Vortec Head Timing With Progression Ignition

Howdy!

Anyone running a Progressive Ignition system with Vortec heads? I'm trying to fine tune the timing curve as I think I'm leaving some performance on the table.

For those that don't have this kind of ignition, I'd still like your opinion. I've read that Vortec heads don't like or need anything over about 32°. Is that WITH vacuum advance? Or BEFORE vacuum advance? I can also set HOW MUCH vacuum advance I want, and where I want it to start and stop. If you haven't figured it out already, I'm a noob when it comes to timing. LOL

Thanks in advance!!

32° is going to be your total advance, that is your base timing + mechanical advance.

So if you are base timed at 12°, you want 20° of mechanical advance to get to 32°

The vacuum advance should be disconnected (carb port plugged) when setting both initial and checking mechanical advance.

Vacuum advance adds timing in high vacuum situations like cruising steady speed on the interstate. Punch the throttle, vacuum drops and the vacuum advance pulls timing back be back on the mechanical advance. Wide open throttle for example will be all mechanical advance as there is (or shouldn’t) no vacuum at WOT.

Is this a stand alone system or part of an EFI? I have the same capability with my pf-4. It's nice to tap your phone for adjustments rather than turn a wrench. I also have vortecs (@Rusty Nail favorite). Set base at 12 and total at 32 like said above. Getting the curve right is the tricky part that determines drivability.

Old60Driver said:

Howdy!

Anyone running a Progressive Ignition system with Vortec heads? I'm trying to fine tune the timing curve as I think I'm leaving some performance on the table.

For those that don't have this kind of ignition, I'd still like your opinion. I've read that Vortec heads don't like or need anything over about 32°. Is that WITH vacuum advance? Or BEFORE vacuum advance? I can also set HOW MUCH vacuum advance I want, and where I want it to start and stop. If you haven't figured it out already, I'm a noob when it comes to timing. LOL

Thanks in advance!!

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maybe start with a base timing map from an L31 truck/suv/express van from 96-2005?

I know the Vortech's like less timing like the others have stated. I had to swap springs on the dizzy. I 'm using a lite, and a heavy. I was getting some pinging with both lighter springs. I run 87 octane gas. I have to look up my timing specs. It was last year when I dialed the truck in. With the vacuum advance run as much as you can until the vacuum drops or the truck pings, losses power etc. You will need a vacuum gauge to do this and a nice level road and some time for trials. Check out Unity Garage on You Tube. He is running a dizzy like yours.

SquareRoot said:

Is this a stand alone system or part of an EFI? I have the same capability with my pf-4. It's nice to tap your phone for adjustments rather than turn a wrench. I also have vortecs (@Rusty Nail favorite). Set base at 12 and total at 32 like said above. Getting the curve right is the tricky part that determines drivability.

Click to expand...

it's a stand alone system; I'm still rocking the Qjet!!

Bextreme04 said:

maybe start with a base timing map from an L31 truck/suv/express van from 96-2005?

Click to expand...

That's a great idea, thanks!

Vacuum advance is not related to performance tuning, since as soon as you open the throttle the vacuum will drop and the vacuum advance goes away. You can mostly plug the lone and ignore it when first setting base and mechanical timing.

Vacuum advance is there to improve the burn at steady speed conditions and improve gas mileage. In general, you increase it as much as the engine will tolerate without pinging at light throttle. Most stock VA cans add about 18-20 degrees, but there are older performance models that top out at 10-15. Most of the “adjustable” vacuum advance cans allow you to adjust the vacuum point where it starts to activate, but changing the max requires a bushing or stop inside the distributor.