440 Timing

[///Matt]

Just drove it... it definitely needs more initial back in it. Starts well, idles great, and if you treat the pedal nicely it drives fine... but pushing it from a stop or flooring it while cruising both result in a noticeable bog that wasn’t there before I dialed it back. But at a steady cruise, the motor is running smoother, less surge and jumpiness.

This is all with it hooked to ported vacuum. May switch to manifold without changing timing at see what it does.

Oh, and the upper rpm range while pushing it seems maybe a bit stronger, less noisy.

Is it perhaps a case of “had good initial before but too much total”, and indicates that I need to raise initial back and limit the total?

And if I wanted to change the amount of vacuum advance delivered, it’s as simply as turning the whole vacuum can? Or is it an internal change/adjustment?

 

[Bill Monk]

Just drove it... it definitely needs more initial back in it. Starts well, idles great, and if you treat the pedal nicely it drives fine... but pushing it from a stop or flooring it while cruising both result in a noticeable bog that wasn’t there before I dialed it back. But at a steady cruise, the motor is running smoother, less surge and jumpiness.

This is all with it hooked to ported vacuum. May switch to manifold without changing timing at see what it does.

Oh, and the upper rpm range while pushing it seems maybe a bit stronger, less noisy.

Is it perhaps a case of “had good initial before but too much total”, and indicates that I need to raise initial back and limit the total?

And if I wanted to change the amount of vacuum advance delivered, it’s as simply as turning the whole vacuum can? Or is it an internal change/adjustment?

Adjusting the can should give you enough

 

[Dragon Slayer]

OK, my bad, but I still don't know how you are getting 50 (all in) if you are connected to manifold vacuum. Manifold vacuum should decrease by the time you are hitting 3000 rpm

Would it drop if in neutral and garage test? Throttle doesn't need to open much no load like that. He said he saw 18-20in vacuum during test.

 

[Dragon Slayer]

Just drove it... it definitely needs more initial back in it. Starts well, idles great, and if you treat the pedal nicely it drives fine... but pushing it from a stop or flooring it while cruising both result in a noticeable bog that wasn’t there before I dialed it back. But at a steady cruise, the motor is running smoother, less surge and jumpiness.

This is all with it hooked to ported vacuum. May switch to manifold without changing timing at see what it does.

Oh, and the upper rpm range while pushing it seems maybe a bit stronger, less noisy.

Is it perhaps a case of “had good initial before but too much total”, and indicates that I need to raise initial back and limit the total?

And if I wanted to change the amount of vacuum advance delivered, it’s as simply as turning the whole vacuum can? Or is it an internal change/adjustment?

If you have the cannister that is adjustable with an allen head then yes. You can limit it. But you might want to just go to 12 initial and try it.

 

[Bill Monk]

Would it drop if in neutral and garage test? Throttle doesn't need to open much no load like that. He said he saw 18-20in vacuum during test.

still should see a marked decrease in manifold vacuum at 3000 rpm. It won't be 0 but I would think to low to actuate the vac can arm

 

[///Matt]

Made some changes.

Re-tuned the carb idle-air bleed and reset the idle speed. Got my idle vacuum up to 14”@950.

Set initial timing to 18*, and it gets all in mechanical at 37*@2600.

Dig this nonsense though, testing the vac adv:
My vac can holds vacuum, as tested on my hand-pump/gauge.
It does nothing to the timing until 15” from the pump is applied, at which point it begins advance.
It has an full-sweep advance (at 23-25”mg) of 22*. That’s twenty two. Of vacuum advance... as I watch the timing run up from 18-40* while I manually apply vacuum to the canister. If I attach it to manifold vacuum, even though I read only 14” coming out, it advances at idle leaving my initial sitting at 30* or so @950rpm.
And then revving with all attached nets me an all in of 59* @2600.

And the motor really doesn’t seem to like that. As you rev into the mid-2k range, it gets bucky. If I disable vac advance, it revs much more crisply and smoothly.

So for now I have disabled the vac advance.

I feel like 22* of vac adv is way too much. I don’t think mine is adjustable, but by all means, correct me. I’ve uploaded a picture of my diz for direction. I believe it is an MP electronic.

 

[Bill Monk]

Made some changes.

Re-tuned the carb idle-air bleed and reset the idle speed. Got my idle vacuum up to 14”@950.

Set initial timing to 18*, and it gets all in mechanical at 37*@2600.

Dig this nonsense though, testing the vac adv:
My vac can holds vacuum, as tested on my hand-pump/gauge.
It does nothing to the timing until 15” from the pump is applied, at which point it begins advance.
It has an full-sweep advance (at 23-25”mg) of 22*. That’s twenty two. Of vacuum advance... as I watch the timing run up from 18-40* while I manually apply vacuum to the canister. If I attach it to manifold vacuum, even though I read only 14” coming out, it advances at idle leaving my initial sitting at 30* or so @950rpm.
And then revving with all attached nets me an all in of 59* @2600.

And the motor really doesn’t seem to like that. As you rev into the mid-2k range, it gets bucky. If I disable vac advance, it revs much more crisply and smoothly.

So for now I have disabled the vac advance.

I feel like 22* of vac adv is way too much. I don’t think mine is adjustable, but by all means, correct me. I’ve uploaded a picture of my diz for direction. I believe it is an MP electronic.

View attachment 678423 View attachment 678424

There you have it. Contact Don at 4secondsflat and he can hook you up with a good vac can

 

[Dragon Slayer]

I have seen vacuum canister with 13 on the arm which gives about 26 at crank. But there on engines not using that much initial, and mechanical doesn't come full in until 4500RPM. 37 seems high for total without vacuum, but if your engine likes it then that is what it should be.

If your canister is an adjustable one, there should be a set screw inside the fitting that the vacuum hose attaches too. I think 3/32 allen wrench but that is from memory.

 

[biomedtechguy]

I'm getting one of these asap.
https://progressionignition.com/
Here's an ignition MAP the app generated from my entering basic parameters:

It's all programmable from a smartphone or tablet.

 

[Cranky]

I'm getting one of these asap.
https://progressionignition.com/
Here's an ignition MAP the app generated from my entering basic parameters:
View attachment 1080248
It's all programmable from a smartphone or tablet.

Is the left column ambient temp?

 

[biomedtechguy]

Is the left column ambient temp?

Honestly I don't know. I just downloaded the app about 2 weeks ago, chose "work offline" since I don't actually have the distributor yet, I had to turn on Bluetooth regardless, and I entered some basic parameters and BAM it produced a basic ignition advance MAP to start out with.
I was thinking that it may be a Manifold Pressure figure as they measure it in kPa (kilo-Pascals) I believe, not in inches of mercury.

 

[biomedtechguy]

This is the table that the user enters values into to generate a "base map" for ignition timing.

 

[Cranky]

Honestly I don't know. I just downloaded the app about 2 weeks ago, chose "work offline" since I don't actually have the distributor yet, I had to turn on Bluetooth regardless, and I entered some basic parameters and BAM it produced a basic ignition advance MAP to start out with.
I was thinking that it may be a Manifold Pressure figure as they measure it in kPa (kilo-Pascals) I believe, not in inches of mercury.

I've had the pleasure (displeasure) of tuning on a couple of engines with pretty low compression numbers and ended up with 50 degrees total timing before the thing would run good!!! And yes, it was checked with no less than 3 different timing lights. It was nuts! The first time really had me scratching.....my head. The second time, I just went with it lol. The first engine was a 440 in a 67 Coronet and really didn't get a good 1/4 mile ET repeat since it did nothing but spin the tires and the 2nd one was a 318 Demon that ran a best of 13.51 @ 102. The teen came out to have 7.8-1 and the 440 was right at 8-1 and recorded all over mid 12s.

 

[biomedtechguy]

I don't know the actual compression in my 440, but it likes 93 octane premium fuel. It's a 71 block stock bore w/"6 pack" rods and forged crank w/flat top pistons and "eyebrow" valve reliefs with 452 heads. I don't know if the heads have been milled or shaved, but with factory stamped rocker arms and hydraulic lifters with what is believed to be the 292°/.509 Purple Stripe cam the stock pushrods from Mancini work fine.