I have several questions about terms that have come up on occasion.

Number 1: What is Port vacuum, timed vacuum, other vacuum, etc. What is the difference and how does that relate to where you use it and find ports under the hood.

Number 2: I have a vacuum advance on the dizzy, right? How do I know if that is working?

Number 3: Can I get a picture of where to attach the electric choke for power? not the end on the carb, the other end.

Number 4: What method is used for removing the chrome trim from the truck? Do I just use a pry bar and crank on it or is there a better way?

Number 5: I guess thats it for now.

 

1. do a search on google!

2. Yes, if you have a timing light you can plug and unplug the hose but you need to increase the engine rpm. There should be no adavance at idle with ported. Or remove the cannister and push in on plunger, place finger on spout and release. You will be able to tell.

3. I am not an electric guru but a 12volt power source and a ground should do it.

 

When I search google, it says, " Hey stupid, ask someone at FTE?"

 

Some people aren't resourcful.

Manifold vacuum is selected from the intake or base of a carb. It pulls a lot of vacuum at idle and low rpm. The amount of advance decreases as the throttle is opened. Its an old school way of doing things. Ported or timed is above the carb venturi's and has no vacuum at idle till around 850rpm. As the throttle is increased so is the amount of advance until near WOT. There is NO vacuum advance at wot to speak of. Ported is commonly used the last 30 years or so. It is more emission oriented but has increased gas mileage and part throttle respnse.

It is most likely the way to go. The main thing is to make sure your inital and centrifugal are able to cope with the vacuum advance so pinging does not happen. EVERY duraspark FE dizzy i have seen has a 16L weight and has 32 degrees of timing be itself at around 4000 rpm. This is to much!!!!!!!

 

"make sure your inital and centrifugal are able to cope" What does this mean?

"16L weight and has 32 degrees of timing be itself at around 4000 rpm" I don't understand.

Sorry!!!! I can be resourceful, that is why I am using a forum that is dedicated to my vehicle. I have seen you be very helpful to others, perhaps you are having a bad day, or I am misunderstanding your tone.

 

OK, there is 3 phases so to speak. Inital is what your balancer says and it is what is set via basic timing light. Typically 6-14 btdc and the goal is to build peak cylinder pressure and then ignite. As rpm increases you need to fire the plug to compensate for the increased speed of the piston.

Inside the dizzy is a piece that has 2 weights,and a tab and comes in the following combos 10L/15L, 13L/18L, 16L/21L etc... The tab that is hooked up is the amount of centrifugal or mechanical advance. For instantance 16L would equal 32 degrees. This is because the cam turns at 1/2 the speed of the crankshaft. So the readings are doubled. Mechanical advance is the 2nd phase of the timing. AS rpm increases the amount of mechanical will increase. This is controlled by the tension of the springs inside the dizzy. A lighter spring will let the timing come in sooner than a heavier spring. EX. a light spring may let full advance it at 2800rpm while a heavier spring may be 3700rpm. Mechanical is added to inital so if you had your timing set to 10 dgrees. You would have 42 total.

A race setup would be something like 16-18 inital with16-18 mechanical in by 2500rpm or so fot a total of 32-36 depending on situation. NO VACUUM ADVANCE!!!

Now for the 3rd phase is vacuum advance. Like I mentioned earlier it adds advance to the motor. Say we have 10 inital again and are 16L tab, you know you have 42 total already and 36-40 is ideal for iron headed motors.

Lets say the motor is idling in the driveway at 700 rpm. So right now we have 10 before top dead center firing. AS you go to drive down the road, the throttle is opened and vacuum advance will add timing, for examples sake 17 degrees at 1500 rpm. Now as you increase your speed, the amount of vacuum advance and mechanical will increase and that is added to the starting 10 btdc. Lets say you cruise up to 2200rpm the vacuum and mechanical will increase some more so for ex. 34 btdc. So as you are going down the road the engine is firing at 34 degrees btdc. Lets say you step on it and you are at 3000rpm. Well, we got more rpm so more advance well lets say we are pulling 48 degrees btdc. Now this will or may cause the engine to "ping" denotate. Meaning the air fuel is ignited and the force slams the piston back down as it trying to come up. This causes damage. Can be very severe. Well then continuing, lets say you see a chevy 1500 and mash the pedal to pass him. So, your ar at WOT, so the vacuum advance is no longer an issue. You have you starting 10, plus the 32 at 4000-4500 rpm for a toal of 42 btdc. This is less than the previous 48 is easier on the engine.

The problems arises at part throttle conditions because the vacuum is strong and the engine doesnot need to be fired that soon. For ex. you are at 2300 rpm, you have 10 inital, are pulling 20 degrees from vacuum adavnce, and have 14 from mechical. So that is 44btdc at 2300 ouch!!!! the engine doesn't need to fire that soon and its causes the preignition, ping, etc. If we can run at 4500 rpm with 42 btdc why the hell would we need 44btdc at 2300. We don't, it causes problems.

So, we tweak the igniton to say 6 inital, use a 10L tab, use and adjustable vacuum cannister(the piece to the dizzy). So with this combo we have a very conservative 26 total. But at say 2300 rpm we might have 6 +14+10 for 30 degrees btdc at 2300 which is much better than the previious 44 btdc. Which is less prone to preignition,ping, etc...


I hope this helps a little.

 

Wow, that was fantastic. I guess I never thought about timing during acceleration. Now if we use manifold vacuum, we would lose the vacuum advance as we accelerate rather than gaining advance, right? So we use ported or timed advance to keep the advance ahead of the piston just the right amount.

 

Or use the search on FTE. It's the third button from the right (Log Out is the first). Good explanation Matt, do your fingers hurt? LOL

My books only cover '70 to '79, but the electric choke on these connects to the Stator terminal on the back of the Alternator. Since these windings are center tapped (except the 70 amp), stock output at this terminal would be 7.5V. I guess the thing to do is determine the voltage rating of the choke, and output at the stator terminal: they need to match.

 

You got it!

 

Hypoid, my fingers don't hurt but i tried to avoid rambling on by having fly do a search. As long as it helps someone I guess.

 

Thanks again!!!!!!

 

LMAO! I'm trying to put my-self on a word budget, had to ask. I have to say that using the search here and at Net54 has answered questions I never knew to ask!