ignition timing curve

I would suggest you'd want a curve to allows full advance by ~2500-2700rpm. Good luck..

Bill,

run the black "stop bushing" in the distributor, which limits centifugal advance to only 18 degrees.

Run one heavy silver spring & one light silver spring, which will result in the 18 degrees coming in at 3000 rpm.

Optimize the static (initial) advance setting with the following method: With the engine up to temp and idling, vacuum advance connected normally, slowly turn the distributor in the advance direction (clockwise?). As you turn the distributor, the idle speed should increase, continue to turn the distributor until you just reach the point where the idle speed stops increasing, this is the ideal setting for the distributor at idle. The intake manifold vacuum will be at it's highest point, the exhaust temps will be at their lowest temps, you'll have more low end torque, better drivability, less heat load on the cooling system, and a better idle.

You'll then need to optimize the setting of the idle jets, and re adjust the idle speed with the throttle stop screw.

Your advanced friend on the DTBB, George

George, my Pre-L car has a sticker stating 16* initial (both vacuum lines blocked), is that relatively close to optimium on a stock-ish camed and iron head cleveland?

John,

The short answer to your question is that it is "close" but not enough.

I want to use this opportunity to give a soap box lecture. It's not aimed at you John, so please don't feel singled out.

I have often run into resistance regarding the setting of the "initial advance" on the distributor. People are "afraid" to set it anywhere other than the factory setting, or a setting they read in a magazine, or a setting some mechanic has given them.

I have run into performace engine builders, guys who are intelligent enough to port cylinder heads & grind cams, that have told me " I set all my engines at 12 degrees, it works for me". Crap! LOL.......... These guys accept the fact that engines of different states of tune require different cams, different gearing, different carburetors, different carburetor jetting, even different centrifugal advance calibration, but for some reason know only to them, all engines use the same initial advance setting, doesn't matter if its a Ford or a Chevy, a small block or a big block, an RV cam or a solid lifter cammed dragster. Does that make sense to anybody reading this?

I think the problem is, the best vacuum method of setting the initial advance has never been published in a performance book or magazine. They always give a magic "number". It seems the authors of this literature never ran across the same old coots I did as a youngster. This method for setting initial advance is not my idea, I learned it long ago from old greasy mechanics who learned their trade before Hot Rod magazine existed.

Think of this: "Total advance" can only be determined on a dyno, under load. But no car is under load at idle, so initial advance can easily be determined in the driveway, using the "best vacuum" method I described earlier.

I have never recieved one complaint from anybody, in 35 years, after setting the initial advance as described. It improves every car it is used on. Idle quality, throttle response, acceleration from the stop light, and transition into the higher range are always improved. The auto makers had other problems to deal with (emissions) that prevented them from setting the ignition at the ideal setting.

So long as you do not run your car for a prolonged time in a "pinging" condition, you won't hurt it, so give it a try, experiment. Your motor can use more advance. You will like the results.

I set Dougo's car this way last year, if he reads this, perhaps he can provide a testimonial.

For Ford distributors of that era, connect the outer diaphragm of the vacuum advance to "ported" vacuum, and leave the inner diaphragm disconnected.

My only warning is that your car may not pass emissions testing if it is set this way.

Your friend on the DTBB, George

I completely agree George. I was curious about the 16* sticker as I thought the B2 motor was the only one that used a 16* initial as a factory spec. Thanks

All of the Cobra Jet motors (very late '71 through '74) were spec'd by Ford with 16 degrees static advance.

George

Now that I have this great info. I can't find my spring kit. You know MSD sent it to me free! Looks like I will have to clean up the shop until I find the kit. Thanks george and Johnk.

George is right!.... I bought the MSD "Ready to Run" Dist. coil and the wires. I can't remember what stop I used, but I used a heavy and a light spring. We adjusted the timing by the vacuum gauge. The engine runs great, responsive, pulls great...no pinging, (which I was afraid of).

George,
A well timed lecture as this is on my mind too as I'm planning some rolling road time (I finally found a rolling road guy that's heard of a 'Cleveland'!).
I'm hoping to improve the gas mileage (currently 10 miles per US gallon) by improving the timing and carb set up.

I have, I think, a stock 351-CJ. It has a Mallory Dual Point set to 10 degrees advance.

Sounds like some more advance would improve things but what about the maximum advance? At the moment I think I have 26 (may be 28) to give 36 (or 38) total advance.

Any idea of a reasonable setting for static and maximum advance?

Also I have the choice of 94 or 91 octane (US PON) fuel here - is it reasonable to expect to run on the 91 octane with this engine?

BTW - Your method for setting the timing is the same one described in the official factory workshop manual for the Hillman Hunter/Sunbeam Arrow/Rapier cars.

Derek,

You should be able to run the lower octane fuel with no problem. To experiment, run the tank almost empty, fill it with 5 gallons of the low octane stuff & give the car a drive. If it pings, you still have room in the tank to add enough high octane fuel to dilute the lower octane stuff.

The "generic" total advance number always given for the 351C is 36 degrees. Total is initial advance plus centrifugal. If you arrived at 20 degrees initial advance using the method I described previously, you would therefore need 16 degrees centrifugal advance (20 + 16 = 36).

The truth is your Cobra Jet motor with open chamber heads can probably use more than 36 degrees total advance. BUT, nobody can give you the proper number for your car without testing it on a dyno, the needs of your motor are highly dependent upon a myriad of factors including the octane of your fuel, the design of the cylinder heads, the specs of the camshaft, the design of the intake & exhaust systems, the calibration of the carburetor, etc..

There is an "on road" method to determine what the best total advance for your car is, but you need a lot of open road where you can drive fast. The best total advance setting will allow you car to pull higher rpm when wound out in the higher gears. The Pantera can go pretty fast in 5th at red line!

One last thing, the calibration of the timing marks on the harmonic balancer ARE NOT accurate, I guarantee it.

Your friend on the DTBB, George

George,
The dyno is the plan.
I just have to decide whether to get the motor set up on a tank full of the ordinary fuel or the higher octane stuff.

Do you think having the motor set up for the higher octane fuel would give a noticeable improvement in power or gas mileage?

I have seen the tacho reach the red line in top gear (once) - but then the tacho is probably about as accurate as the speedo (i.e. not very)

Derek, since the motor is a relatively low compression motor (8.8:1), I don't believe tuning for the higher octane will achieve anything.

your friend on the DTBB, George