TR6 TR6 Distributor mechanical advance question

[TR6oldtimer]

Here is a picture of the mechanical advance out of a '73 TR6. Notice the 16 stamped on what I will call the advance stop. I have another distributor I got years ago from TRF and it has a 13 stamped in the same place. The question is is my assumption correct that each limits the mechanical advance, and if so, is there a preference? The engine has a GP2 came.

 

[TR3driver]

I can only answer half the question: Yes, that stop is what limits the mechanical advance.

If you are running the stock compression ratio, then I assume most likely the motor would tolerate some more advance. But that's strictly a WAG, worth no more than it costs.

 

[Brosky]

Ray,

Those advance springs should be exactly the same. If one is stretched more than the other in a retracted position, the advance may not be what it was intended to be.

And the 22D distributor that I had that the housing was stamped 1975 had 13 stamped on the plate.

 

[TR3driver]

Those advance springs should be exactly the same.

It depends on the particular model of distributor, but for most Triumphs the springs were different. This gives the advance curve two different slopes, a more rapid increase at lower rpm and a slower increase at higher rpm.

I show two different distributors used in 1973 on US-spec TR6, one limited to 13 (cam) degrees advance @ 2500 (cam) rpm, and the other 10 @ 1850

 

[Brosky]

I stand corrected Randall. I was not aware of that and had only seen matching springs in my GM days, so I assumed (incorrectly) that these should be the same. Thanks for pointing that out.