Questions about installing woodgas on a carbureted truck with a manual transmission

Hi all,

I am a brand new reader here, and am interested in woodgas as a down - the - road project. My current project lineup is to get Dad’s old 350 running, and purchase an old pickup to put it in. At that time I would prepare to commence working on the woodgas setup. My vehicle preference is to end up with a 1/2 or 3/4 ton 4WD pickup with a manual transmission and carburetor. In my research I have found that pairing woodgas with a manual trans and carburetor is not such a good idea, hence this post.

Ok, on to my questions.

As I understand a guy needs three feet to operate the four pedals. (two accelerators, brake and clutch) Why does a guy need to operate three of these pedals all at the same time? To overcome this apparent three pedal problem, why not just dashmount the gasoline throttle, and use the factory accelerator for controlling the woodgas?

I am sure I will have some more questions, but this is all I can think of now.


P.S. I am not set on having a carburetor or a manual transmission.

Welcome, please search, and read more, you don’t need the extra pedal if you put the wood gas in top of carb, this is the preferred method by most that run carbs.

Good morning Mr. Shmitt and welcome to the site .

There are some pro and cons of runing the gas through the carb vs under it . If I where building a carberated vehicle it would be a toss of a coin whether I went thorough the carb with the wood gas or under it.

My very first wood gas truck was a caberated manual trans . ( 78 one ton ford , floor shift ) I mounted the woodgas throttle on the gear shift .

Driving wood gas with two throttles and manual trans will be like tying one arm behind you in a boxing match . If you are quick and strong enough you might come out OK :confounded:

Different systems “regulate” the optimism…

Woodgas carburation and gasoline carburation can be built independent of each another, and afterwards (in flow direction) mixed at will 0–50–100% or used separately.

Chris has made a model and a video of this system and it is easy to comprehend.
Only one gaspedal is needed; the fuel is chosen at the dashboard independently
with one single knob for woodgas or gasoline in any wanted mix.


I respectfully disagree. Having two throttles won’t really make anything harder, you’ll simply have to pick one or the other - not both at once. Then it’s no different than driving with a single throttle.

If you needed to use both throttles, and the clutch (or brake) all at once, there are other options such as hand throttles or Max’s linkage (below). Or simply mount them close together and hit them with the same foot.

I’ve driven plenty with dual throttles and seldom used both at the same time unless I was cruising and needed extra passing power… at that point you’re not braking or clutching, both feet are free.

Yes, I do like Max’s linkage solution and plan to try it out someday. Here’s a video, showing the principles:

The advantage of two throttles is that it gives you the smoothest way I know to run hybrid. It even beats fuel injection in this regard. It puts the operator in full physical control of the exact ratio of gasoline to woodgas, no computers or fuel pump voltages to fiddle with.

For a full size truck like you’re planning to build, running hybrid will be a consideration - you won’t be able to run 100% woodgas all the time, not at high speeds.

You can’t really blend in gasoline when you go through the top of a carburetor, as the float bowl needs to be drained out before the woodgas will run. This means for carbureted hybrid running, your only real option is to add the woodgas under the carb.


Thank you all for your excellent input, it is very useful to be able to communicate with people who have been down this road before!

I like the idea of running under the carb. As I understand the main drawbacks to this setup are turbulence problems, delayed gasoline acceleration, (how much delay are me talking about?) and height limitations, right? Running through the carb would probably be easier, but I don’t really like the idea of losing hybrid capabilities and getting my carb all gummed up. (with a gummed up carb, woodgas would be the only option until the carb was dismantled and cleaned, i understand)

@Wayne In your opinion, would a throttle linkage like max gasman designed, have solved your “one arm tied up” problem?

@gasman Very nice throttle design I like it! Keep up the good work! Any patents yet? :grinning:

@Chris Your input makes a lot sense! I was thinking the same, but wanted to verify it with someone who had experience. I like your Lego model, very well made and explained!

Thanks again to all of you! Your answers are highly appreciated!


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Good morning L’Chaim

Some of the draw backs on a carb motor are regardless if the gas is running under the carb or through the carb there will be a buildup of carbon in the intake manifold that will have to be dealt with in time .

If you run the gas under the carb there might be an issue with clearance between the carb and the hood.

If you are running a carb you will need to add an electric fuel pump. The below video will show little delay in gasoline acceleration .

Yes , Max and Chris design will eliminate the need for two throttle controls but in general there is a degree of difficulty in wood gas driving that must be learned . Also the only advantage I can think of in the auto trans is operating simplicity .

When the extra skill needed for a manual trans is paired with the extra skill needed for wood gas driving it can be a steep learning curve .

In most cases the vehicle one has is the best truck to gasifiy but if I were buying a vehicle for gasification it would have to be auto trans and fuel injected .

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Thank you La Chaim!

The stepless change-over mechanism from woodgas to gasoline and back has no delay in it, provided the gasoline carburettor is supplied with gasoline pressure. The set ratio is realized instantly.

There is nothing to patent; the change-over mechanism works on steam engine principals.

No need to stack carburettors upon each another;
using horizontal carburettors, one can enter from right and the other from left and joining tangentially into a flat round horizontal “swirl bucket” feeding the intake manifold.

Chris has just built a horizontal double-throat gas-air mixer…


Hello again all,

Yes, carbon on the intake manifold does sound like it would be a problem… A good reason to use an OBDI system…

I am hoping that I will be using a truck with an old enough vintage to have plenty of clearance under the hood.

Why would I need an extra fuel pump? Wouldn’t I just use to factory one and add a switch to its power supply wire so I can shut it off when necessary?

Ahhh, ancient technology returns again…

I will have to look into that swirl bucket idea, it sounds quite interesting…

Thanks again all!


It seems to me, that if you had the undercarb plenum with a woodgas air inlet, You could link the gasoline throttle to the air throttle so opening the gasoline throttle would close the other proportionately. Now then, to drive hybrid, you would just open the gasoline throttle with hand lever, and you would get a consistent percentage of gasoline in your woodgas wherever you move the main woodgas throttle based on what percentage of air was coming through the carburetor.

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Hi, Handy_Andy!

I think you need to draw a sketch of your proposal
to be able to formulate the functions intended.

As the text stands, you are abandoning the footpedal
demand function for gasoline-driving.

As the text stands, you are interfering in the woodgas-air
proportionate 50/50 mixing.

Studying Chris’ video model, one can see that the
footpedal movement for demand is the fundamental one function.

Added to that, the mechanism for proportionate choise.

The mechanism for proportionate choise is shifting
the ratio between: Ready mixed fuels.

Air/gasolinefog and/or woodgas/air.


Good morning Mr. Shmitt,

The vehicles I have gasified with carbs were also old enough they had mechanical fuel pumps . I have used an electric inline gasoline shut off valve to kill the gasoline flow to the carb. One of the problems with this set up is when I forgot to turn the gasoline on before shutting down and to restart was almost like running the tank out of gasoline.

Depending on how hot a day it was and how hot the motor compartment was the gasoline can vaporize and push the gasoline from the inlet side of the mechanical pump all the way back into the fuel tank ( vapor lock ) .

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Perhaps I am as confused as my verbal description suggests, but here is the picture in my head.

Well, think about the results… as you close the air valve, you richen the woodgas. As the throttle opens you’re adding gasoline at a balanced air-fuel ratio. The overall mixture will still be rich, so the motor will bog down. This will get worse the more you open the gasoline throttle (and close the air valve).

The other problem you’ll have is trying to run gasoline. The woodgas and air flaps will have to be shut air-tight in order for the carburetor to function at an idle. Any leaks will cause lean gasoline running.

The correct way to do it is with the air and woodgas mixed before the throttle. This way at any position of either throttle, the engine receives a correct mixture. Since the second throttle is before the plenum, it is much easier to close air-tight for gasoline running as well.

There is an advantage in leaving out the bottom (main) throttle; it will leave the full manifold vacuum over the woodgas and secondary air flaps.
This makes them the “dominant resistance” in their respective flow routes (plumbing).
They have to be ganged together to give 50/50 mixture, as they have the same dimensions and geometry.

This reduces the control “organs” down to only 2;
one for gasolinemix, and the other for the woodgasmix.

If the plenum is a flat cylinder, the woodgas and air can enter it horizontally and tangentially to make a swirl mixing “just in time” before diving into the mainfold.
The gasoline carburettor can also be a horizontal one. This makes a free “poff-lid” available, as nothing is attatched from above…

These 2 independent routes (ready mixed for delivery) can now be handled by the “choise and demand” model that Chris has made a video of.


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Hi again all,

The plenum under carb setup makes sense, it seems to me that that would be the best way to go. (for me) …also really interested in the auto mixer Chris made…

Another question I have; is are there any ideal types of ignition systems for woodgas/gasoline use? I am planning on replacing most all the ignition system stuff on my '73 350 chevy engine soon, so I thought that while i am buying stuff, if there was somthing better than stock than it should be looked into. (got my engine broke loose yesterday!) I am somewhat green to ignition systems, so any other tips are appreciated too.



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Hi L’Chaim,you have an old truck as i too use as learning tool for wood gas. My plentom is about 3" tall and after i built a shorter air cleaner,it still hits the hood.After i bought the plans i see why they like port fuel injected v8 dakotas,I think they are the 93 too 95’s that are best with the timeing adjustable, there is a few guys working on the obs2 timeing problems in the premium sections.on the other hand don manns drives a geo tracker on wood from the wayne keith plans he modified the package too fit all in back of his tracker,he gets much better wood miles per pound,though he dont have much reserve power too pull a trailer.i haven’t finished my truck on wood gas so i have not any results too offer, my truck is 4.3 carb truck.All I do know is that it SUCKS gasoline at 10 MPG. my next truck is 1985 s10 and since it is a 22 r toyota motor when done, it wont have the power take off of the dakota v8s, it may require a little hybriding in some gas too take off fast in traffic,it will work for light loads,transportation.

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Kevin; As I posted yesterday, I am running a 4920 lb. truck with a 4.3. Your correct, I won’t keep up the the Dakotas, but I do travel with out gasoline. Isn’t that the point? As you, I would like to find a good S10 V6. What do you mean it is a 22r Toyota motor? TomC

If you have hight “problems” skip the under- and above-plenum thinking!
Make horizontal tangential feed into a cylindrical plenum!
Acheive swirl mixing with any fuel mix!
Take them all in tangentially horizontally!

There are horizontal carburettors for gasoline, single and doble throat.

Use a single or double throat for gasoline and a double throat for air-woodgas mixing.

For woodgas mixing Chris used a Ford F-150 twin horizontal throat carburettor… 50/50 mix on a golden plate!

Hopefully, you have already read that the 50/50 mix is the best to ignite…

Go horizontal and you have all the room and swirl mixing!

If your ignition system is “failproof” keep it!
If it gives 1" or better sparks, that’s enough!

Advancing ignition with a mechanical distributor is easy, but if it is made by a computer, a thorough investigation of the type and its character has to be taken…


Hi tom ,yes i have a low miles toyota motor home motor and tranny too install in the s10, That i think is about the same weight too horse power ratio as your 5000 pound work truck, the s10 is 3000 pounds and the motor is 2.4 I am still working on finishing my big 4.3 2500 truck project,after i get stoked up with heating wood for winter.
And Max gasman are there any actual pics of an horizonal tangnial plentom,this sounds interesting,i just dont visualize the plentum,and i havent seen any horizonal carbs the size for small block chevy or 4.3 ,ware would one get a salvage yard carb.? Thanks