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MG TD TF 1500 - Anyone have a Lucas 40048AF distributor

The Lucas catalog lists the 40048AF distributor as being fitted to the 1946 to 1949 MG TC. I'd like to know the measurement from the bottom of the housing (where the housing sits on top of the clamp) to the centerline of the drive gear. If anyone has this distributor and would provide that measurement I would certainly appreciate it. I'm on a mission to prove myself right or wrong. Based on my past detective work I pretty much know where this is going :-)

Tim
Timothy Burchfield

I cannot remember how I obtained the 40048 distributor in the attached photo, and as it only has one clip I do not know if I have ever used it. It is also rather worn, as there is 1mm of up and down play in the shaft.
However, pushing the shaft down, which is where it would be in operation as a result of the rotation of the camshaft gear, I have measured as follows. From the bottom machined face of the cast body to top of the gear = 57mm, and to the bottom of the gear = 69mm.
As the wear on the gear is to the top, it is obvious that it has been fitted too far into the hole in the block. Because the distributor was used with the micro-adjust clamp, my guess is that someone fitted it using the later clamp without micro-adjust, which was thinner.



R WILSON

Ray, thanks very much. I was beginning think the 40048 was a figment of my imagination. The measurements you supplied match up with a 40162 distributor that replaced the 40048. So the difference must lie elsewhere. The Lucas parts catalog has the same parts numbers for the internal parts of both distributors. But it does say the driving gear was supplied by the manufacturer.

Regards

Tim
Timothy Burchfield

It would be very helpful if someone could provide the same dimensions from a 40162 distributor, which I do not have - I am wondering if they are 3mm (or 1/8") less.
R WILSON

To the best of my knowledge, all DKY4A bodies are the same, and only the advance curves were different. The 40162 and 40048 are the same height and were both used on TC. The 40162 continued into TD production, and since the TD did not use the micro-adjuster, a 1/8" spacer was required to make up the height difference.
Steve Simmons

Steve, whee did you obtain the information that the 1/8" space was required on the 40162? I have searched high and low for that information from Lucas or MG with no success. Is that an owner decision or did Lucas or MG advise to install the spacer?

Thanks

Tim
Timothy Burchfield

Ray, as I mentioned in my first response to you the measurements for the 40612 distributor I have are the same as your 40048. I thought there might be a 3 mm difference a well.

Tim
Timothy Burchfield

Sorry, I misinterpreted what you wrote. However, Steve has supplied the necessary information, the 3mm being the difference between the clamp with and without the micro-adjust - thanks for that. I agree that the TD parts list does not mention a spacer, but I wonder if the 'securing plate', part number 67257, included the spacer. This securing plate became part number 17H5502 at chassis 24489, but strangely this was after the parts list shows a cotter bolt, 163405, being introduced at chassis 20942. I think the parts list sometimes confuses chassis and engine numbers, which I will investigate.
R WILSON

It's just general knowledge. I've never tried to find documentation because I never found a reason to question it. The helical gears have to mesh properly, and if you change the reach of the distributor then they no longer will. So by removing the 1/4" thick micro-adjuster and installing a 1/8" thick clamp instead, a correction had to be made. The factory would have to do this to make it work.

I see no reason why Lucas would offer a spacer since you could just order a distributor with the correct reach, but stranger things have happened. I suppose if one cared enough, a search through 1940s-50s Lucas parts lists might confirm one way or another.

It was also pointed out on another list that there may be variants of the DKY4A used on other cars. I have no knowledge of those, just the ones used on XPAG.
Steve Simmons

I have just remembered that there is a photo of a 40162 distributor in a thread in these TD-TF pages, so I have attached the photo. It has the 3mm spacer, so perhaps the spacer came with the distributor. I have another Lucas parts list for the 40162 distributor, and it mentions a thrust washer, which could be the spacer, but the washer is not given an individual part number.


R WILSON

Ray, If the part number is not given then that part did not come with that distributor. If you look along the line you will see part numbers for that washer for other distributors. As I mentioned, The Lucas parts catalog states that for the 40048 and the 40162 the distributor gear was supplied by the car manufacture. Perhaps MG fitted a different gear to the 40162 than that fitted to the 40048. All three of my distributor drive gears have an L stamped on them.

I am coming to the conclusion that neither MG nor Lucas was concerned about the distributor gear in the TD moving down 1/8". There is no listing in the MG service parts catalog or the Lucas Master Parts catalog for a spacer. There is no mention or pictorial representation in any of the three MG shop manuals I have, that show or mention a spacer. If the result of the driven gear moving down an eighth of an inch were detrimental to the cam or distributor why weren't people told to ensure a spacer was installed? It appears that the advice to install a spacer was an owner suggestion and not from the manufacturer or parts supplier. But I'd be appreciative if someone has information to change my opinion they would post it. Facts trump opinion every time.

Tim
Timothy Burchfield

I have some Lucas parts catalogues, but obviously not the one you have. However, the list of internal parts for the 40162 distributor specifies one thrust washer, even though no part number is given. The list of internal parts is the same as used for several distributors, but when a part is not actually fitted in a particular distributor, then there is a - (a dash).
I thought this proved something, but my lists show that an un-numbered thrust washer is also fitted to the 40048* distributor, but as my 40048 distributor does not have a spacer ring, the thrust washer must be something different. I accept that a 1/8" movement may not be much, but why does the 40162 distributor have a spacer fitted. I have several other distributors, so tomorrow I will check what they are fitted with.
I think the securing plate I mentioned before is just the distributor top plate.
* and the 40058, 40089, 40115, 40162, 40348, 40367, 40368, 40369 & 40441 distributors.
R WILSON


Tim, I have 4ea. 40162 distributers(all with spacers) and 3 of the gears have a "F" stamped on the gear. The 4th one has no visible marking. Don't know if this is of any value to your research, but I wonder why your are all marked with a "L".
Richard Cameron

Tim. I sent you a separate email. My TD has Distributor DKY4A 40048D Dated 9/48. I am reasonably sure it is not original for my 11/50 TD. It does have a 0.125" spacer above the holding bracket.

Again, can't say the spacer is original, but it has not had any issues running my engine.

A note to Jeff Schlemmer at Advance Distributors may give more information.

PS. If anyone has a TD distributor with a date of 1950 they want to trade or sell, I am looking for one.


Bruce Cunha

I would be careful to dismiss the necessity of aligning the helical gears, especially on the simple fact that you can't find a part number for the spacer. The thrust washer is not the same thing as the spacer in question, and despite the lack of a part number, the thrust washer is absolutely necessary. It seems incredibly unlikely that every distributor of this type unever installed on a TD has a spacer because an owner or mechanic somewhere decided it was a good idea. Rather than seeking proof that these thousands of spacers were installed for a reason, it makes more sense to seek proof that they weren't before removing them. You won't find that reason though. I've never giving it any thought because I've never seen a TC or TD without 1/4" of spacing between the block and the distributor. And the reason for that, the alining the drive gears, is a very good reason for it being there.
Steve Simmons

Tim. I did not read all the responses but any early distributor ( that not requiring a cotter bolt ) requires the spacer to compensate for the distance that would be lost without either the micro adjuster as used in the TC or the ultra rare manual cockpit spark advance that was used on some of the TD/competition models. The distributor view that Bruce provided shows the spacer. The other distance piece being the the actual external distributor clamp that bolts to the early engine block castings. If you have a cotter bolt block the spacer is not used.
W A Chasser

While reading through this thread and investigating the question, I made an interesting discovery, here it is.
The distributors which were designed to take the micro adjuster have a smaller second circular groove about an 1/8" from the top of the shaft. It is easy to understand why this groove is needed, without it the adjuster may/will jam up. So now the rule of thumb is, if you have this second groove on your unit, you need a spacer, otherwise, you don't.
About the micro adjuster, it was never fitted to TDs because, on LHD cars the steering column would interfere with it. No LHD TCs were made.

John

J Scragg

In my spares box I have a 40058 distributor – this was used, with clamp plate fixing, in the YB for a short period before cotter bolt fixing was introduced. It does not have a spacer, but I may have lost it as I don’t have the clamp either. Also, it does not have the groove mentioned above, but my 40048 distributor does have the groove.
I also have a 40358 (NOT the TD 40368) and a 40441 distributor, and neither have spacers. As they both have shorter stems, the previous dimensions being 51mm & 63mm, then it is apparent they used cotter bolt fixing.
R WILSON

Bill, the TC was equipped with dist 40048 from 1946 until 1949. The TC had the micro adjuster installed and a clamp . One would expect to use a spacer if the micro adjuster was removed. The 40162 distributor was fitted to the TD in 1950, coincidentally when the micro adjuster was dropped. You would think that if a spacer was required with the introduction of the 40162 Lucas or MG would have included it in their parts catalogs or workshop manuals. They did not. So either the 40162 distributor was changed to account for the lack of a micro adjuster or Lucas and MG did not think the driven gear moving down 1/8" was a big deal.

Regards

Tim



Timothy Burchfield

Steve, regarding the thrust washer: The manufacturer provided the distributor gear for the 40162 not Lucas. It was not a Lucas part. Therefore it makes sense that MG would provide the thrust washer since Lucas would not know what thickness was required for the manufacturer's installed gear.

Regards

Tim


Timothy Burchfield

Ray, see my post above to Steve regarding the thrust washer. I guess it is time to go to the source (as far as I know) of the spacer information, Bob Grunau, to see if he can throw some light on where the spacer requirement came from.

Tim
Timothy Burchfield

It doesn't matter who supplied the thrust washer, it is there on all distributors ever made throughout history. Or at the very least on every vehicle I've ever owned.

I don't know what else to say about the spacer at this point. I see no evidence that it was not installed on every TD at the factory, nor any logic in removing it.
Steve Simmons

Steve, I was only pointing out an explanation for your commnet, "... and despite the lack of a part number, the thrust washer is absolutely necessary." So there is a logical reason for no part number for the thrust washer in the Lucas catalog (Lucas didn't supply the gear) but not one for a spacer. I'm still hoping someone can come up with some official documentation for the need for the spacer. The lack of which is very odd.

Regards

Tim
Timothy Burchfield

Common sense suggests that the gear and spacer ring would be transfer items, intended to be removed from the old distributor for transfer to the new one. Seems to me that it's like any other model-specific part where there is any sort of bracketry attached, that would be removed from the worn-out part, and re-installed on the replacement one. I'm not surprised that there is no number for the spacer ring; I think the thrust washer is very probably the washer between the gear and the tube, or perhaps one inside on the shaft to properly align it.

Tom Lange
MGT Repair
t lange

Tom, I would agree if we were just talking about moving one distributor to different car. But the 40162 was a new distributor in a new car not a transfer. I still haven't found any evidence that a spacer was supplied by Lucas or MG when the micro adjuster was eliminated and the different distributor (40162) was introduced.

Regards

Tim
Timothy Burchfield

I did a picture and measurements on my distributor


Bruce Cunha

https://www.mgexp.com/forum/t-series-and-prewar-forum.46/distributor-spacer.3516034/

https://www.mgexp.com/forum/t-series-and-prewar-forum.46/spacer-ring-under-distributor.3927266/
Gene Gillam

Bruce, thanks for posting. Those measurements match the 3 40162 distributors I have.

Regards

Tim
Timothy Burchfield

I just noticed something interesting, the hole to attach the early TD distributor clamp to the block is slotted. It can be raised and lowered. This would allow you to raise the distributor 1/8" and with the thickness of the clamp (1/8") you would have your 1/4" that a spacer would provide. I'm not convinced it is necessary but perhaps thais was how MG addressed the loss of the micro adjuster thickness.

Tim



Timothy Burchfield


The engine block is threaded for the distributer lock bolt(spigot bolt). This bolts spigot end engages in the circular groove cut in the distributer boss and prevents it from moving up or down. The clamp with its oblong over sized hole has nothing to do with the distributer installed height. The clamp prevents the distributer from turning, to change timing, once the clamp bolt is tightened.
Richard Cameron

Richard, I have to disagree with you. The bolt going through the clamp into the block does not have any effect on the rotation or removal of the distributor. With the clamp securely mounted to the block you can still insert, remove and rotate the distributor. It is the horizontal bolt and nut that close the clamp to keep the distributor from rotating and moving up or down. You can raise the distributor 1/8" by placing it in the clamp and loosing the bolt in the block. Raise the distributor and clamp 1/8" and re tighten the bolt. The distributor is now 1/4" above the block (the new clamp height and the clamp thickness). The clamp stays in the same position against the distributor body. I have done this on my car and it worked perfectly.

Tim
Timothy Burchfield

Here's a picture of the clamp in the raised position. Notice the wear marks on the vertical part of the clamp where the block bolt had previously been tightened at a higher level.

Tim


Timothy Burchfield

Surprised this thread is still active.

"From Dave Braun, Minnesota, USA

This clamp? The hole is elongated vertically. The shouldered bolt stops on the shoulder against the block, and the pin goes into the square groove around the mounting boss but does not touch the boss, allowing the distributor body to be turned when the other clamp bolt is loosened, but preventing the distributor from going more vertical than the elongated hole allows.

The clamp "floats" allowing for small machining errors in the distributor. Do not over tighten the clamping bolt as this can crack the distributor housing. Because of the clamp design, a separate ground wire is needed."



----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

"allowing for small machining errors in the distributor" includes:

"Distributors can be damaged and even engines can be destroyed after an engine rebuild because of improper distributor-gear selection, fitment and gear/drive meshing.

There are several trouble areas that may arise. First of all, it is imperative that distributor shimming heights are correct, meaning it is critical for the distributor gear to be centered to mesh properly with the cam gear. If this is not done, a process called “knife-edging” will occur and the drive gear will be damaged.

Problems with irregular distributor gear wear can be caused by the distributor drive being “bottomed” out. Check for proper installation by applying machinists dye to the distributor gear. Spin the engine by hand several rotations. Remove the distributor and inspect the wear pattern. You should have an even pattern through the middle of the gear. If this is not the case, add distributor shims until the correct pattern is obtained.”
WHT

WHT, Braun states that the distributor can raise vertically, "...but preventing the distributor from going more vertical than the elongated hole allows." So the elongated hole allows the distributor to be raised.

Tim
Timothy Burchfield

I'm also surprised there is still any question about this. Richard and Bill are both absolutely correct. The clamp is to prevent rotation and has nothing to do with distributor height. The height is adjusted if necessary by shimming.

The clamp is not a precision made item, it's just a piece of stamped steel. There is little doubt that the elongated hole is there to allow the clamp to line up with the block without precision machining of such a low cost part. An elongated hole will also do the same thing here as in many other places - to account for casting or machining error in the block or other components. For further reading, look into "core shift" as well as differential gear adjustment and why it's so important to get it right. It's the same concept here.
Steve Simmons

Ok guys, opinions are fine but facts are the only thing that matters. I have used the slot in the distributor clamp to move the distributor 1/8" up in it's bore. That combined with the thickness of the clamp has provided the 1/4" spacing so many of you are so passionate about. When the horizontal part of the clamp is tightened The distributor does not rotate and does not move vertically in the bore. Despite the comments that it won't work it does. I would refer you back to the picture above showing the 1/8" space between the clamp and the block. You know what they say, none are so blind as those who will not see. :-) Bottom line, using the slot allows you to raise the distributor. I've provided photographic proof. If you disagree provide the same.

Tim
Timothy Burchfield

Tim,

The bolt holding the clamp has a shoulder which locks against the block WITHOUT locking the clamp. If you don't have this then you have an incorrect bolt. With the correct bolt the clamp can move up and down because of the slot, but cannot rotate.

John


J Scragg

John, if the bolt in the block did not lock the clamp against the block then the distributor could rise and fall the length of the slot during operation. Surely you don't think that was the purpose of the design? The sacred 1/4" space would vary due to the distributor's vertical movement. I have the correct bolt and it does lock the clamp to the block. I believe the shouldered bolt is to prevent the clamp from being pushed off of vertical thereby preventing the clamp sitting flat on the block opening.

Tim
Timothy Burchfield

Tim,
The same shoulder bolt also has an extension on its front end which fits into the circular groove in the distributor shaft, thereby preventing any vertical movement of the unit.

John
J Scragg

John, I don't disagree with your statement. But I went out and removed the bolt the distributor and the clamp. I reinserted the distributor in the clamp and ito the block. I positioned the clamp approx 1/8" above the block and tightened down the block bolt (double checked that is the correct one). The clamp is still above the block by approximately 1/8".

Tim

Tim
Timothy Burchfield


With Spacer ring


Richard Cameron


Another Photo


Richard Cameron


3rd Photo


Richard Cameron


Last photo


Richard Cameron

Richard, according to your photos the spacer ring is not needed since the distributor will always be in the same location relative to the slot and the bolt in the block.

Tim
Timothy Burchfield

The thin metal bracket holding it up the air will crack from vibration without being supported. That will likely allow the dizzy body to vibrate and move around in the block with ultimately bad results. Wish I could use a phone emoji here....George
George Butz III

George, in Richard's example with or without the spacer the clamp stays on the block. the pin of the bolt holds the distributor shaft tight in the block bore. Imagine taking out the spacer in one of Richard's photos and you'll see that the distributor stays above the clamp because of the location of the pin in the groove. And besides, I would hardly call a 1/8" thick steel piece a thin metal bracket.

Regards

Tim
Timothy Burchfield


Tim, one last input: Refer to The midget Workshop Manual Page C.8, Fig. C.14. This explains how it is suppose to work.

Yes, the distributer will be in the correct vertical location if the installer makes sure the lock bolt spigot engages the circular groove on the shaft boss, but there will be a slight gap under the distributer base. Further, like you said, the clamp oblong hole allows some play up and down too (about 1/16").

The spacer however, provides a solid base that never changes and ensures the lock bolt always engages the groove in the boss. Since some don't know there is a reason for the design of that lock bolt, without a spacer, there's always the probability they would just push the distributer all the way down which is about 1/8" too far. Then when they tighten the lock bolt, it wouldnt be in the groove correctly. Tim, there are so many spacers out there in use, I can't believe someone made them all and sent them around to MG owners behind my back over the last 56 years.

However, If you are so dead serious about not using a spacer because someone from ? ? may have invented it "not MG", by all means don't use it!

I promise I'm not being mean spirited, I have always enjoyed helping other MG owners, but like you said---"You know what they say, none are so blind as those who will not see."
Richard Cameron

Richard,absolutely no offense taken. Thank you for your informative posts.

Regards

Tim
Timothy Burchfield

Not to confirm or deny either position, only what I have.

Disclaimers.

1) This is a replacement engine(16052 from TD 15590, should be 13135). History unknown.
2) By 1969 it needed a rebuild BAD, although my odometer was only 44400.
3) My son and I took it apart in 1983, rebuild took place over '83, and '84.
4) We did a very poor job of documenting things.
5) The bolt holding the bracket looks correct. It has a head drilled and seems to be anchored.

I was working on oil leaks and decided to see if I had this spacer.
No.

But it could have been left out during rebuild or before I got it. Without loosening the bracket fixing bolt the distributer is free to turn if the locking bolt is loose, sot the fixing bolt does not touch the distributer internal shaft, but must sit in the grove.
Note the gap above the bracket. Is it 1/8"? looks smaller but perhaps 3/32"
Close enough that I don't think I am not going to add one unless I take the distributer out of the car in the future.

HOWEVER:
If anybody has the OD and the ID dimensions I would appreciate it.

BTW that magic shoulder bolt lists for $35 (433-530) at Moss.

Jim B.



JA Benjamin

Jim, sorry for adding this post. I looked at your picture for several days and finally decided to add comments for the benefit of a new person who might read this thread in the future. All of us have been there at one time looking for information.

The distributor clamp being discussed, and the distributor, are designed to float a small amount vertically, but NOT allow any rotation of the clamp and distributor that would affect timing (hence the vertically oblong hole in the clamp). This “floating” action is especially important when using cams that require VERY high valve spring pressure not envisioned by XPAG designers (flexing and gear mesh).

For that reason, the shouldered Lock Bolt 23 should be installed WITHOUT an exterior washer as seen in the above picture that would lock the clamp to the block and apply pressure to the side of the distributor body. This defeats the purpose of the clamp design and it is not the best location to place a ground wire. Because the clamp and distributor can float a small amount vertically, the distributor NEEDS a ground wire and it can be run from the bolt that locks the clamp to the distributor body to a suitable location on the block.

Previously Discussed Background: Regarding the shouldered Lock Bolt 23, this should normally NEVER make contact with the distributor body. It only makes contact with the body when the much discussed 1/8-inch spacer ring is missing and the interior end of the bolt rest on the bottom edge of the groove in the body of the distributor or is smashed against the distributor body. When installed correctly (as Steve, Ron, Richard and almost everyone else has said) the weight of the distributor rest on the spacer/clamp/block and the end of the Lock Bolt is positioned within the groove on the distributor body, but NOT touching the body or edges of the groove as shown in previously posted pictures. The bolt was designed to use lockwire to prevent it from unthreading.

The PO of my wife’s TD omitted the 1/8-inch spacer and Lock Bolt 23 made contact with the distributor since the groove was now below the end of the bolt. He then tightened the bolt to lock the distributor in place; smashing and damaging both of them. Her TD now has the correct spacer and the distributor “floats” vertically as intended. The engine is strong and runs very smoothly.

If there are errors in what I have posted, please make corrections as needed.



WHT

Bump for Bruce

See the bolt

Jim B.
JA Benjamin

There are two different shaft lengths in distributors fitted to Y-Types, which were produced alongside the TC.

The Tourer has a long shaft & a 0.125" spacer, as the YT did not have the micro-adjuster as fitted to the TC despite having the twin carb engine.

The Saloon (XPAG single carb) has a short shaft dizzy and requires no spacer to ensure the correct alignment of the dizzy drive gear with the camshaft.

As you can see, the slot for the lock bolt is the same distance from the drive gear in both dizzy types. Both have the simple lock plate as was eventually fitted to the TD some years later.

I hope this clarifies some of the confusion some people might have with the various XPAG distributors and their mounting height.

Tony Slattery
The Classic Workshop
Black Mountain
Australia



A L SLATTERY

This thread was discussed between 29/08/2019 and 04/11/2019

MG TD TF 1500 index

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