I've been doing some tweaking on my engine trying to get the best tune possible. I found something in my research that suggested no more than 35° total timing for our engines. I was wondering what you guys were setting your total timing at? For a mild street engine would this be the optimum ? Just curious.

Durham Missouri

Yes that's about right [but like all engines it might vary a little] Of course listen for detonation on load to confirm. Now you need to modify your dissy to get about 12 degrees at idle, do a search about the mods ..  ; )



"Came too close to dying to stop living now!"

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42-44 Total is  a good Guideline. Initial+ Vacuum+ Centrifugal. All in by about 2500 RPM. Vacuum Advance comes back in when Engine Vacuum is high at Cruising Speed..Greenbird56 Steve Metzger had a lot of useful Information about Timing and setting up Stock Ford 57+ Distributors if You can find some of His previous Posts.

  

Thanks. I've had mine as high as 39° but it detonated under load. Right now it's at 35° but is a little bit of a slug at low rpm. I was messing with the initial trying to get it to clean up at idle. I had it up to 25° base with a 10° advance bushing for a total of 35 then I hooked up the vac advance to the constant and ported with no change.

Durham Missouri

That's a good point Mark said its more with vacuum connected .. cruise.  But do that last.



"Came too close to dying to stop living now!"

My motors have seemed to like about 10-12 initial, and around 35 total, in by 2500-2800rpm. You can run another 10-15 of vacuum advance, but that depends on when it comes in. With a lot of lead, I’ve have 1/2 or 2/3 throttle pinging that doesn’t happpen at full throttle. Too much vacuum advance at too little vacuum. Some cans are adjustable for total, but I don’t know of one for our motors adjustable for both total and vacuum. Compression ratio, fuel quality, and temperature all play into this at the edge. I don’t race, so I tend to back off and be a little conservative. One of my blower motors used a retard module that activated at 2lbs for 2 degrees.

miker
55 bird, 32 cabrio F code
Kent, WA
Tucson, AZ

This Information is for the Conventional Distributors like the Cardone 30-2808 Ones. The amount of Centrifugal Advance is controlled by the "Slots" in the Cam Plate.  Ford Distributors usually have 2 different Advance Options on that Plate. Identified by 13L or 10L marked on the Plate. There are some that have different Advance Slots but 13L and 10L are most Common. The #'s refer to how far the Cam will Advance and converted to Degrees at the Crank Damper are 20 and 26 Degrees Advance.You can change the maximum  Amount of Centrifugal Advance by switching  Cam Plate so that either the 13L or 10L Slot contacts the Stop limiting the amount of Advance. You can also customize the amount of Advance by reworking the Length of the Slot to either longer giving more Advance or shorter for less. How quickly the Timing Advances is changeable using lighter Springs like the 925D Kit from Mr. Gasket.  The Vacuum Can can be Adjusted using an Allen Key through the end of the Can where the Vacuum Line goes on. Turning CC limits the amount of Advance and clockwise allows more. The older Distributors using Springs and Spacers in the Vacuum Advance are adjustable by changing the Spacers. The newer Allen Key type are much easier to adjust. If Steve Metzger reads this Post hopefully He will add his Expertise to this Post with Diagrams etc. On mine I have 10 initial + 26 Centifugal + 6 Vacuuum= 42 Total.

  

I'm running an MSD dizzy. Right now I have the mechanical locked at 10° and base set at 25° with vac hooked up to manifold vacuum. I have several different size bushings to play with. I'm going to try a 14° with 21° base next. I had read once that my total should be at 38° but that seemed a little on the high side to me.

Durham Missouri

There are so many variables involved to add to the confusion. Elevation, fuel quality, compression ratio, gearing etc. Internet discussion forums have a tendency to magnify misconceptions back and forth, they get repeated and exagerated with each retelling and over time take on a life of their own, to the point that often something that "everybody knows" - just ain't even so in the first place!

One of the first steps to good tuning is to make certain that the TDC indication - upon which everything is based - on the damper aka harmonic balancer is 100% accurate. This cannot be overemphasized. OEM balancers are (by now) always in need of replacement or rebuilding. The steel outer inertia weight is sandwiched to the basket with elastomeric (rubber compound) over many years it "dry rots" and the balancer no longer performs a very important function. On top of that, though the weight will slip off its clock or index, and along with that the damper timing marks will be several degrees off. Keep in mind it only takes an adjustment about the width of a pencil line at the distributor to equal 2° timing on the damper. If the damper is defective the actual timing may be off 10° or 20° compared with the marks on the damper.

Then there's the problem of terminology. When you hear someone talk about "total" timing advance, and the numbers, they often include the vacuum advance on top of the mechanical advance. This is incorrect. Adding to that is a serious misunderstanding of vacuum advance, how it works, and what is its function. The bottom line is you have to be willing to experiment and determine what works for YOUR engine, each engine is a bit different. Don't worry about what "seems" too much, find out for yourself - get in the manual. And while each engine is different this is well travelled ground and some general numbers have been published. Get in the manual and look at the specs that Ford came up with. Disconnect and plug the vacuum advance, perform all tuning and adjustments with this in mind. When you are satisfied with the way it runs without vacuum advance connected then it's time to dial in the vacuum advance. Remember distributor degrees are published at "half" the numbers found at the damper. Consequently when we see 13 or 18 advance limit degrees published in the manual it translates to 26 or 36 crankshaft degrees. PLUS, whatever initial or base timing is at. This is the "total" timing BTDC at which the mechanical distributor is done advancing. The RPM at which this point is reached is governed by springs securing the centrifugal weights. You absolutely must know this number in order to properly tune the engine, it is more important than the number of degrees initially set at the distributor. The only way to know is to run it up with a timing light and see what it tops out at.

Another bit of confusion as mentioned earlier, Vacuum advance only provides additional timing under very specific engine conditions - it is strictly load based whereas distributor advance is based on RPM. The two systems work hand in hand and complement each other, but are completely independent. When cruising at a steady speed on level ground for example, the engine load will be very low, and engine vacuum very high. Air Fuel mixtures are relatively lean, and needs the fire lit earlier - more advance is needed. Engine RPM on the other hand, will be relatively low in high gear. Vacuum advance takes advantage of these characteristics and provides more advance than the mechanical arrangement alone can provide. The stock, OEM advance is somewhere around 50° BTDC under these specific conditions! Don't believe me? Look it up. It's all there in black and white.

I went total advance with vacuum somewhere over 50 when I was messing with EFI with stock '59 engine years ago.
I leaned engine low as possible but didnt get more MPG' s.


Hyvinkää, FI