Plan on rejetting the Edel perf. this weekend. If I got time, plan on recurving the dizzy, currently stock with a pertronix unit and adj vacuum advance. understand the objective is36 deg total by about 2800-3000 RPM, initial + mechanical. What should thevacuum advance be at once the mechanical is set, and locked down?

 

would be great if you'd find out.
initial+mechanical: yes, that's the plan (at least mine)

To the vacuum advance i usually get: trial and error ...
in any case at full throttle there's no vacuum so vac advance is 'only' for fuel saving and streetability

kalli

 

Yep, that's the way I understand it. Your vacuum will be zero at WOT, so there will be no vacuum advance. Vacuum advance is really only until the mechanical advance takes over when the engine is off-idle.

 

Cruise mixtures are normally leaner than WOT mixtures, and lean mixtures burn slightly slower than richer mixtures. So you need to get the fire started a little sooner in order to get the best use of the fuel during cruise.

My understanding is that if it 'pings' during cruise or at the beginning of really gentle acceleration, you've either got too much vacuum advance or the vacuum diaphragm can't move quickly enough toback off some of the vacuum advance. An adjustable vac advance mechanismis sometimes required.


Norm

 

You are asking questions that the answers are probably in some 1970's hot rod mag. Give a shout to a local hi-po shop and see if they know. Perhaps there's a "how to hot rod X-block Fords" article. Sorry if this is not much help.

 

the dizzy was set for 13L and factory springs. Went to one lighter spring, and set initial. Rejetted primaries, one step richer, and changed spring (pink). set inital to 10, mech reads28, total 38 by 2800 RPM. I was expecting to feel a little more seat-of-your-pants punch, but all together, I'm pretty happy. Definately noticed the sprint change made for asmoother transition between the rpm and advance. Get a very momentarypingingat WOT, foot to the floor. Backed off the vacuum a little more. Plugs tell me I'm running good but a touch lean, so I'm gonna throw in a colder plug and maybe a jet change in the secondaries. not bad for 87 octane. Thanks for the input guys.

 

sounds good what you're doing here.
had to change one of the springs as well, as my mech advance didn't kick in until 1700
I'm at 9degress initial and around 38 at around 2600 as well (seems to max out here) altough I don't have a holdback installed.
I'll check again when the neighbours are out of the house. must annoy the **** outta them revving at 3000+
I'll have to recheck on my plugs as well at some stage
what annoys me I never heard an engine ping. you know once you hear and identify a sound you hear it again and again and again. but I wasn never able to identify pinging which makes this very very hard to tune :-( In another post someone (jlt?) told me what it should sound like. I'll go for something like 14deg initial and listen out again. maybe that helps identifying the sound
]
kalli

 

Too much static timing just makes it harder to start (when the first couple of cylinders fire there isn't enough rpm's happening and part of the power strokes actually kick back against the starter and beat it up). I don't know if 14° is too much or not, just that at some point you get the above effect.


Norm

 

Thanks Norm,

yes I had that effect before, I don't want to have the 14degrees constant. Just to see if I can finally hear pinging. if i can identify it it would help me greatly I believe.
then of course retard again