Setting Timing and adjusting vacuum advance canister?

[Don Gould]

How did we get to carb adjustments to correct the timing events?????
Without testing I would say the Vac can isn't holding so it's probably got a leak.
We have a way to set limits on the vacuum can stroke and we have Vac Cans that can read down to 8-10" of vacuum. If you need it any less than that you probably should be running a all mechanical distributor or get a valve job done.

 

[91r/t]

Sorry to respond so late, but my carb is set up alot better now. The motor is newer so no valve job needed. I was wrong in the way I was hooking up the vacuum gauge and testing the canister. I got that ironed out. I need to add timing to my car at idle and slow cruise as it is running fat and the headers are getting a bit warm. I can see a couple start to glow a bit but not much under steady 2000 rpm throttle in my garage when I was burping the coolant system for air. NO, the car is not lean, as the plugs are sooty as **** and the electrode is dark brown on the cylinders that are glowing. I jetted down two sizes on my primary and adjusted the idle and got it to burn a bit cleaner, but I believe it is actually running fat and needs a bit more timing advance at idle and light throttle. I am set at 19 degrees idle and 35 total without any vacuum. Any more timing at idle with the mechanical setting, and the car has trouble starting while warm or hot. I am going to use the advance of the vacuum canister to get some more timing at idle. The only other way would be a timing retard button for starting and I am not going that route.

 

[Don Gould]

Your correct that's what the vacuum can is supposed to do...Pull timing at idle and part throttle cruise.
The adjustment feature only adjusts the sensitivity of the diaphragm and not the stroke. you need to try and get the can set so at idle it will pull the timing up to about 28-32* pulling from a constant manifold source. If the stroke is too long it will go into a lean miss so you may have to limit the amount of the stroke.... We need to do this on almost every performance application.
Once you get the distributor set up correctly your black plugs and rich idle will go away.

 

[91r/t]

Yup that's what I was my thinking. About 28 to 30 at idle. It's why race motors lock at full timing and they run better with their fat setups fuel wise. I just can't get it to start worth a crap on warm days so using the can to add some timing doesn't seem like a bad thing. I think the can is set to 12 in/hg so that will be perfect for a 30 idle timing when the mechanical is set to 18 degrees.

 

[lewtot184]

Sorry to respond so late, but my carb is set up alot better now. The motor is newer so no valve job needed. I was wrong in the way I was hooking up the vacuum gauge and testing the canister. I got that ironed out. I need to add timing to my car at idle and slow cruise as it is running fat and the headers are getting a bit warm. I can see a couple start to glow a bit but not much under steady 2000 rpm throttle in my garage when I was burping the coolant system for air. NO, the car is not lean, as the plugs are sooty as **** and the electrode is dark brown on the cylinders that are glowing. I jetted down two sizes on my primary and adjusted the idle and got it to burn a bit cleaner, but I believe it is actually running fat and needs a bit more timing advance at idle and light throttle. I am set at 19 degrees idle and 35 total without any vacuum. Any more timing at idle with the mechanical setting, and the car has trouble starting while warm or hot. I am going to use the advance of the vacuum canister to get some more timing at idle. The only other way would be a timing retard button for starting and I am not going that route.

I use a light primary advance spring. my initial is 18 but idle is 26 due to the centrifugal advance starting quickly. this works very well for me.

 

[lewtot184]

Your correct that's what the vacuum can is supposed to do...Pull timing at idle and part throttle cruise.
The adjustment feature only adjusts the sensitivity of the diaphragm and not the stroke. you need to try and get the can set so at idle it will pull the timing up to about 28-32* pulling from a constant manifold source. If the stroke is too long it will go into a lean miss so you may have to limit the amount of the stroke.... We need to do this on almost every performance application.
Once you get the distributor set up correctly your black plugs and rich idle will go away.

are you the FBO Don?

 

[Don Gould]

are you the FBO Don?

Yes

 

[91r/t]

How do you limit the travel of the arm? Add a stop to it somehow?

 

[lewtot184]

Yes

cool! I need to send you a PM.

 

[lewtot184]

How do you limit the travel of the arm? Add a stop to it somehow?

I put a shim/spacer between the notch in the arm and canister body. i'm thinking a degree is about .010"-.012". I do this on one of my cars. seems like limiting total advance, including vacuum, to around 50 degrees makes my car cruise smoother.

 

[Don Gould]

How do you limit the travel of the arm? Add a stop to it somehow?

Yes, but that's one of things we consider Proprietary information.... if we gave away all the techniques that we've learned over all these years we wouldn't be able to pay the bills.

 

[91r/t]

Ok, well if I have a 12 degree advance canister and my total mechanical is set to 35, then I will be at 47 total timing in theory. I will check it with the light obviously, but I should be ok.

 

[91r/t]

Yes, but that's one of things we consider Proprietary information.... if we gave away all the techniques that we've learned over all these years we wouldn't be able to pay the bills.

Gotcha, did not know you ran a business. That's awesome. I should be able to figure it out no problem. Thanks for all the info guys!

 

[Don Gould]

Ok, well if I have a 12 degree advance canister and my total mechanical is set to 35, then I will be at 47 total timing in theory. I will check it with the light obviously, but I should be ok.

When your cruising you'll have some mechanical and some vacuum so under those conditions you should have 42-48*. At idle with no mechanical and full vacuum you want it at 28-30* this is best done on a distributor machine.

 

[lewtot184]

Ok, well if I have a 12 degree advance canister and my total mechanical is set to 35, then I will be at 47 total timing in theory. I will check it with the light obviously, but I should be ok.

you will have 35 plus 24. the 12 on the arm is distributor degrees so you will be running 59 at full advance.

 

[91r/t]

The arm has 6.5 I believe on it....I will have to check. I meant that number gets doubled. Sorry about that.

 

[91r/t]

When your cruising you'll have some mechanical and some vacuum so under those conditions you should have 42-48*. At idle with no mechanical and full vacuum you want it at 28-30* this is best done on a distributor machine.

I have a timing light with a dial on it. Can't I dial in the timing at idle with the vacuum advance hooked up and the timing light?

 

[65-440]

Whoa, hold on now .. so you also say use full manifold vacuum for the advance can ? I said that and was shot down in another thread on FABO ! It seems most like to use ported vacuum ...

 

[91r/t]

That is what I am going to try and do with my big cam and pig rich idle/kinda glowing headers. Gonna try and add some timing to it with the advance can at idle and see how it reacts.

 

[Don Gould]

I'm not going to get into a discussion on Ported Vs Constant I have explained that no less than 50 times over the years... Ported is for EMISSIONS and CONSTANT is for non-computer controlled engines or Performance. Even Edelbrock has that one figured out finally after 25 years of arguing with them.