kalli

Hi all,

I am currently using a pertronix distributor. Initial timing set at 16 degrees.
I had it with a light spring and a medium spring. And the total timing went up to 40 degrees. (all with vacuum disconnected, total centrifugal advance around 24degrees)

Now I put a limiter on one side, that the total timing doesn't exceed 34 degrees (total centrifugal 18).

My seat of the pants dyno feels complains that it ran better before (just a feeling) ...

I know that 40 is theoretically too far, should rather be 32-34. but what could affect it so that I seem to have a bit more advanced timing than that? i might try 38?!
petrol station claims 95ROZ

I am aware that I should not be so lazy and read spark plugs ... but it's either I don't have time or it's wet out if I do ... :-(

67 evil eleanor

How about 34 and VERY light springs assuming that the initial is right?

KMatch

What toys do you have available to measure acceleration with? Any cell phone apps? You might do better to find something to measure rather than seat of the pants, because that can be psychological. Your mind tells you 34 has less power than 40 so that's what you feel when you drive it.

How about rate of advance? 34 may be the sweet spot - and you're crossing 34 at max torque rpms on the way to 40 past peak whereas with 34, you're not maxing timing until after peak torque as you may be crossing 28-30 at this point. Make sense? Check your curves as well as rate of advance. You may do just fine with 34 but just need to get it in there quicker.

kalli

thanks lads. I'll try that. will try and keep it at 34 and just ramp it up quickly
16 seems right. easy start (no whoooop - whoooop ...). nothing else I can really judje it on

edit: i do have dynolicious and a g-tech (just have to find the cables ...)
i was just thinking that with redline at 6200 (currently) i should be constantly at max advance throughout the entire run.
so it shouldn't matter about the curve really ... but will check on that as well (when is full advance in).

should really do a run, adjust, run again, adjust ....

kalli

that idea with the weakest springs didn't work. they were so light that it was already advancing by nearly 14 degrees at 1000. I thought well use it but when I retarded timing so it would go back to around 16 the rpms went down and the whole lot dropped then as the centrifugal advance went again ... it's a bit too much out of control for my taste.
Put it back to what I had it at and will check with some gforce dyno to see where the sweet spot is and go from there

67mustang302

Take it to a track and find out for real.

With those heads you shouldn't need more than about 36.

kalli

would absolutely love to put a helmet on, but tyhe only drag strip I know close is in England (Santapod). I have ordered a MSD 6AL in the UK yesterday so I can finally fit my Crane distributor (about time). Once that's fitted I'll go from there.
I was invited by a friend in UK to come over to meet his tuner (dyno). But I don't think that's gonna happen anytime soon either :-(

urban_cowboy

Kalli, most race engines run no advance. In other words they are fully advanced at idle. The only real reason I know of for mechanical advance is to help starting the engine easier. I have a fairly fast curve in my car...all mechanical advance in by 2800. If I remember right, I am running 36* by 2800 and then I have vacuum advance on top of that. If you do not overheat at low rpms (more heat in chamber due to earlier ignition), a fast curve should not hurt you.

kalli

good to know and I've heard similar before. I find the further I advance at idle the less problems I have with engine heating as well. if i have let's say 12, then the idle temperature is way higher (starts climbing) from 14-16 on it stays at a certain low point.
Will definetly get back to it for the fun of playing around with it. But I thought with the box arriving next week and new distributor on top of that I'll leave it be for the moment. I'll get back when I swapped ignition parts with tests and numbers :-)

But from what you are all saying I'll try with a light advance curve.
As for what you are saying with the race engines:
a) race engine is never below 3000 (maybe even 5000) so there's no need for the mechanical advance. always all in
b) the vacuum advance saves petrol at cruising speed as it further advances at light load. at WOT it's off anyway. I find it rather (excuse me) stupid to not have one on a street driven car (apologies again) ;-)

Kalli

dodgestang

I've run with my advanced locked on my 410 cleveland for a long time.
Gets the same fuel mileage with or without the advance