So, I have a Progression Distributor which is a timing table based electronic distributor. No vacuum module and no mechanical weights....its all electronic.

It has a vacuum based sensor that I hook to full manifold vacuum and that is used in the load vs rpm table to target any timing advance I want.


SOOOO,
Given my system on a stock 400 with lots of miles what would you all suggest for ignition timing.

I have locked it out (set all values in table) to 32 and motor starts and runs fine. I can watch the cursor move between load/rpm locations and all is fine.
I have set idle timing to 36 degrees, and it starts hot fine.
I have set idle timing to less than 16 degrees and engine seems to struggle.

Highest idle at 32 degrees but only by 50 rpm or so different than 24 degree BTDC.

I have run at cruise between 28 and 38 degrees.....seems to like the 30's best.

WOT is difficult. Most tables go to 100 kPa but I live at 7800 ft and cannot get above 80 Kpa due to thin air. So it hit 48 degrees of timing at wot with no pinging, I think this is due to low dynamic at my altitude.

SO, my question is what timing should I input at idle in park, what timing should I input for timing at idle in gear, what timing should I input for cruise, and what timing should I input for wot?

Its almost infantilely adjustable so give me your best thoughts and I will try them out.

 

You have big numbers there
Usually you are not to exceed 38 total advance
Initial at 6 (or 10 - 14 for your altitude) I used 20 initial on my 302 Chev at 5000 feet
Let the curve go to 38 max and retry it
Go easy, those 400s like to ping
Use a digital light with a **** so you know where you are at
Do that to to double check your curve

 

Do you know how much vac adv there is at idle (manifold vacuum) ?

Using 20* as an example, when you set your timing at 16*, was that inclusive of vac adv ?
If yes, 16* (above) less 20* = 4* retarded, and that's why it would struggle.

Is the 36* above = 20* advance and 16* mechanical ?

Whatever your answers are, and as you've confirmed already, you can easily run numbers as high as the engine will tolerate without detonation.

Test drive, adjust, test drive, adjust, until you get the best feeling.

(I ran 20* vac adv + 20* mechanical (so total = 40*) at 800rpm idle (auto transmission) at sea level without any issues.)

I'd expect your cruise timing to be higher (40's to 50's), but again, you can dial it all in to get the best feel (and gas mileage).

Double check that the mechanical curve is linear.

Did you ever choose and fit a new cam ?

 

Since those dizzys are totally electronic you can do whatever feels the best for you. They have automatic retard for starting so it wasn't really at 32 degrees while cranking.
This is the stock advance curve on a 1971, 400 car engines, no smog. It is the D0OF-U at the bottom hopefully you can make it out.
All that is cam degrees so double it for crank degrees. Also, you need to add in whatever initial you have to get the total centrifugal. Since this info is for setting up the distributor on a distributor machine.

 

FYI the only reason for the manifold vacuum line to distributor is so the distributor computer knows how to adjust timing based on load/vacuum in table. Table is not in IN HG the table uses kPa at the units.

Do you know how much vac adv there is at idle (manifold vacuum) ?
There is no vacuum advance per se, the vacuum at idle in park is 14 in hg by my vacuum gage but . my vacuum sensor in distributor says 16 in hg which I tend to think is wrong due to my elevation. 14 is about as good as any motor can get up here at idle in park. In gear at idle the vacuum is around 13 on sensor.

Using 20* as an example, when you set your timing at 16*, was that inclusive of vac adv ? I don't have an advance really its all table driven. At idle if I have 20 in blocks of table where my engine is idling that is the reading that I also get on my timing light via the balancer.
If yes, 16* (above) less 20* = 4* retarded, and that's why it would struggle.

Is the 36* above = 20* advance and 16* mechanical ? No mechanical advance really either, 36 is 36 at that vacuum/load and rpm. If I could put a timing light on the motor at 30 mph and half throttle and that part of the table has 36 in that block my timing light would register 36 degrees on balancer.

Whatever your answers are, and as you've confirmed already, you can easily run numbers as high as the engine will tolerate without detonation.

Test drive, adjust, test drive, adjust, until you get the best feeling.

(I ran 20* vac adv + 20* mechanical (so total = 40*) at 800rpm idle (auto transmission) at sea level without any issues.) Thats 20 degrees at idle as mechanical advance is not active at idle, right? In park right?

I'd expect your cruise timing to be higher (40's to 50's), but again, you can dial it all in to get the best feel (and gas mileage).

Double check that the mechanical curve is linear. There is no linear to it, all I do is make sure the table is "smooth" with no extreme changes like say 20 degrees at idle and just off idle 38 degrees. That makes the table spiky???

Table is 12x12 so there are 144 different timing cells with rpm on X axis and Kpa on Y axis.

Did you ever choose and fit a new cam ? I have chosen but cannot get one. That is for my "other" bronco that is getting a frame off.

 

That table is helpful.....thank you..

Basically 17 degrees at idle I assume in neutral so at my elevation I should be around 23 degrees.
WOT is 32 degrees so at my elevation I should be around 38 degrees.

Note fuel octane up here is 85 so it burns SLOWWWWW.

I will input those numbers and see what pops out of the program and test on bronco. Thank you.

 

Explain WOT is difficult? You floor it and then what?
Have you tried a HEI or a Duraspark
With 80 kpa of vacuum, that is 23.62 inches (plenty)
You need a good timing light and verify the actual timing
With 48 degrees total it should blow up (new cars can run up to 60 with EFI but your old 400 not)
Maby your damper has slipped?

 

Have you tried a HEI or a Duraspark Well yes that is why I now have a progression system.

Could have slipped but I found top dead center on compression and taped the balancer and located zero via piston locaton all when I installed new distributor.

NOOOOO Example when engine is at 95 KPA the vac is like 2.2 in hg.

With 7000 feet of elevation and 85 octane that 48 is like 40 at sea level.

 

Let me explain Kpa.......

My atmospheric pressure up here is like 11.5 psi. Not 14.7 like sea level.
A Kpa of 81 is equal to approximately 11.75 psi. so when my vacuum reads 80 kpa its almost equal to my atmospheric pressure 11.5 psi, and when atmospheric equals engine vacuum that vacuum gauge will read close to "0".

Does that make sense?

 

No
The progressive system is your problem right?
Do not know where you are getting 81 kpa of vacuum equalling 11,7 psi on a vacuum gauge
You are dealing with vacuum so that is an entirely different scale
Where 80 kpa is 23.62 inches of mercury
If you put a conventional vacuum gauge on it what does it say?
Read it in inches and go from there?
Makes little difference as long as you are on the right vacuum scale

 

Explain when the engine is at 95 kpa there is only 2,2 inches of vacuum?
That is the trouble and 48 degrees the cause?
Engine is at 95 kpa measured where using what?
None of those numbers is what a tech is going to use to figure out your trucks timing
Not sure where you are headed with this

 

One thing I left out on that D0OF-U dizzy the initial timing on a non-smog engine was 10 degrees. So, the total timing on a stock dizzy would be 38 degrees with another 25 degrees added depending on the load on the engine.

 

Crop Duster thanks for update.

MMO7 I am not sure I can communicate well enough to explain how a MAP sensor works.
This site may help.
Fuel Injection Diagnosis: It's All About the Air | MOTOR

The key take away with a Kpa vs rpm timing table is that when Kpa increases engine vacuum on gauge goes to zero.
Vacuum is a negative number. Kpa is a positive number. 0 Kpa is a perfect vacuum or about -30" Hg. 100 Kpa is atmospheric pressure or 0" Hg gauge pressure which is really 30" Hg absolute.

 

I am a Ford and ASE master tech
No need to explain to me how a map sensor works
Good luck with this

 

Thank you for the details back in post 5.

I watched my friend programming his engine with his laptop plugged into it about 15 years ago, and can remember zero detail !

Where the OE systems have vacuum advance, a mechanical timing curve (from idle to WOT), limiters and springs, I assume the principle is similar in the modern electronic setups.

My terminology and understanding are out of date. Where I say linear and you say smooth, we mean the same thing. (I hope ! LOL)

You’ve got me curious as to how much better/efficient the newer setups are.

Anyway, I’d imagine that the vacuum sensor adjusts timing in the same principle as vacuum advance did.

I completely forgot about engine vacuum plummeting at altitude, so yes, your +/- 14’’ is no surprise.

(Clearly 20* of vacuum advance I mentioned would be more like 10* )

Where I mentioned I had 20* mechanical and 20* advance at 800rpm idle, yes it was in Park.

I said 20* mechanical because it’s the start of the mechanical curve, but yes, I should have just said ‘at idle’.

The sea level benchmark is 10* - 38*, but I wouldn’t be surprised at all if you end up with +/- 20* - 48* (or equivalent with the 12 x 12 settings).

With regard to the cam, I have read good things about Lykins :

https://lykinsmotorsports.com/