[jotto]

Hey guys,

Well the rain stopped, I popped my hood and put my back out!
So now the sun is out and the Vette is away.

Whilst checking the timing, I noticed I got my 36 deg all in and fairly quickly. I didnt get a chance to map it but I reckon I must have fairly light springs in my dizzy.

So can someone explain the best kind of curve to have and why.

What happens if you get all advance in quicker at low revs right through...
What happens if the timing comes in later but before around 2800rpm.

The engine seems to be running fine with no weird noises so I guess its ok.

Just want to learn a little more about advance curves.
TIA.

 

[mrvette]

:rolling: All I know is from reading and some practical experience that goes counter to what I read, a bit....

most racers say to set initial by revving engine to 2500-3000 rpm, set the timing to 36-38 degrees, lock er down and leave it....seems that 1/2 the time it's at some silly number like 15-20 degrees advance doing that....
meaning the whole damn thing is way the hell off calibration....the engine starts fine when cold, not an issue, but when hot, it s WAY the hell too much advance...don't ask....:WTF

from all the messing around over years, I think to set the initial no higher than 8-10 deg, and dial in the cent advance to your total at ~2800 rpm and have done with it....apparently one heavy and one light aftermarket spring is about correct....I have found it necessary to either add or remove some rubber snubber washers under the dizzy plate stop pins.....too long now, I forget ...too many cars....chebby, olds, Pontiac, caddy, ford, mopar, I can't remember which is which, but the final results are similar...

I hook up the vac advance to full manifold vac, as doing that allows an rpm increase at idle, then you can close the throttle a bit more to drag it down some, this reduces the tendency to diesel on shutdown when hot...

that's about all I know, anything more comes from someone smarter....

I presume you do know what advance IS, and why....sorta leading the duck, kinda thing...

 

[jotto]

:rolling: All I know is from reading and some practical experience that goes counter to what I read, a bit....

most racers say to set initial by revving engine to 2500-3000 rpm, set the timing to 36-38 degrees, lock er down and leave it....seems that 1/2 the time it's at some silly number like 15-20 degrees advance doing that....
meaning the whole damn thing is way the hell off calibration....the engine starts fine when cold, not an issue, but when hot, it s WAY the hell too much advance...don't ask....:WTF

from all the messing around over years, I think to set the initial no higher than 8-10 deg, and dial in the cent advance to your total at ~2800 rpm and have done with it....apparently one heavy and one light aftermarket spring is about correct....I have found it necessary to either add or remove some rubber snubber washers under the dizzy plate stop pins.....too long now, I forget ...too many cars....chebby, olds, Pontiac, caddy, ford, mopar, I can't remember which is which, but the final results are similar...

I hook up the vac advance to full manifold vac, as doing that allows an rpm increase at idle, then you can close the throttle a bit more to drag it down some, this reduces the tendency to diesel on shutdown when hot...

that's about all I know, anything more comes from someone smarter....

I presume you do know what advance IS, and why....sorta leading the duck, kinda thing...

Lol...er...well...its just the kind of thing that I know how to set as per Lars paper etc but have never really known why.

I know the spark has to be timed just right to get maximum performance and that correct timing helps the engine run smoothly etc...

Its one of those things that I know I should check and set...but not really fully understood why. :smack

Saying that, there have been a number of posts recently that have made good reading...Norval's post on why he always uses a vacuum advance. Seems to be a few people that say they never run it....

I just set mine to 36 deg all in and lock her down as you say.
Just wondered what different curves would do with an engine.

 

[mrvette]

Lol...er...well...its just the kind of thing that I know how to set as per Lars paper etc but have never really known why.

I know the spark has to be timed just right to get maximum performance and that correct timing helps the engine run smoothly etc...

Its one of those things that I know I should check and set...but not really fully understood why. :smack

Saying that, there have been a number of posts recently that have made good reading...Norval's post on why he always uses a vacuum advance. Seems to be a few people that say they never run it....

I just set mine to 36 deg all in and lock her down as you say.
Just wondered what different curves would do with an engine.

My largest problem is somehow accepting what some guys say over setting for the max advance, and lock her down....doing that has for ME allways caused the thing to hard start when hot...

but far as I"m concerned, i'tl all moot anyway, cause for 12 years now, I run TPI and let the damn computer/programmer worry over it.....I have had some field days with operational problems, but nothing to do with the computer or programming....wiring was the problem....

:crazy: :devil: :devil: :cheers: