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MG TD TF 1500 - Distributor Cam orientation.


This weekend whilst diagnosing what turned out eventually to be a fuel problem I had the distributor in bits to change points, condensor etc.

I thought the weights felt a bit "sticky" so took them out to polish them up a bit so they moved against the distributor base plate smoothly.

I reassembled everything but couldnt start the engine. It kept backfiring through the carbs which (to me) indicated the leads were all connected wrong.

I checked and rechecked but couldnt figure what was wrong. Started to replace components but got nowhere.

Eventually I buried my way back into the distributor and wondered if the high lift cam was 180 degrees out. I assumed it could only go in one way. I was wrong. I unscrewed it and turned it round, put everything back in and she fired up first time.

3 and a half hours it took me to learn that lesson.
Doctor Bob

When I pull a distributor out of an engine, I take a marking pen and put a dot or mark the top edge of the housing in line with the rotor. Backing up the shaft about a quarter of a turn before installing it back in the engine, it will turn back to it's proper position when meshing with the cam gear. Never fails. PJ
Paul S Jennings

Useful post Dr Bob. Nice title too. Cheers
Peter TD 5801
P Hehir



For clarity I show a picture of the Cam. If you undo the centre screw the cam can be simply lifted off the weight pivots. Its easy to put it on the wrong way round.



Doctor Bob

I remove the cap and take a photo of the position of the rotor with my iPhone before I remove the distributor. Sit the phone on the valve cover with photo on the display for fast/easy reinstallation - assuming that the crankshaft hasn't been moved.

Lonnie
TF7211
LM Cook

I think Dr Bob is talking about ensuring the dizzy is reassembled correctly after tear down, ie ensuring that the high lift cam is not reinstalled 180 degrees out of whack. Paul & Lonnie's suggestions deal with reinstalling the dizzy in the car. It is possible to install the dizzy 180 degrees out of phase which would presumably produce the same symptoms that Dr Bob experienced. I've now added the high lift cam to the growing list of bits that can easily be fitted backwards on a TD. Thanks Dr Bob. Cheers
Peter TD 5801
P Hehir

I recommend replacing the springs with weaker springs for full advance by 3,000 RPM, also re curving the advance curve for 12-14 degrees advance static, engine off.
You want a total advance of 36 degrees @ or before 3.000 RPM
I offer this service as well as many others.
Len Fanelli
Abingdon Performance
XPAG Roller lifter Camshafts & roller rocker arms.
A roller lifter camshaft will always out perform a flat lifter cam of the same duration with no cam, or lifter wear!
From stock to full race.
914 420 8699
laf48@aol.com
Len Fanelli

Are businesses permitted to advertise on this forum? I thought that was considered bad form?
Peter TD 5801
P Hehir

This thread was discussed between 26/08/2014 and 28/08/2014

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