Thanks, I believe that's the procedure I was looking for. Anybody got any numbers I should shoot for?

 

If it's a street motor I wouldn't get to carried away with quick advance or total timing (can cause heating problems or even knock holes in your pistons). If you plan on towing at all, say 34° total in by 3500 RPM. No towing in an F150, then 38° total and in by 3000 RPM, but make sure it ain't pinging this far advanced (back in the old days of real gas, both cheap and high octane, it was no problem but now, who knows with out testing).

 

OK, I think I get it. Do these rpms work w/o a load. Just rev her up and watch the timing marks?

 

OK, I think I get it. Do these rpms work w/o a load. Just rev her up and watch the timing marks? of course I'll have to see what it does under load, If she still pings start retarding again.

 

The mechanical advance works off engine RPM only and is the same loaded or unloaded. Vacuum advance varies depending on load, because the vacuum changes with load. And of course, like you said, the real world over rides theory and if it pings, back off on the timing.

The way I like to determine initial advance is find out what the total is and then check the intitial and I mark it on the damper. Then I know where to set the initial to and not have to rely on counting those little marks (and they get littler every year) from zero everytime.

 

I don't understand initial and total? Can't quite picture the procedure your talking about.

 

Since most gas these days is un leaded the factory timing specs can get you in trouble. By setting timing at max, rev'd up, you have also established initial for the existing dist curve. Mark it for future reference. If you set initial and "hope" about the max, it's a crap shoot as to the pinging and detonation. It is becoming more and more popular to set the full, and let the initial fall where it will. To do this you could/should use a dial back timing light. They are very handy, being able to dial the advance back to timing mark zero, then just look at the dial to see how much true advance you had. It is really tough to set the max this way without one unless the balancer is degreed up to the max desired advance..............aMP

PS: The initial is where you set it at idle. The total is the amount of advance in the distributor, be it mechanical or vacuum, PLUS the initial setting. ie, 10 degrees initial, 14 degrees in the advance system = 24 total degrees of advance. OK, you want 28 degrees total, rev it up, set it at 28 total, and when it comes to an idle, the initial would be at 14. Without some serious, precise examination you'll never know the total, just the initial and how it feels in the seat of your pants. A carefully curved distributor will make a lot of difference in performance. Regardless of the vehicles usage, most can be helped by some massaging in the distributor curve area, remember, effiecency is economy, as well as performance.........aMP

 

aMoneypit; from three of your replies, #5 and #11 "tweeking of the mechanical spring anchor to limit max advance". Spring anchor increases or decreases spring tension for the mechanical to come in at a lower or higher rpm, the advance limit is controlled by the slot you use (two to pick) plus the different wall thickness of tube slipped over the post inside that slot should you take the time and fine tune.

Again at reply #22, "setting timing at max.rev'd up,you established initial". WTF is that? Know how the motor is going to be used, empty or loaded, gearing, your maximum initial, maximum total and set the dizzy within these limits, adjust when you want mechanical and vacuum to come in. To have a dizzy spun on a machine is a general ballpark and no two motors are alike even if built to the same specs. It takes days to fine tune ignition timing with a lot of notes to do it correctly unless just runs is your idea of good enough.
Please don't give bad advice for others who don't know and screw them up.
Doesn't anyone listen to Bear 45/70, he said everything but a hands on set up?
As far as a DuraSpark dizzy with the componet failures they have I would run one only after installing GM components in it. Not brand bashing, just run what works.
.....=o&o>.....

 

So go back to my Points Dizzy and tell Crane to stick that XRi contraption ?

 

You talking to me?
I've never had a problem with Crane ignitions be it a Allison (Crane purchased them years ago), a Crane XR700 (just a renamed Allison that still needs a resistor wire or ballast resistor). Now a XR3000 that has no resistor wire or ballast resistor to limit primary current hence higher secondary current with their LX-91 E-coil.
The XRI is current limited, has a rev limiter a plus to some but I use a tach as the truck is a daily driver not a drag truck.
Better to buy good once than many upgrade steps later as this isn' cheaper in the long run.

.....=o&o>.....

 

Initial advance is what the factory gives you in the tune up specs. Usually 6° to 12°. If you recurve your dist., you change the advance curve and usually change the mechanical advance total, which by the way is normally called total advance. Vacuum is not included in it as there is very low vacuum at Wide Open Throttle (WOT) and at less than that you can normally run extra advance which is what the vacuum unit does. When I recurved my last dist., a Dura-Spark on my '84 460 in a F-250 SuperCab, I changed the advance curve from 36° in at 4600 RPMs (plus the 6° initial for a total of 42° at 4600 RPMs which the stock exhaust would barely let the motor reach) to 26° in at 3500 RPMs. The stock initial was 6°, but with the shorter total advance curve I ended up resetting it to 8°. So 8° initial plus 26° I have a total of 34° at 3500 RPM (vacuum does not count here as it works only when the load is light, a gas mileage boost system which at WOT there isn't any such thing). I tried running 12° initial to start but I had a slow overheat problem with the camper (3800 lbs) on board and the quad trailer in tow with the quads on board. Didn't have it with the factory set up so I backed off 2° and it helped but didn't completely cure it, hence the 8° number. The dist. recurve netted me a 1 mpg increase with the big load and a 1 1/2 mpg without. I've recurved many dist. in FE engines over the years, the last on a 390 I built for my '68 F250 with GT heads, manifold and carb plus an RV (read low duration and high lift) cam. The truck got a best of 13 mpg at 55 mph empty and 9 1/2 mpg loaded.

 

OK, I'm getting a picture. I may have to have my laptop sitting on the fender as I rip and tear. I'm stil not sure of what I'm looking for (Doing) under the under the plate. Maybe the link given earlier will guide me after I get things coming appart? Thanks!

 

The link will even guide you thru getting the plate off. It has good pictures too. I don't recommend pulling the dist. out of the motor unless you can do the replacing the dist. in the motor thing quick and easy. If you change timing advance slots you will have moved the firing order 180 degrees. Rather than screw around with pulling and reinstalling the dist. with the rotor moved 180°, I just move the plug wires. A whole lot less stressful and the motor doesn't care where you start #1 wire on the dist. cap.

 

"Aaaaaa!" -scared Beavis&Butthead sound

Truer words were never said.

I'm not here to pick on you, moneypit, just to reassure you that what Bear 45/70 said in post #6 is right on the money. No kidding.

It's very condensed information but right on the money, ok?

I was an old air cooled VW guy and all you can buy are mechanical advance distributors for those things (if looking for "new"). The only way I found to get one that has both systems, is the get a "rebuilt" (yeah right, cleaned more like it) from AutoZone etc.

You'd just have to experience the difference yourself to believe the crazy sounding claims by those that have experienced the difference. Disconnect your vacuum advance and drive down the freeway?

The "re-incarnation-automotive" website is a real-good-one but doesn't address the centrifical + vacuum advance issue at all (that I saw) and that is soooo-typical, it ain't funny. :/ (I wrote down that table to save in my service manual, something that should have been in the Ford service manual to begin with IMSorryO)

My stock dura-spark system, '75 F150 360 T-18 while settin' in the drive way and reved up with both tach and timing light going, will advance about 60 degrees -total-. Yep, that takes some funny, never read anywhere before, engineering to figure that. (I'll scan a picture and post it for you)

Alvin in AZ

 

Alvin, you rag on me about a quick and easy way to limit the mechanical advance, and then you say that 50 degrees in a 70 390 is OK, then you say you're getting 60!!!! Get a grip man, 50 degrees in that 390 will hammer all the wrist pins out of it, if it doesn't just burn right through the pistons. The highest of high performance endurance racing motors might see 42 to 45, locked out, with 110 minunum octane or higher. Put 50 degrees total in that 390 and you'll be walking home. As far as what he said being right on, where did I say anything that wasn't? My 68 f250 with basic 428 would ping like crazy with anything more than 2-4 initial, which made it a turd, I bent the spring anchors to limit the mechanical advance, set the initial to 8 and every cylinder is happy. BTW I get 13 TOWING w/ a Carter 600, and the jets swapped, pri/sec, just swapped. All I said was to set the max, and let the initial fall were it will. That is simple for someone that hasn't a clue about curving a dist. I also said that this is a base line, and if it pings back it off until it doesn't, but that is where the bending of the spring anchors comes in. And that is where this whole deal started. Consider this, 13.5:1, 113 octane, 38* locked out, 7750 for 5 miles of racing, on the water. I don't know what I'm talking about, but we were 1 in the western division, and number 2 in the USA in 2004. Why would you ever need 60* of timing in a 360 that never sees 6K??????......aMP