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MG MGA - check vac. adv @3000rpm

Gentlemen
I have an 1800 and I want to check the vac adv @ 3000rpm. I don't have an adjustable timing light. I was thinking If I set the mark on the pully to 10deg then measure the distance to TDC and mark the pully twice that distace counterclockwise. When I rev the engine to 3000rpm the new mark should be at TDC. Is this correct? I should be able to check the curve at differnt engine speeds this way also.
Thanks
Kris
Kris Sorensen

Kriss,
I have the same problem and the answers are in the thread Carbs or Timing. Let me know how you make out with your car and I will keep you posted on my attempts to solve the problem. Gord PS: My car runs a 1500 engine
Gordon Harrison

Kris your assumption is correct. It sounds like the method you suggest is proper.
Randy
R J Brown

Kris. It is the mechanical advance you check at 3,000 rpm, not the vacuum advance. You want a total mechanical advance of about 32 deg BTDC at that engine speed.

Mechanical advance is checked at any steady engine speed by applying a vacuum source to the vacuum advance can and making sure that it is advancing. The best source of the vacuum is one of the hand operated vacuum pumps like the Mighty Vac which has a gauge to allow you to see how much vacuum has been applied and whether the diaphram in the vacuum advance can will hold pressure properly. The can should be marked with something like "5-13-10" which indicates that the vacuum advance begins at 5" of mercury, the full advance is reached at 13" of mercury and the overall advance is ten degrees. I believe the degree specification on the vacuum can is given in crankshaft degrees rather than distributor degrees. (Distributor degrees being one half as much as the crankshaft degrees. Or, crankshaft degrees are twice the distributor degrees.)

Les
Les Bengtson

This thread was discussed on 17/10/2006

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