1990 GMC Serria 5.7L 350 TBI

Dustin Moore's picture
latest configuration (improved heat exchanger) (september 2012))



Chris Saenz's picture

Looks great Dustin! You've

Looks great Dustin! You've been so quiet about your project..... Now we see what you've been up to.

I honestly don't know who's gonna be done first. Not that it really matters; you'll all be done soon enough. In six months there's gonna be double or triple the woodgas truck fleet in the US!!

Terry Lavictoire's picture

Lookin real Good!

Hey Dustin,
Lookin real good!
Won't be long now, if ya wanna come up north for a ride... I could make sure there is some fuel for the return trip.
Great to see you're progress!
I'm waiting for the rain to stop so I can get back at it.
All the best

Mike LaRosa's picture

Dustin, It's gonna be fun at

Dustin, It's gonna be fun at the next gathering(s) .. My biggest problem will be getting a non rusted vehicle to convert to make the next trip. My trailer had a tire go to H on the Argos trip. It was brand new. The center tread just started to break down. I don't think it was bouncing but just simply chinese junk ????? I can't easily cross the border going north, generally speaking, because I always travel with a gun and there is so much crap in my vehicles that I'm bound to forget to remove something :o) . Guess I have to see what part (province) of Canada you are in. I forget where the member's map is. What size engine does the truck have. I'd guess 350 ??? .. Mike

Steve Unruh's picture

Looks Great Dustin!

Looks Great Dustin!
Like the Border Collie too.
MikeL, he says 4.3L V-6. Ain't you the expert on woodgasing these now?
TerryL was 100F the last two days here with the North Pacific jet stream shifting the storms up your way. Next week its supposed to waggle whip back down here. Drats!
Washington State Steve Unruh

Wayne Keith's picture

Hello Dustin,

Hello Dustin,

Looks great!!! When will you be busting the champaign bottle on it?

May you smile with every mile as you give OPEC the old one finger salute.


Mike LaRosa's picture

Hi Steve & Dustin, I guess he

Hi Steve & Dustin, I guess he did spec that and I missed it .. I'm a poor reader and dislexic. I just looked at the pictures. I've got mine up to 70 mph or so a few times but as he's building a WK machine he should maybe be able to push it a bit harder. Chevy trucks are pretty heavy compared to the Dodge Dakota trucks. I'm happy to hear it has a manual transmission. All the automatics I deal with have been a pain in the ars. I like having full control of the transmission but I forget to step on the clutch every once in a while as Anthony Meschke could tell you .. OOPS, I forgot .. I was driving in my sleep that day. With a manual transmission you can continue to pull on the gasifier but with a GM automatic when you take your foot off the pedal it just goes back to idle and if there is a lag in gas production the engine just stalls as the the system isn't designed to keep the engine spinning and put drag on the system. I have to hit the starter key around 2 times in a typical 10 mile drive here. I have the neutral safety switch bypassed but I do have a tach and when it says zero it means zero ... I do a lot of 2 foot driving with the cavalier to keep it stoked up and running as I get to stop signs and the such ... ML

Mike LaRosa's picture

Dustin, Is that as hub motor

Dustin, Is that as hub motor in the rear wheel ?? Any problems with the authorities ? I see the bicycle tag on the side. I believe we can run electric assist under 600 watts here without license and registration. My former employee was arrested at my place and hauled off in handcuffs to jail for riding his here. It was his second charge for operating without a license. They eventually dropped ALL of the charges and had mud in their eyes. They damaged his batteries because the bike sat all winter uncharged. Looks cool but having batteries between my legs under you know what gives me the eebie jeebies. I still have an electric car here (1970 Maverick with an aircraft generator for a motor) but all the batteries are shot and I need to dismantle it and scrap it .. ML

Seems like a lot of smoke

Seems like a lot of smoke leaking. You can test the seal with the fire out using a shop vac hooked up to a dimmer switch to adjust the speed. Try using suction and see if it seals itself or not. Sometimes they do seal on suction and this is what really counts. Some leaks show up on pressure test and some on vacuum, all should be checked and sealed as best as possible for best results. You may spend quite q while fiddling with all this but it is worth it.

This is all normal working out the kinks in a new system.

Richard Cooper's picture

You might try something like

You might try something like a valve spring in the center of your lid instead of a solid bar. Hook the spring to the locking mec. and not the lid, that way you have more even pressure. The way you have looks like it could be pressing more on one side. I have not tested this just what I thought of when I looked at your picture.

OK, I didn't see that picture

OK, I didn't see that picture before. The rim of the lid has a lot of distortions that need to be smoothed out. I put a piece of 1/4 inch braided nylon or fiberglass cord in that groove with hopper goo to glue it in, then pout grease on the rope seal. That spring latch may need to be changed out to a piece of all thread or bolt so you can adjust the tension on the lever. Silicone will not work on the lid. At least not for long.



You might want to use metal pipe for wood gas off the TBI plenum to get out past the engine heat. Rubber tends to collapse and PVC may get soft. Lots of heat in that area right above the intake manifold. The setup looks good. The RV gate valves may be heat sensitive too.

Wayne Keith's picture

Hello Dustin,

Hello Dustin,

If the plenum under the TBI doesn’t work out you may want to try running the woodgas through the TBI and removing the plenum. I have only had one TBI system but put a lot of miles on it (coast to coast and back).
You will eventually have to clean or replace the TBI but you will have to clean your intake manifold eventually anyway regardless of which system you choose.


PS, I had a switch for each injector.

Once she is lit and runs low

Once she is lit and runs low on wood, make sure you aren't pulling on the gasifier when running on gasoline. An empty fire tube heats up fast if you have leaky wood gas valves. Another trick new wood gassers like to do is run hybrid. Becareful you are not out on the highway and run down the wood in the fire tube or your tube will look like this.

Wayne Keith's picture

Hello Dustin,

Hello Dustin,

Congratulation on your truck.

It would be handy to have a spare TBI and should take but a few minutes to change it out if necessary.

The TBI can be clean somewhat with compressed air. You can blow the carbon build up down in the intake manifold. It doesn’t seem to hurt the motor.

One question on the ignition timing. Are you advancing it any?

Terry Lavictoire's picture

Howdy Dustin,

Howdy Dustin,
I suspect the small leaks are the problem... Especially after the grate. It takes very little air infiltration to seriously degrade gas quality. Gentle positive pressure in the system and very soapy water will find most leaks.
The timing should help after the leaks are dealt with.
You are most of the way there!

Chris Saenz's picture

Leaks leaks leaks. If you're

Leaks leaks leaks. If you're losing 5" of vacuum between the rails and the air cleaner, there's something amiss. Either a restriction in the plumbing or some air leaks. Actually that speed sounds about right for the vacuum levels and the restriction size. You need to pull closer to 15-20" at the rails to get up to 50-55 mph in third gear, just a guess and that will vary based on gasifier conditions. When you open up the restriction (LATER not now) there will be more power overall.

Acid test: Are you able to kill the truck by running too rich? If not then there's still work to do.

Sounds like leaks. Weak gas.

Sounds like leaks. Weak gas. Is the restriction plate all the way at the bottom of the tube? getting any puff backs while trying to accelerate?

Some leaks will show up on suction and others will under pressure. It took me months to get all mine stopped. Once you fix a bunch of them, more show up because the weak spots get more stress and let loose. Pipes that flop around will develop leaks. If you have a pipe going up over a rear axle that may crack or leak after a few drives.

Chris Saenz's picture



How's your wood supply? Nice and dry? What size chunks are you running?

Since you can kill the engine with the gas, we'll set aside the leaks for now. I still don't like the pressure drop from the rails to the engine. But I will admit I've never measured it at the engine. Check for blockage, flexible pipes collapsing under vacuum.

Just went back over your pics, do you have a single 2" woodgas line to the engine? That could explain the pressure drop. You should still be able to pull harder on the plumbing though. Try at an idle in neutral and see what's the highest it will pull on each of the gauges.

Good ratio on the hopper/cooling rails there. No plugging, nice and loose. What temps are you getting?

Steve Unruh's picture

Hmm. I will only comment on

Hmm. I will only comment on the fuelwood - cedar. I have gasified with Western Red Cedar. Works ok. Probably at the far end of the spectrum of usable woods. Need to size largish. Have a very mild grate action to keep from crushing/crumbling the super soft char. It IS low ash so not a problem there anyhow.
Yes low density and weight so getting 2X the volume of it to feeding trough any ledges/tapers/edges above the nozzles versus denser woods is the only real fuel specific problem area I've seen. Hooper goo and condensate sure smells nice.
Steve Unruh

Chris Saenz's picture



Everything you're telling me sounds good, and that's the problem. Pipes sized right, temps OK. Wood is dry, char is loose. You can stall it with rich gas, meaning you have plenty of room for setting the correct mix. An O2 sensor can help here but isn't critical. If it seems touchy then you may want a longer lever arm on the air valve.

Idle speed is a red herring; the computer will have a hard time controlling idle speed on woodgas. You want to use a string tied to the gas pedal and a friction knob to adjust your idle speed. You say it idles OK right down to 300 RPM, that's good.

So your problem seems to be that you can't pull hard enough on the gasifier. All the gasifier sees is a light load, and so it's not producing much gas. Temps remain low, vac readings stay low. Even at full throttle you can't pull any harder on the gasifier.

This is crying out "restriction" to me. I had literally the same situation, I used a flex pipe under the hood that was collapsing under vacuum. Effectively limiting me to half-throttle operation.

I just can't figure out where your restriction is, everything sounds right from here. Have you got a vac gauge on the intake manifold? This can be revealing. Remember this is inches Hg not inches of water. Trace the vacuum through the system, just like you would an electrical short.

This does seem like an AHA! moment waiting to happen. Hoping you'll find something trivial that caused the problem, and your truck will finally be up to full power.

Chris Saenz's picture

Yes collected water will

Yes collected water will restrict the flow. Is the plumbing sloped back from the hay filter to the condensate tank? If not it will collect water. In any event everything should be able to run into the tank when you go up a slight hill.

Hay filter is among the easiest pieces to rebuild or replace if need be.

Chris Saenz's picture

Ouch. Glad you caught the air

Ouch. Glad you caught the air leaks, and hope nothing overheated before you found it. Guess you'll find out over the next few drives. From what you said before there wasn't much temperature, so lets hope that means no damage.

The knob and string solution is very simple, and works a treat. Tighten the string to pull the pedal and raise the idle, and loosen it to let the throttle close and lower the idle.

Mike LaRosa's picture

Dustin, I just introduce the

Dustin, I just introduce the woodgas into the air cleaner on my chevy and have a foam on chicken wire frame filter in the canister for a final filter and for running on gasoline. I did add an anti dieseling solenoid from an old quadrajet to bring the idle up for woodgas. It is set at 2500 rpm on gasoline but settles around 1000 to 1200 on woodgas.
is a picture of it. It was very easy to rig up to the throttle body. I use it all the time. I also have switches to turn off the fuel pump and or injectors.

10-15 inches in the hopper

10-15 inches in the hopper sounds high. What does the bottom of the gasifier read? Expect more leaks to show up as the system vibrates from all the speeding around. You should be able to run 65 mph on that truck on flat ground when the system is running right. It may take some more time to learn how to operate the gasifier to get that result without sucking in your cans. Gasifier should be larger for that truck weight and hp so take it easy and don't burn it up.

A thermocouple right as the gas leaves the gasifier will detect leaks in the bottom of the gasifier instantly. A big change in temperature shows right up and you can shut down the truck before tearing up the insides of the gasifier. The heat exchanger thermometer is less sensitive and takes longer to show the heat spike.

High vacuum [fast accelerations and inexperience] causes those ammo can sides to bend and pulls the metal away from the rubber seal. A spacer inside to prevent the metal from moving will help. Also household insulation to protect the rubber seal from the hot char will help. Once those things do leak they usually keep leaking so I would test them regularly with soapy water on pressure and smoke from a piece of rope or something on vacuum. You will see it around the hinges too if they warp. If there is white ash on the char it will come out first and get buried by all the other char so it may be hard to see any ash from leaks.

Mike LaRosa's picture

Dustin & Bruce, Have to run

Dustin & Bruce, Have to run for the day .. gasoline .. ouch .. Dustin, It only took a piece of folded and drilled steel strap and a couple of bolts to mount that solenoid .. Bruce, I remember that after your visit to Wayne's you went home and built rectangular instead of round. I wondered how that would hold up with the sides flexing. Thanks for posting about the struts. I brought a few ammo cans back from Wayne's bus last visit but have yet to use them for anything besides storing explosives / ammo. Dustin, your engine will pull like a 350 minus 2 jugs. Just have to spin it faster to get the same power. Most of the older chevys I had with 283s and 327s and 400s were light on 2 cylinders anyway :o) .. Mike