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MG Midget and Sprite Technical - 1500 Timing Question

My Clymer Shop Manual says to disconect and plug the vacume hose to set the timing on my 76 1500 (w/o catalytic converter). When I do this the timing goes way off and the car runs rough. It runs great if I set to 2 ATC with the vacume hose connected.
The car has an electronic ignition put in by previous owner.(don"t know if this makes a difference.

The reason I am working on the timing is I am getting run-on I can't seem to stop. I use high test shell gas.

Does anyone know if the vacume hose should be disconected and pluged or am I getting wrong info from the manual I am using?

Thaks for any ideas.
JMA ANDERSON

Disconnect and plug vacuum line
set idle at or under 600 rpm (very important)
set timing to 10 BTDC, not 2 ATDC

see if that cures what ails you.
Richard Reeves

Thanks for your help-- the only question I have is the 10BTDC-- the sticker on the car says 2ATDC. Is there a reason for the difference?
JMA ANDERSON

JMA,
The vacuum advance on your distributor is actually a vacuum retard. All advance is done by the centrifugal weights. The vacuum retard is only active at idle and the vacuum port used is manifold vacuum and should not be used for vacuum advance. The only purpose for this was an attempt to comply with the letter, not the spirit, of emission regulations at the time of manufacture.

You can safely dispense with this feature today. Just plug the vacuum connection at the carb/manifold and set the timing at 10 BTDC at 600-800 rpm.

For run-on, check for a leaking carb or excess carbon in the cylinders. Timing shouldn't be an issue unless it is way off.
Lee Fox

2 ATDC is for cleaner emissions output, not performance.
10 BTDC is the otherwise standard setting for the engine.

FWIW my 1979 has vacuum plugged, and is set at 16 BTDC.

Tons of torque in the 1800-3300 rpm range where I drive it most days.

Easy enough to change it then drive it and see what feels correct to you.

Richard
Richard Reeves


Here is the data I have on 1500 timing.

Model Strobe Timing
1500 1975 UK only: 2 ATDC at 800 rpm
1500 1975-77 All other markets: 2 ATDC at 800 rpm
1500 1978 on Fed. US/Canada: 10 ATDC at 800 rpm

Are you sure your motor isn't perhaps a 78 engine? I have a 75 midget but its running a 78 spitfire motor. I had set it at 2 ATDC initially and had similar problems. Advanced it to around 12 ATDC and had significantly more performance and ran smooth.

I thought the 1275's ran more BTDC while 1500's ran ATDC. I would try going upwards on ATDC before backing off and moving to BTDC.

Might want to ask a engine expert what their thoughts are:I hear good things about "Hap Waldrop". He runs mg specialty shop. His website is: [www.acmespeedshop.com]

Good luck by the way let us know what you find out.
Thor Patterson-Ritz

Thanks for the information-- I will experiment with different settings and go with whatever makes it run the best.
JMA ANDERSON

This thread was discussed between 19/06/2010 and 27/06/2010

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