'38 Rocker Shaft Posts and Arms

My rocker shaft posts are numbered 1 to 6 with #1 at the front. It is the fixed post with the set screw in it to hold the shaft. The book says it should be at the rear. The other 5 posts slide freely on the shaft. Should I change it?


My rockers arms have numbers 46138 & 46139, six of each, but seem to be not in matched pairs.
I measure the center to center spacing of pairs of valves at 1-5/8", and of pairs of pushrod holes at 1-1/2".
So I think pairs of rocker arms should angle towards each other on the pushrod side, and away from each other on the valve side.
Is this right?

It is also missing the large flat washer between the oil feed tube banjo and the flat wound spring on the end of the rocker shaft.
Looks like somebody put this rocker shaft together wrong.

Hi Rob.
My engine is later L1905 and has different rockers to yours but I do presently have it out of the car if there is anything I can tell you about it that would help.
I hope to be reinstalling it later this week.
Cheers, Graham.

These any help Rob?
Peter B

Hi Rob,

I think you have the rocker shaft pretty much sus’ed. I think you should have your retaining screw on the rear post although this is possibly less critical than if it had been a MK4 where the oil feed is through the rear post.


However the comment about the posts sliding freely on the shaft may be a concern. On earlier cars the shaft was a press in fit . The hammering upwards in operation could loosen what started out as a tight fit and the shaft would move in the post. One could remove the rocker cover and with the engine running put a. Finger on the post and feel the tapping.
Later jaguar put a slot half way across the post on the side the stub went through so that tightening the mounting bolts actually clamped the post to the shaft.
Something that is easy to retrofit with a hacksaw.
The copper feed pipe that provided oil to the shaft was a bit prone to fracturing , hence the change to oil feed through the post. Certainly worth inspecting and personally i replace the copper with a longer piece with an extra loop.
Although thinking about it , this fracturing could have been a result of the early posts allowing the post to vibrate in relation to the head.

Thanks to all of you for your responses.
My engine number is L205.
I decided to switch the fixed post to the rear, although there didn’t seem to be any real reason other than the numbers on them. Now #1 is at the rear. Being around Jaguars for 50 years I’m used to that. :grin:
I am familiar with the oil feed passage on the rear post since my Mark V has it. Took the opportunity to clean the inside of the shaft although it wasn’t very gunky.
The other posts have the slot as mentioned by Ed; it is about 1/64" wide, though they may have been wider when new.
I fitted a 46138 on the forward side of the fixed post and a 46139 on the rearward side and measured them. 1-1/2" on the pushrod side and 1-5/8" on the valve side. So that must be right.
I put them all on, the 46138s forward of each post and the 46139s rearward. Looks right.

Adjusted all the clearances at .012" according to the label on the rocker cover. Replaced the missing washer on the banjo end with one from a Mark V. A loop on that tube would make sense, will work on that. Runs pretty quiet and smooth now. Good oil flow too. Used my stethoscope to listen at each post, #4 was noisier, readjusted those, now all making about the same amount of noise.


Someone may have replaced the posts or some of the rocker gear. They didn’t slot the posts till well after the war. from my experience
Referring to my Bradshaw’s Handbook as Michael Portilo would say . we see that he posts were changed from engine M1101 but I can’t comment on Mk V as i have nothing so modern as that .

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Can I ask what spark plugs you use and your gap setting.
Regards, Graham.

Could be I suppose. Somebody certainly mixed the rocker arms around.
I’m not familiar with Bradshaw or Portilo, although we have an excellent restaurant chain here called Portillo’s that does a great Chicago style Italian beef sandwich, but consulting my Lyons/Daffern/Whittaker/Heynes, the loose post bracket 43575 C.424 was used in all L M P and S engines. The part numbers changed from Batch 1 to Batch 2 in the '36-'37 book and do not have the C numbers. Perhaps they began slotting them without changing the part number, or added the C.424 when they began the slotting?

BTW all six of mine have the number 43574 on them, so they used the same casting for fixed and loose posts. The fixed post has a locking screw so no slot needed there.

Later engines have fixed post C.507 48560 with the larger base and oil passage.

On Mark V with H T and Z engines, the part numbers changed to C.2542 & C.2543 and the slotting method is different, not cut all the way through, though they retain the old numbers on the castings. No locking screw in the rear post either.

I use Champion L90C plugs with .025" gap.

Robert My goodness. You must immediately acquaint yourself with Michael Portilo’s {MP] Great British Railway Journeys. Not only to learn about the old Dart But how an English gentleman traveling must dress
From memory Peter Scott is a dedicated follower of fashion , and Bryan from the Pub list is oft mistaken for Michael MP.

Well I don’t think I could match Portfolio for sartorial elegance but I was on a train yesterday.


That’s the Durango and Silverton, isn’t it? Beautiful country!

I can only afford the economy seating.

Actually I did drive a train for a couple of summers at Adventureland.
Here I am in 1972.

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That’s the one! Very enjoyable. I spent most of trip with my head out the window and at the end of line my hair had turned from white to black.
Silverton was good too. We had lunch at the Lone Spur Inn that has a fabulous bar and a very good pianist playing Scott Joplin ragtime.

I do love Buster Keaton too


…s’why I hang my hat here!

The Antonito to Chama narrow gauge is also awesome!

Nice video! Interesting to see the double headed operation. I don’t know much about steam locomotives but they don’t appear to share the load very equally at times.


Not quite as accomplished as the C&T video but if you are able to tolerate 30 minutes of phone camera video then here is the joint effort of Mr & Mrs Portillo Scott covering our journey from Durango to Silverton.


Cool ride, thanks Peter.
Here’s another version, a western called Ticket to Tomahawk made in 1950 but set in the 1870s. Watch for bit players Marilyn in a yellow dress, and Jack Elam before he gets plugged, but don’t take the story too seriously. :wink:

Excellent! Thanks for that Rob. Best western I’ve seen since Blazing Saddles. Seriously though, very interesting to see the line and Silverton back in 1950 and good fun too.


I feel a bit guilty in maintaining this OT diversion but for those at all curious about life in the mines of places like Silverton there is a fascinating and scary account running on another forum that I subscribe to.


I gotta do that run, soon!!!