 10.0 bars / 145psi


Could you post a picture of the fractured pushrod? There is more than one design in use.

Can you comment further on the compression test results? If you mean 5 psi, is this the variation among the readings across all six cylinders? And if you meant bar rather than psi, Pekka’s comments may guide you as well Perhaps there is a bit more to sort here. For example, if the intake pushrod on one cylinder was fractured to the point of not opening the intake valve at all, then compression test on that cylinder would be substantially different from the other five since air could only enter or leave via the exhaust valve opening.

Thanks- Worcester spares on speed dial already but only used in stock…

Richard Carter

Thanks Pekka- you correct- 5 bars not psi- all fairly similar readings but was done on engine cooling and mechanic said main point was to see if anything catastrophic so oil test not done but if going to pull things apart, might be good time to renew other bits
Photo of rod as removed
294mm long, 9 mm diameter (11/32’’). Think it may have been welded at fracture line. Holes each end in centre

Richard Carter

The oil feed is from the rocker but the push rod doesn’t need to have a passageway from top to bottom. The oil flows down the outside.


Thanks for posting photo. The pushrod shows a bit of pitting, looks straight, and maybe has some welding at the break point (but hard to say from photo).

Used pushrods can work fine. Given you are in Lincolnshire, getting a used one from Worcester or Davenport or querying Alan Gibbins may be easy path for your supply. Send me a note if used supply proves hard to find.

Chances are decent, subject to inspection, that the broken pushrod merely bounced up and down without causing much damage to tappet or rocker cover. Check as well to see if small fracture bits may be missing from pushrod. I’ve seen a rocker break with no collateral damage.

I’m back, after being off line for a week dealing with computer problems.

Pushrods are a tube with machined end parts welded to them. It looks like yours broke at or adjacent to the weld. If all else fails you could have it welded together again. Tricky job, might have to machine off the old weld, not for a beginner, best left to a pro.

Thanks Rob- yes it is a failed weld.
Have checked the others and all fairly pitted and quite lot of rust in oil, rockers, top gallery. Going to take head off and see condition and if anything else failed (well mechanic is…)
At the end of day, I really don’t know if this was a car in use or standing for a number of years. Quite lot condensation under rocker cover but oil colour ok.

Worcester spares got back to me- apparently this is a pushrod for a mkV engine- thought the engines were same? Difference? Is it important to get mkIV pushrods?

Richard Carter


The 3 1/2 Litres are essentially the same, but like Roger was pointing out, there are slightly different design if pushrods, at least two or three and I think two different lengths as well as some tappets were taller. So better to check and measure.

Also the pushrods on my MKIV engine #SL2199 in my MKV have the oil hole at both ends. Oil would be flowing (slowly) down from the rockers.