FBO springs

cuda66273 · Nov 13, 2017

70 DUSTER CRATE said: ↑
Totally agree !
Hey it's a learning process. You have to try things and see what works. I'm still learning. Here's My 2 Cents.

IMHO, Before you get to the springs,
if you had your dist. set up by him, take the initial timing spec. and the vacuum timing spec. that he gave you, and add them together.

Initial timing is always set with NO Vac Connected, the idle timing (initial) plus the Mechanical timing will give you your total UNDER LOAD. When the engine is under load there is no manifold vacuum so there is no Vacuum timing.

Performance engines should always be Power Timed with a dial back timing light the total timing is the most critical. Set the light at 34* then bring the RPM up to just above the all in number your looking for and set the distributor timing to read "Zero" where it falls down to is what you have for Idle timing. If your using our plate it should be dead on, if not then you need to double check to be sure the RPM was high enough to fully advance the weights.

Set your initial there.
See if your starter kicks back, just like the book says and it's what Crackedback always says to do.
I don't know what motor you have for a total? But Don't drive your car until you Reset your mechanical, using your plate. Take your initial plus the mechanical you set it to, to get a total. A total for a 340 is near 35 degrees. Say 35 - [12 + 12] = 11 degrees mechanical.
Hook up the dist. to ported vacuum, forget the manifold vacuum just plug the port on your carb., and use your allen wrench adjustment, [in the vac can] for when it is to come in, [ at what vacuum]. Test, it should be about 50 degrees of timing with the vac can, for your Grand Total. Still thinking for a 340.

You need to understand how Ported Vacuum works....
As the airspeed or air velocity increases through the Venturi it creates high pressure in the center (which explodes the fuel into small particles) and the equal and opposite reaction is Negative wall pressure. This is the source of Vacuum for your vacuum advance so the higher you spin the motor (velocity) the more vacuum is produced and more timing is pulled into the motor. This is exactly what you don't want, so if you have a vac can that has say 20* of stroke in it you will have 34* mechanical and another 20* vac for a total of 54* and good bye crank shaft and pistons. When we curve a distributor we have ways of limiting the stroke of the Vac Can to get to where we want it when Connected to CONSTANT Vacuum.
You might be able to get way with this if your using an old antiquated transistor box like an Orange box or some Chinese stock type box as they all retard the timing under load by at least 8* ... strange way to try and get your tune-up right.

Ported vacuum is for OBD1 and newer vehicles with computer controlled timing retard dictated by a cluster of probably at least a dozen sensors ( I believe a Viper has 16, O2 sensors alone) Timing controllers can only retard timing they only pull it back from the total allowable timing set in the timing MAP.

So now you connect it to Constant vacuum..... At Idle and part throttle you have vacuum timing which is responding to the high HG's of manifold vacuum. So when the engine has no load or very light load (cruise) you have high vacuum which advances the timing and under load releases the Vac timing to match the load being applied and the springs take over. This is a very simple design that has worked since the late 50's I believe our friends over at GM figured this all out and all GM performance distributors were always connected to MANIFOLD vacuum, until the curse of emissions controls in the mid 80's.

Why so much Idle timing? At Idle or Part Throttle cruise you are trying to burn a very lean mixture. A lean mixture takes longer to burn than a rich mixture, the particles are further apart so it takes longed for the flame front to propagate and go into the expansion mode, you need the piston to be at about 13* ATDC to apply pressure to the crank turn it (tork)
New cars run around 40-50* of idle and cruise timing because they run so lean to achieve mileage numbers.

My experience with Don was good. When you are done doing it his way, you know a lot more about your ignition system. The white control box, that I bought from him is very good, although if you have a plain stock coil, you probably don't need his.

Using any other coil than the one that we have set the computer chip dwell to recharge and you will overheat the coil and it will probably fail. Or it will not accept the short dwell time and drop the output capabilities of the system. When we did our research on coils we tested over 100 coils and the Pertronix 40011 met the rigid standards demanded.... Availability, Durability, Capability and lastly Price. We then set programed and burned the Intel chip to maximize the system as a whole. You don't have to buy our coil but using anything other than the 40011 PTX coil will not optimize you system (Capability). To date and over 4,000 units in service we have had 2 Coil failures (Durability) and you can buy a 40011 from any mail order house or major Auto Parts store throughout the USA (Availability) Our Price on the coil is $30.00 when included in the kit you have the part number go check it at Jeg's (Same Price). Our Price on the kit is also "Free Shipping"

The 2 coils we had a warranty claim on were replaced same day shipping paid and we relied on the integrity of our customers to return the defective parts.

I have the book and if you are a beginner, it does help you set your basic idle settings. The T-slot, which is what AJ pushes , is the Big key for tuning you carb. Set your idle screw and don't touch it again. Use the secondary screw.

More initial at idle will give you a cooler running motor and the RPM'S.
And why is that???
If you don't have enough initial timing in the motor it won't have time to burn the fuel before it gets to that 13* magic number so it can turn the crank. So if your expansion mode in the combustion chamber is late then the pressure is just chasing the piston down in the hole and because your not keeping the fuel pressurized your not burning it all. So now the piston is coming back up and pushing that smoldering fuel out the exhaust port where it reignites and creates a blow torch in the head runner and cooling system just can't keep up. Also results in poor throttle response, stinking rich idle, stumble and hesitation. Also leaving serious carbon deposits on the back of exhaust valves, exhaust ports, on the piston choking up the rings and eating your cylinder walls up. So even if YOU think it's running fine with 10* of idle timing it's not happy and down the road it will tell you.

Just toss out the , using Manifold vacuum for your dist and using too low of an initial.
And now you have Vacuum Advance at cruise. The way it was supposed to be.
Now you're on your way, and now you can experiment with the springs.
Like I said, Just my 2 cents. I hope I got it right ! LOL.
And watch out for the salesman, he'll sell you the whole store.
Hope this helps !
Click to expand...

So Ported or Constant?
now you know how they work, you can now make the right choice.

Where to set your initial, total and Vacuum timing? When you purchase our products we're always here to guide you, it's included in the price.
Don't do HALF the job if you want it to live and perform like it's capable of don't think that just the timing plate or just the Ignition Box will do it all, do the whole job and enjoy the power of your Mighty Mopar for years to came.

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