Ignition advance: why and how

A National Geographic theme on woodgas few years ago made the viewers believe that a woodgas powered car would not start when the ignition is not advanced. This is misinformation, because ignition advance only helps to gain more power especially at higher rpms. An underpowered engine does not need ignition advance and certainly not on low rpms. In such a case only exhaust emissions will benefit of any advance. Lucky people with a high hydrogen yield in the woodgas will need less or no advance.

The usual methodes for advance are turning the distributor manually of have the electronics take care of it.

I have the '70s Chevy bigblock with a high Edelbrock intake manifold and the mixer on top of this. So almost no access to the distributor. A modern electronic distributor with the coil in the cap. It has a vacuum pot for advance which is of less use now, because it cannot take the right vacuum like before near the throttle valve. Each feed (LPG, gasoline and woodgas) has it’s own throttle in my setup.

Now my suggestion: what if I use this vacuumpot for woodgas advance, perhaps in combination with a little too much advance on the standard setting. Does anyone know how much advance can be obtained with the vacuum pot? Using the higher intake vacuum on woodgas, perhaps with a vacuum multiplier. I know Vesa uses a constant vacuum source to pull to maximum advance, but I do not have such a device. In my opinion it would be elegant to use the load dependend vacuum in the gas line combined with a vacuum multiplier.

Any thoughts about this methode?


Dj, a quick answer would be 16 to 30 deg advance depending on your model. Here is a link


It also shows starting hg". I imagine you could disassemble and replace the spring with a lighter one to lower the start if needed.

Yes. And a handy clever man like you DJ could move the vacuum pot pull arm closer to the shaft center for a quicker responce and allow a widen out the plate movement to get as much as ~45 degree advance. Since you are only going to be using the gasoline for starting and trundling in and out of buildings/parking with the higher knock resistance of propane/woodgas lots of mechanical advance springs, weights, shaping info out there to get quicker advance from that direction too.


Opps. Forgot to mention. DJ your constant vacuum source on your cassis is the back side of your power brake booster. Tap into that for a constant non variable source. OR, alla Ford/Chrysler/GM emissions vacuum controlled systems set up with your own manifold check valved supplied vacuum reservoir can. The vacuum multipliers that I have seen internally either use sucked in air or manifold vacuum past a suction orifice to do this. Specialized. Spendy. And contamination troublesome. Here they had a nasty tendency to 30-40F (-1 to +4C) frost up and clog.


Thanks for the link. Shines a light. American engines are new to me.


Constant vacuum would ask for some control on idle or low rpm. Increasing vacuum when more asked power is easier to handle. Setting once and ready. But do I need 45 degrees extra advance? Literature tells me 15-20 would be enough. In practice I’m a layman on this, because the Volvo just doesn’t give a damn weather I advance 20 degrees or 0, top speed remains the same.


I only offered an existing source for constant vacuum for any reason you would want. American vehicles use this much for climate control door movements.

How much advance can a big V-8 engine handle on woodgas?? WayneK. recently answered on John Wells project line here measuring 70 degrees maximum advance on his all electronic distrubutorless EFI Dodge V-10 and wanting the more that he can get on his Dakota V-8’s with distributor turning in addition to their electronic self-control. Terry’s linked article speaks of 52-54 total degrees maximum ON GASOLINE for your Chevy. So yes on woodgas, and maybe even propane, you could benefit from more than this total 52-54 factory limitation. Vacuum advance doing this would give from the drivers position controllability. You will not know until you try, eh? Thinking about this again a widen range of possibility could be also controlled with an inside the distributor movable plate stop pin.


I am doing my research and trying to understand what the guys are doing with regards to timing. I see references to advancing the timing in both the forum text and mentioned in videos, yet none of the videos I have found thus far show how this is being done.

On the older carburetor vehicles I assume they are adjusting the distributor cap?

I am confused what (if anything) is being done with the newer fuel injected vehicles. For example on the Dodges; is Wayne simply cutting power to the fuel pump via a switch and letting the stock computer re-tune the timing for the woodgas or is he using some type of performance tuning module such as a Bully Dog or Edge unit to advance the timing? He seems to switch between woodgas and gasoline with just the levers and toggle switch. Some clarification on this would be greatly appreciated!

DJ - if your engine has the GM HEI ignition there is another module you may want to try. I don’t have the part number, but it was used in Pontiac firebirds with a 301 cid turbocharged engine, in model years around 1979. It has a fifth wire, usually there are only four. when grounded it retards the timing 10 degrees. In the turbo engines it is used with a knock sensor to prevent detonation under high boost. If you use that module and set your static timing with it grounded , when you flip a switch and unground it you advance your timing 10 degrees. It is much easier to start a hot Chevy with the timing pulled back. With some tweaking to the vacuum and centrifigul advances, you should be able to get enough advance.
Also there are 2 weaknesses in the HEI setup. Always carry a spare rotor as they occasionally burn through the rotor and ground to the distribitor shaft. And they do suffer some module failures due to excessive heat in the distribitor. You can mount the module on the fenderwell on a heatsink and extend the wiring harness to it. I have a ford truck with a 5.0 engine. The efi was totally shot when I got the truck. I converted to a carb and installed an earlier distribitor with internal advances in it. I have an HEI module mounted on the wheelwell and it does a great job of firing the Ford engine. Another advantage to remote mounting is you can mount a second module near the first one. If you have a module failure, switch the wires to the second module. No tools needed and yoe are going again in a short time.

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Hi Mike Carey, I wish we still had that stuff to play with here in Wisconsin but it has already been melted. I hope some of the guys down south can take advantage of the tips. Very good advice. Things used to be so simple … I still have an old HEI distributor etc in the shed (GM of course) … Mike LaRosa

Hey HenryA.
Most early electronic fuel injected vehicles have distributors with internal or external computer control. Change over to no distributor systems began in the early 90’s and most all were distributor-less by ~2003.
Most fellows do set up a lever/cable/rod set up to be able to early way manually be able to turn the distributor while driving from the dash.
Electronically controlled ignition timing systems either distributor or distributor-less can be either with a factory Ford “SPOUT” circuit, GM “Pink Wire”, Chrysler/Dodge (varied colored) “IG bypass wire” have the timing knocked back from an over advanced woodgas fuel setting to a less advanced cranking/starting base setting. As MikeC. said different ways to spoof the factory electronic systems into additonal advancing or retarding if you dig into the specific system. Or . . . as you said, have a system specific added on after-market adjustment system added on.

What’s your pleasure? GM? Ford? Chrysler/Dodge? Import? Year and model? Engine?

Steve Unruh

Thanks for the reply. I must purchase a vehicle for conversion, both because I have no truck at the moment (a man needs a truck right?) and because the wife will own my behind if I “mess” with her car or my Scion XB (she says the value is too high for me to be messing with them, and they only have little 1.4L engines) - What I heard her say was: “You have my blessing to purchase a truck!”

That said, I am following up on a possible 95 Dodge V10 4x4 here locally, she’s pretty beat up but that’s an ideal first truck (and winter beater, I’m in East Lansing, MI - rust belt central). $1500 is the right price too, wish me luck! If someone beats me to the Dodge, my backup vehicle is a 91 Chevy 3/4 ton ext cab 454 bb 4l80e automatic 4x4. I’ll have to go look at this one, not sure what has been done under the hood on this one. 7.4L of displacement is right behind the Dodge 8.0L and if I can find one from the 90’s models I know them inside and out. Guys in this area tend to hang onto their Fords until they are dead beyond repair, so not a lot of desirable Fords in this area (right now anyway).

Most of the chevy trucks from the 90’s have TBI (or carbs, depending on who you get one from and what they’ve done with/to it). I was searching the web and there aren’t a whole lot of features that you can program on the fly (such as timing) with the CPU’s in the pre-99 Chevy trucks (still researching that, could be wrong). The newer ones (99 and up) are wide open to everything you want (with say an Edge Power programmer) but not the 90’s models.

I was thinking that Wayne was using a cable to tweak the distributor on his ford work truck (hard to tell from his dual fuel switching video). It looks like a lawn mower throttle cable mounted on the steering column to move the distributor back and forth? The distributor-less or electronic systems have me a bit flubbed though. What is typically done with the GM “Pink Wire” or the Chrysler/Dodge (varied color) “IG bypass wire” ?

Also, a related concern is the reading I have done regarding the soot that has to be periodically cleaned or burned out of the intake manifold. - I know I want a vehicle with a metal intake or one that can easily be changed to metal, and It sounds like the multiport injection system offers much easier access to the intake than a carb system (for this task). This of course dictates the method required to handle timing advance.

My research is showing me that Wayne likes the 92-95 ish Dakotas for good reason! I do however need to be able to tow with my truck and tow more than the Dakota is suited for, so I’m leaning Dodge v10 (largely because Wayne has proved this works) or large Chevy (right in my comfort zone / knowledge base). I’m sure someone is going to ask, my towing requirements are not unrealistic. I have a flatbed auto transport ( 16’ ) that I haul everything (including cars) on, my max rated load (trailer included) is about 7500lbs. At the moment I’m borrowing trucks when I need to use it, and it’s getting old quick. Based on the information I have come across, a large displacement engine should be more than capable of hauling this size load on Woodgas, just not quite as fast as I would always like.

I just want to be sure I understand the timing issues and maintenance concerns (soot burn out) before I make my purchase. My intent is to have as much accurate information as possible before leaping into this with my wallet. I know there will be headaches along the way, but I’m hoping that due-diligence on the front end will reduce the overall frustration of the experience (yeah right).

Henry, My guess is that 91 will rot out before you even have to begin to think about cleaning the intake manifold. With the tbi, you should be able to wash it out periodically anyway. That is tougher to do with mfi as they inject near the intake valves so all you will be able to do is wash off the intake valves. I used to have trouble with the butterfly sticking on my 91 olds with mfi. With that big engine it may be tight getting your pipework into it. I bought my 93 with the 4.3 because I saw all kinds of room under the hood. You will definitely want to rotate the distributor on that from the cab. I change timing all the time. The computer handles some but it’s 2 ranges between woodgas and hybrid. I’ve attached 2 pictures that might help if you get that 91.

I must have clicked a wrong button … Here’s the other picture. Mike

Hello Mr. Austin,

On my old ford truck (1984 I think?) 460 cid I use a choke cable to rotate the distributer.

On the 95 V-10 it has no distributor, coil packs only. When I switch from gasoline to wood gas the computer advances the timing 30 degrees above the stock gasoline timing. It makes the transition from gasoline to wood and back to gasoline very smooth. I think the gasoline timing is 10 degress BTDC so it is idling at 40 degrees BTDC on wood. When I rev the motor the timing light goes blank so I don’t know if it advances more as I rev?

On the Dakotas V8 I have a cable to rotate the distributor. The stock timing on the truck is 10 BTDC.
When I rotate the distributer the timing jumps up 45 degrees from stock . The truck idles rough for a couple of minutes until it warms up. The best I can tell the fire jumps to the next peg.

I made this video for you this morning


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Hi back HenryA.

MikeL just covered well the how and why to distributor turn/adjust. He knows about the GM “pink wire”. Lets you cut out the computer commanded variable timing control and fall back onto a fixed ignition amplifier module timing with just an added in flick of the switch. Same as the Ford 'SPOUT" connector and Chysler/Dodge “IG bypass” wire. Early 80’s-90’s systems only.

Shame about your local Ford PU situation. They were the first to really effectively modify their 460/7.5L big block engines to good port fuel injection and roller tappets cams in the 88=89 time frame. GM dawdled as you have found on their switch over. Chrysler/Dodge dropped the 440 engine and for near ten years lost the big engine gasoline truck and RV market until the V-10. The Ford smaller over complicated SOHC V-10’s for a tow rig don’t even bother.

Ha! Ha! Intake soots: as a fellow never driven a mile on woodgas I will not comment on this. Leave the TBI vs Port injection soot cleaning pro’s and con’s to those who have ran the hours/miles/pounds of woodfuel to have made the soots buildups and had to deal with it.

Steve Unruh

I have a better idea now what to expect with timing. I’m also relieved to see that I don’t need an expensive, fancy performance tuning computer and what not!

I think I’m leaning Chevy at the moment, which means I’ll need a distributor adjuster cable similar to what Mike and Wayne are using and a toggle switch to interrupt the pink wire to the distributor if I understand Steve correctly.

Thanks for helping me understand what’s required and what is being done. And thanks for the video Wayne. Much appreciated.

Henry, I have a switch to disable the computer control of the advance but I rarely use it. On my 91 S-10 it was under the passenger kick panel but on my 93 1500 it was in the relay area under the hood. The computer does a great job for the variations it faces so I let it do it’s job. I have a hole drilled through the hump in the firewall and run a rod to the distributor lever. inside the cab I have a twist arrangement and a lever that pivots on one of the bolts that holds the steering column cover. This might help you understand what is in the pictures I posted. Click on the pictures to get the full resolution ones. Mike

Know what you’re talking about with hauling/towing requirements. Finding a big gas engine with a granny gear is going to be a must. A bit off topic (at least I was running SVO)… but couldn’t resist adding this pic of my 1987 Ford hauling a dismembered 1994 Ford 7.3 diesel, it’s all in the bed of the truck except for the axles/tires. I won’t say how much it weighed, but I didn’t get over 40 mph on the way to the scrap yard. It did get a few smiles out of the neighbors.
William :slight_smile:

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