TR6 Limit Mechanical Advance on TR6 distributor?

[Rocky_LC]

I am running triple Webers on my 1971 TR6 engine, with approximately 9.5 : 1 compression. Pertronics module on a Lucas distributor.

The Webers like LOTS of timing at low RPMs, and I’d like to limit the timing from the 13* available so I keep the “all in” timing to about 34-34*

My preferred method would be something easily reversible, like on Ford distributors, where you can just put heat shrink tubing over the limit stop tabs.

Would like the thumbwheel adjuster to continue to work!

Pictures would also help me visualize the mod…

Thanks -

Rocky

 

[Sarastro]

There are probably simple ways to do this, but are you sure that's what you want? Setting the initial timing as high as you have will shift the whole timing curve upward, which may not be what you want. One possibility is to get the programmable 123Ignition distributor, and then you can create any timing curve you can imagine.

 

[Rocky_LC]

Yes, I saw that option, but they looked like they were about $600.

Trying to come up with an economical, old-school solution.

I did think the 123 solution is a good one with the ability to use both RPM and vacuum to affect the timing…

Thanks -

Rocky

 

[CJD]

I would likely first use a dial timing light to set the high RPM advance to the 34 degrees you want. Then see if the car behaves well at idle and low end. I would not include the vacuum when setting the high speed timing...then use it or not. For all out performance, the vacuum advance just gets in the way, and often results in a quick rattle on rapid acceleration. On a street car it will help with fuel economy at cruise.

If you do not get a good low end with this, then I would look at weaker springs to bring the timing in quicker. If neither of those work, then I would move on to restricting the range of advance like you are planning. Do the cheap and easy first to get some reference...

 

[Rocky_LC]

That seems like a good tuning strategy…. Makes a lot of sense.

Might have to upgrade my timing light!

I don’t have vacuum advance…. No ported vacuum on the Webers.

Thanks!

Rocky

 

[TR4nut]

A friend of mine has a similar setup to yours with Webers. He did something like the Ford truck you mention, I believe he used aluminum tubing and fit it over the stop. Sorry don’t have details or pics but enlarging the stop can work

 

[CJD]

With a little trig you can draw the proper chalk mark on your front pulley for the 34 degrees you are looking for. On a TR2/3 it comes to about 1/8" per degree...not sure what your diameter is on the TR6? I hate to buy tools when there is a work around, unless they are on sale, LOL! You could also use a degree wheel to find the proper location for a mark, if you have one of those to hold up to the front pulley.

 

[Rocky_LC]

Yep, I can also find the 34* by scaling the marks on the balancer…. I know I have TDC, 10* and 20* (and maybe 30*) etched on the balancer…

I haven’t taken the distributor out yet. I have seen the vacuum advance and thumbwheel adjustment on the plate that holds the points, but haven’t gotten any deeper into the distributor than that.

Thanks!

 

[Rocky_LC]

Here’s how I did it…. Made a spacer, 3/16” ID, .320” OD.

This limits my mechanical advance to about half of the stock capability of 13*, which is what I’m looking for.

Rocky