So that's 28 degrees advanced with no vacuum at what rpm, unloaded i m guessing? I've been setting my initial at about one thousand RPM, I run premium in it and and got a Holley 4-barrel with an offenhauser intake and dual exhaust headers, I know when I first put the distributor in my initial was about 50 degrees and there was no ping at idle surprisingly.

 

Yep disconnect and plug vac advance. If you set initial timing at anything above idle, the weights start to move and it will skew the results. Set the initial at about 550. Sloooow... Then we KNOW our initial timing adjustments are accurate. Set it back where you want to later, if it's too low.

But again the initial timing number doesn't really matter all that much, set it wherever it needs to fall, to get 28° BTDC at 3000 or 4000 RPM on the far end. Normally most people want a little more zip and install lighter springs, and the timing will hit 28° before 3000. We won't get into that, the point is you want to verify/adjust at what number the mechanical advance stops at. If it's 30° or 32° where you start hitting engine knock that's fine, if it's 27° that's OK too. The only way to do that, to find out where it needs to be is to spool up the RPMs in neutral till it stops advancing, test drive it and check for ping. Depending on compression ratio, elevation, fuel quality intended usage, you can utilize more or less ignition advance than the stock OEM or what the book says. Experiment.

You're tuning an engine, not a book. Ignore them especially if it runs better your way It will get you pretty close, but it's up to you to dial it in.

Try setting the initial to 6° and spool it up in neutral, be careful - mind the radiator fan and belts &c. Stay out of the plane of the fan. Myself I don't like being around it when spooled up like that, but it's the only way, unless you have a distributor machine.


Normally an engine will never crank, or super slow maybe with around or approaching 20° initial. Starter kickback. Worse when engine is hot.

Can run lots of advance at idle because no load = no ping. Lots of guys will run straight manifold vacuum to distributor, no ping, lots of advance (maybe 30° +) It will run a lot cooler.

 

As Ted stated 100 RPM is too high you need be under 800 RPM you may ... well should be getting some advance at 1000 RPM. Since you obviously have a performance build, the book its of no use to you other than a starting point.

Ideally you should want your total around 32-38° depending on what your engine can take with out pinging. As a general rule, the lower the compression of the engine, the more timing the engine will want at any given rpm. Conversely, higher compression engines usually require less timing. You want total total advance in by 2500 RPM or so

If you engine is stock compression ratio start at 38°

Your total is set with the vac-advance disconnected.

Is trial and error with test drives. If you have pinging back of 1 Degree and test drive. keep do till you have no pinging then back off one more 1° this gives you a of bit cushion.
If you have no pinging advance till you do get pinging then back off 2 °

if you end up with stupid initial advance any thing over 15 or 16° then you will need to change the reluctor in the Dist to give you a larger amount of total advance.
This will push your initial back down.

Example you end up with 38° totoal advance and have 18° to play with. That puts you initial at 20° well that just wont work.
18° of advance means you have a 9L reluctor in play. All ford reluctors have 2 sides one small one large. Ok so lets say the other side is a 15L that would give you 30° of advance. If you remove the reluctor and flip it around that will give you 30° to play with, knowing you want 38° total and you have 30° of advance that will put your base timing at 8° a nice easy to engine start number.

Once you have set your total you can adjust the vac advance.

Same procedure test drive, if you have pinging back off the vac advance 1/4 turn.
When you have no pinging back another 1/4 to give you some cushion.

 

So I set it to about 8/9° @ 550 rpm and it hits 28° at 3000rpm no vacuum, but when I hook up the vacuum and it idles all is good, but if I open it up say 200 rpm it starts to misfire a lot and studders till I open it up more (I'm guessing taking away the vacuum??? And I took off my vacuum cell and looked all over and inside and there is no adjustment screw at all.

 

OK, Mathew is saying (I think) 32° to 38° BTDC is OK for your Six. That's what you want to do then.

It would be unusual (but not unheard of) for vacuum advance can to be non-adjustable. Have to go dig around the GM sites for your HEI I guess. It sort of sounds like a vacuum leak though.

When you rev it up without the vac advance it should advance smoothly up and back down without scatter or fuzziness on the damper.

Then, when you re-connect the vacuum advance and rev it up it should do exactly the same thing, except now it's going to go a lot farther. Probably around 40° BTDC, more, especially if you goose the mechanical to 32° or 38°, most OEM engines cruise on level highway around 50° to 52° BTDC; sounds crazy but it's true. If it doesn't - if it tops out at the mechanical limit with vac connected that points to defective vacuum can introducing a major leak.

But remember CropDuster was talking about advance plate strangeness or somesuch earlier in one of the first posts. Engine popping when vacuum advance is re-connected can be a vacuum leak. But, if that isn't the case here it must be something is defective internally like he's talking about.

 

Not all vac advance units are adjustable the factor ones are not for the most part almost all after market ones are, IIRC it is a 7/32 Allan key that is used to adjust them.

Crane sells a nice kit for rec-urving and adjusting your total and vac advance.
https://www.summitracing.com/int/par...view/make/ford

And do not use manifold vac for your vac advance while tuning use the ported one on the carb. Once you have it set you can then try manifold and fine that but do not start with it.
And really 28° is leaving crap loads of performance and economy off the table if you are running an 8:1 ratio.

GM dist but same idea.

 

To save me from typing a book and taking a bunch of pictures I did a google search and found this. This is exactly what I've been doing to the Durasparks for years now. Same principle on your distributor except you may have to slot the holes in the rotor button and move it, if it is off. But again a timing light and a hole in the cap is the only way to know if the phasing is off. Junk Yard Genius.com Rotor Phasing For Motorcraft Distributors Page
As far as adjustable advance canisters go, the only thing you can adjust is amount of vacuum it takes to pull in all the advance that the canister is capable of. If you have a 10 degree can it's always going to pull in 10 degrees at the distributor, "20 crankshaft degrees". The only thing you can change is the amount of vacuum it takes to make it do that. For Durasparks, something I know about, you can buy vacuum cans that pull in different amounts of advance, 4,8,10, 12 camshaft degrees etc. then adjust them to pull that amount in at the best time for your engine combination. And that requires a lot of driving around with a vacuum gauge on the engine and listing for pinging or noticing if it's surging.
A couple of questions. Did you run this engine the way it is now with the old distributor? And along with this 4 barrel carb and exhaust did you change the cam?

 

Yes it ran good before with a stock distributor with a pertronix pickup and coil, the only reason I changed it to a new distributor was because my bushings wore out and the shaft would wobble at random times and open and close my points irregular which was a fun thing to figure out, hence the electronic pickup, and at that point I was like get that damn thing out of here and and I had heard good things about HEI so for about the same price I figured why not, but after this experience I'm thinking I will get a new stock distributor and put the electronic pick up in it and get that setup and hopefully have much better luck.

 

That sounds like a plan. You can send your distributor off and have it rebuilt, or try looking on e-bay for an NOS Motorcraft. I've found some pretty good deals on there before. In fact the Duraspark that's on my truck came from e-bay brand new in the box $75 with free shipping. Of course I had to re-curve it but that's not difficult just time consuming.

 

Ran across this on e-bay. It is a deal for sure if it will work for you. You might have to re-curve it, since you have more carb and better exhaust than stock. And of course you would have to wire it up to a Duraspark or a Mopar ECU to use it. I personally prefer the Mopars.
https://www.ebay.com/itm/NOS-NIB-DA-...53.m1438.l2649