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TR2/3/3A TR3 Distributor Questions

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K

karls59tr

Obi Wan
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What is the procedure for testing the vacuum advance using a vacuum gauge? Is the pressure supposed to hold steady at idle and rise on revving? How many psi should it hold at? If the diaphragm had a leak would it gradually lose vacuum at idle? If there was a leak how would it affect perfomance at speed? CK
 
If you induce vacuum on an advance, you can check it with the engine off and at idle. First with the engine off, disconnect the vacuum advance line from the carb and block it to prevent leaks. Next hook up your gauge and pull a few inches of vacuum and just let it sit for a few minutes. If it doesn't drop or go back to zero, your diaphragm is not leaking.

Release the vacuum from the advance.

Next, start the car and and let it warm up, or better yet, do this after the car is already at operating temperature. Pull a few inches of vacuum. The engine speed will increase slightly, or with a retard unit, it will decrease slightly.

This will also test that the advance unit is working with the distributor. It does not confirm that everything is set perfectly, only that it is working.

Good luck.
 
If the advance has a leak, the performance may be erratic. You could get a stumbling or lack of power on acceleration.

On the other hand, if the centrifugal weights are sticking inside the distributor, the advance could be fine, but not effective.
 
Karl,

do you have a manual that gives the specification, if so using a strobe you can see if the advance corresponds to the vacuum figures using a vacuum source. One thing, the vacuum does not increase as you open the throttle and at wide throttle openings it has no effect whatsoever.

The important part of the distributor is the mechanical advance, which has far more effect on performance. You could disconnect the vacuum advance, and I bet you won't notice a performance loss.

Alec
 
I agree with Alec and Paul. One thing you might consider is taking your distributor out and dismantling it down to where you can check your weights. These things can get real gummy or dry, depending on how they are lubricated or not lubricated over the years. Clean everything well and use a non-gumming lubricant to free them up. A source of many poor-running problems is sticking weights in the dizzy.
 
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