TR4/4A Distributor rebuild?

[BL50]

I'm rebuilding my '66 TR4A that I bought in 1967 and drove throughout college until it just about rusted out from under me. I disassembled it back in the 70s and then life got in the way. Now that I'm retired I'm rebuilding. It's got 69,000 miles on the engine which I already rebuilt with 87mm pistons & liners. I've read a lot about people sending their distributors off to be rebuilt. This may be a silly question but when do you know that your distributor needs a rebuild? Should I just do it anyway - or can I just clean it up and save $250?

Thanks in advance for opinions.

Brian

 

[TR3driver]

Most common symptom is spark scatter; but the centrifugal and vacuum advance mechanisms can also fail.

For the first two, just hook up a timing light and watch what the timing mark does as you first let the engine idle, then slowly rev it up and back down. The timing mark should appear steady at all times, not jumping around, and should move smoothly as you rev the engine up and down. (To 3000 rpm or so, no need to go higher. Depending on which distributor you have, it may stop moving above 2500 rpm, that's OK too.)

If you have a vacuum source (like a MityVac), you can apply vacuum to the advance module and again watch the timing move. But if not, it's probably good enough to just suck on it (through a length of hose) and see if it leaks.

Obviously, these are just basic tests, but they pretty well cover all the common problems.

 

[arcom]

Since you have gone to larger pistons, a dizzy rebuild by Advance Distributors will provide an enhanced advance curve which will take full advantage of your engine mod. I had mine redone for a cam mod and the difference was noticeable.

 

[Marvin Gruber]

With only 69k on it you should be fine, otherwise stick a pertronic ele ignition on it and go.
Marv

 

[BL50]

Thanks guys!