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Post by dave1800 on Mar 12, 2017 5:28:27 GMT
We are currently preparing detailed guidance to help Forum members tune their Crab engines. This will include important areas often overlooked in general tuning instructions. One of the key areas is to check that distributor advance curves are properly matched to standard and modified engines to ensure optimum performance and avoid serious engine damage. Details in the BMC/BL workshop manuals are incomplete in that the maximum advance which is a critical component was not published. To ascertain this figure it is necesary to identify the number stamped on the distributor cam (in camshaft degrees) and add this to the static setting. This number can be seen with the aid of a torch without dismantling the distributor by rotating the shaft until it is visible in the gap below the contact breaker plate next to the vacuum advance unit (it will probably be in the range 10-16 degrees). The distributor number is found on the outside of the body as shown in the photos below and may not be possible to read in the car in some cases. We would be very grateful if as many members as possible could let us know the following details by 21st March if possible so that we can complete the guidance. (Initial indications are that we may need several details for each model to ensure accuracy and detect possible errors due to internal component changes having been made). (a) the details of their car (Mk1, Mk11, Mk111, Mk11S, ex military LC) (b) the degree numbers on the distributor cam (accessible with the distributor in the car) (c) if possible the number stamped on the body of the distributor (this may not be accessible in the car)(d) whether the distributor has been changed or modified - if known.
Thanks in advance David (Photos from Marcel Chichak - Tuning the Lucas Distributor)
Distributor cam maximum degrees number - right hand side below primary spring 
Example of distributor cams  Distributor numbers on lower body  " |
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Post by 1800heap on Mar 14, 2017 10:55:48 GMT
Hi David Not sure how much use this is to you but my Australian Austin MK2 has 12 stamped on the cam and top line on the case is 62941097A bottom line is AYH 0576 3 69 unknown if this is original dizzy sorry. Thanks Nick Found this info in my Gregorys Austin 1800 service manual. Sorry about the bad scan. Distributor 1.pdf (336.9 KB) Distributor 2.pdf (313.46 KB) May or may not be helpful. |
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Post by Penguin45 on Mar 14, 2017 14:06:05 GMT
Hi Nick, good info.  I think David will like that bit.  Chris. |
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Post by foglaursen on Mar 14, 2017 14:39:55 GMT
These are the data for my Landcrabs: Morris 1800 MKI Year 1966 Engine original Distributor original Number 40969 H Date 366 Degree number on cam 12 Wolseley18/85 MKI Year 1967 Engine Wolseley MKII 1971 Distributor original for the engine Number 41234F Date 2071 Degree number on cam 15 Reading the degrees was not easy. Impossible to see directly. Tried with a camera, but flash light adjusted camera to the part near it, so the cam became dark. Ended up with a borescope attached to a PC. Peter  |
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Post by dave1800 on Mar 15, 2017 1:30:46 GMT
Hi Nick
Thank you for the information from your Australian Mk11 car. I have checked your details with an article published by Tony Cripps some time ago and confirm that the distributor 41097A is an Australian made 29D4 (not 25D4) with a top entry cap fitted to Mk11 cars from October 1968.
The 12 degrees distributor maximum advance is reached at 2,800 rpm after which there is no further mechanical advance. The static setting is 10 degrees BTDC giving a total mechanical advance (vacuum disconnected and plugged)of 2x12 = 24+10 34 degrees. This is quite a bit different from UK Mk11 cars.
regards
David
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Post by dave1800 on Mar 15, 2017 1:46:05 GMT
Peter
Thank you for the details of the distributors fitted to your Mk1 and Mk11 engines. I am sorry you had to go to so much trouble to be able to read the degrees number stamped on the cam. It is much appreciated. The boroscope cameras are just such a wonderful investment - I purchased a couple of cheapies from Ebay for around £12 for both - and they work fine. I've used them for multiple jobs around the house including tracking wiring and water leaks.
Your distributor numbers agree with what I had anticipated (for UK spec models)and the first Mk1 data I have received so far. This will help me try and unravel some apparent anomalies between Crab and MGB advance curves.
I am still hoping to get Mk11 "S" data. I have received details from two "S" owners but the first had a distributor from a 848cc mini with unknown internals and Gordon's distributor that he fitted to Chris' car recently turned out to be the one fitted to Mk111 Crabs and others but not the "S". (Both owners are now running 123 programmable ditributors).
regards
David
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Post by Penguin45 on Mar 15, 2017 9:32:53 GMT
I am still hoping to get Mk11 "S" data. David WM lists 41238A for the MkII S; a 25D.  Chris. |
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Post by dave1800 on Mar 15, 2017 9:48:11 GMT
Thanks Chris. I should have made clear that what I am missing is the degree number stamped on the distributor cam, probably between 12-15 degrees. This is needed to establish the maximum advance, a figure that should not be exceeded. The w/s manual fails to give this, but early MGB w/s manuals do. I am particularly interested as the advance curves shown in the w/s manuals for the "S" and MGB for the same period are way way different. My official BL w/s manuals dated 1971 and 1973 show different advance figures for the "S", not a lot but the other Mk1/11 details are unchanged so there maybe something odd that would show up when I plot them on a graph them - but I need the max advance figure to do this. David I am still hoping to get Mk11 "S" data. David WM lists 41238A for the MkII S; a 25D. Chris. |
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Post by tommydp on Mar 17, 2017 15:57:58 GMT
What will happen if you put a 40969 distributor in a mk 2 engine? I have one with no shaft play, compared to the 41234 one...
Will performance suffer?
Tommy
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Post by dave1800 on Mar 17, 2017 23:49:02 GMT
You would need to use the 41234 static setting of 9 degrees. The curves are almost the same up to aroind 4,500 rpm after which the 40969 will be a little retarded so you could lose a bit at the top end, if you actually go that high. You could try compensating if necessary by advancing the static setting to 11 degrees as long as it didn't knock. The vacuum units would need to be switched as the 40969 gives 20 degrees at 10" Hg and the 41234 12 degrees at 7" Hg or you would probably get knock at low / medium engine loads. Let us know if you try it! regards David What will happen if you put a 40969 distributor in a mk 2 engine? I have one with no shaft play, compared to the 41234 one... Will performance suffer? Tommy |
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Post by Ben N on Mar 19, 2017 2:40:51 GMT
Hi David,
I have a Canadian 1971 Austin 1800 mk11. It has 41234 F stamped on the distributor (and 03 70 below) and 15° on the cam. I don't have a full history of the car so I couldn't say for certain if it is original or not.
For Nick's request, my 2nd engine prefix is 360B.
hope this helps,
Ben
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Post by dave1800 on Mar 19, 2017 7:36:52 GMT
Thanks Ben 41234 was the UK distributor for Mk11 Crabs with the 9.0:1 compression engine and 0370 means it was made in March 1970. I don't yet have any data as to whether the "F" is significant. The 15° is consistent with the distributor body number. I am aware that Canadian Crabs switched to bias needles earlier than the UK but that didn't bring about a change in the advance profile. It look as though you most probably have the correct distributor. regards David Hi David, I have a Canadian 1971 Austin 1800 mk11. It has 41234 F stamped on the distributor (and 03 70 below) and 15° on the cam. I don't have a full history of the car so I couldn't say for certain if it is original or not. For Nick's request, my 2nd engine prefix is 360B. hope this helps, Ben |
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Post by 1800heap on Mar 20, 2017 21:51:51 GMT
Thanks for your help ben I will let you know what the info says about you car.
Regards
Nick
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