DJ's C-20 454

Hi all,

Long time no see. Some of you will know me from the Yahoo groups or have visited my website. Recently it started itching again and I bought a for Dutch standards very difficult to obtain vehicle. A '73 Chevy C-20 pickup truck with a 454 engine. I know, on your side of the pond such vehicles are shredded or left to rot… But me and my wife are happy with with this simple, staight forward truck, although there always will be a Volvo around too.

I am in the midst of building the gasifier. Again full stainless. Many details from the Volvo gasifier are used again. The hearth is different, hopper and filter will be square, but following the contours of the cabin. No dry filtering this time. Dry filtering is superb, but do not want to have it destroyed by only one mistake. The truck will also be driven by a lesser experienced woodgasser.

Pics will follow as soon as possible.


Hello Dutch John and welcome.
There has been some interesting talk in different topic/project lines about the needed ignition advance for woodgas running these big engines.
Look forward to seeing some of your underhood pictures.

Steve Unruh

DJ, Thanks for checking in with the gang again … That is definitely a “cash for clunkers” car here but you will be able to race Wayne when you get it done “young man” … Please post occasionally on the yahoo stuff … It’s not the best forum but it is what it is and there are very few others … Thanks, Mike LaRosa PS, wish I could remember your real name … I wrote it down years ago … Cyclone and a good hay filter should be enough for that engine … They love soot and it keeps them from burning oil … packs the rings up …

OK, under the hood most is done. I made a distribution box on top of the intake manifold. Mixing tube and backfire lid on top. Right behind is the woodgas inlet, right in front the air inlet. Upstream (black painted) a manual choke and a vacuum controlled one. Air filter will come behind the headlight.

Left in front is the IMPCO LPG carb, now tilted 90 degrees. When driving on woodgas or petrol, the 3" ball valve is closed. Left back is a Stromberg petrol carb for emergency, starting help and boost. Ball valve is open when driving on woodgas. The petrol throttle is only manually operated. It gets air from the IMPCO air filter. It was the original GM filter housing, but most of it ended in the trash bin.

The gas pedal operates the IMPCO. When the ball valve is closed to drive on woodgas, the linkage between IMPCO and woodgas mixer is fixed by a pin. The linkage is a rod that can slide in a tube. The pin connects them. The throttle valves of the woodgas mixer have there own manual idle setting, because when driving on LPG, the throttles are not allowed to leak dilluting air.

This is about the same setup as used on the Volvo. The vacuum control allows an adjustmentfree driving. Except when the gas quality changes, it needs adjustment, while the vacuum control does the fine tuning.

Getting the gas pipe along the chassis, through the fender and around the steering column was rather a challenge. I never make 90 degree elbows by cutting a pipe under 45 degrees. I always take smooth 90 degree welding curves (right word?) For a lesser angle the curves are cut up. It takes one welding seem extra and a bit more money for the welding curves, but the reward is a lesser pressure drop and a good looking tube.


Nice work DJ. Now let’s see some photos of the 90’s you’re describing. Keep up the good work.

Chris F.

Pictures are worth a thousand words. Thank you DJ.
The vacuum diaphragm really interests me. I know Max suggests them on every system. I need to try to attach one to my Ranger.
Could you show a better picture of this linkage?
Thanks in advance,

This is the best I have. The blue membrame is now changed for more elastic pond foil. Needs a bit heat to stretch. The controller is rather small, but worked well on the Volvo.

Valves are easy to make if you have (access to) a lathe. Take thick walled pipe and lathe the inside to the desired size. Take a rod and bring it to the same diameter. It should fit very tight in the pipe. Cut thin slices under 15 degrees from this rod for example with a band saw: your valve flaps. For bushing I used 12x1 mm coppeer water tube, an end cap and 10 mm rod as axle.
All cutting is done with a small angle grinder. I desperatly need a plasma cutter…


DJ, on the plasma - I got one for $300 and it’s doing the job fine. So nice to cut with. Look on Ebay for Lotos 5000D (or similar).

No way back anymore: I cut the bed. The actual hearth is mostly below the bed, because I want a low gasifier. This forces the hearth diameter to be on the slender side, but gave some new insights on heat exchange and an offset hopper. Gasifier frame is bolted to the chassis.

Looking good! Will you be running Keith style preheat on this unit?

Hi DJ, Leave it to you to be the usual showman. It’s looking great. On my end, I can’t decide if my truck is more rotten than the gasifers or the other way around. Very frustrating working on this stuff in the salt belt. I’m busier than a one armed paper hanger right now with my land surveying business but I did get my truck out for a drive the other day. I think it is ready for our gathering in Indiana. It is about a 300 mile trip each way. I figure to do about 150 of them on wood. I sure don’t want to hold up any traffic on the 4 lanes like I did on my way back from Wayne’s a couple of years ago … I’m fighting off Lyme Disease again. That’s a barrel of laughs, not … Stay well, Mike LaRosa

Hello Mike,

My truck is actually very good. Few pinholes. It needs a repaint, but that is about all. It is now 5 years in the Netherlands. Guess it came from the South-west, since the dashboard is cracked. Vin number says it is build in Fremont California.


I have preheat, but not as excessive as Wayne has. I only exchange heat with ready gas. Primairy air enters the generator by the bottom, bumping into the hottest part of the generator. This is beneficial for both the primairy air and the ready gas, because the equilibrium is frozen.
I skipped the heat exchange aroud the reduction zone, like the Volvo has and like Wayne does. I think it is not a good idea to take heat from there, even when it is put back into the oxidation zone. My principle is: only use waste heat, insulate to the outside to keep this heat as long as possible inside, but also insulate the high level heat of oxidation and reduction zone. You see, 1300 degrees C in the oxidation zone and 500 degrees C of surrounding ready gas is still an 800 degree jump…

So much attention is put into hearth insulation and avoiding heat sinks. Middle section is Imbert/Mukunda style fuel preheat. Lower section and middle section get 25 mm Superwool insulation. The square top is the hopper/monorator and is of course exposed to ambient temperatures.


I find myself thinking in songs more and more recently. Your second bed cut picture 'minds me of the rock song lyric, “The first cut is the deepest”. Make’s you clench up doing the first cut on somthing rare, valued and still intact does it not? Then . . . once done; it truely is the old English saying of “In for a penny, in for a pound!” Then committed and “No going back now” it becomes easy to enlarge and expand in an efficient workmanship manner. I see this too in your second picture. Tree felling, animal butchering I feel the same way. Not that we don’t, or can’t do these. Just means we still retain something important not to lose.



That’s excact the way it went! First cut very lean. Hmm, tight fit. Bit wider; still tight. What the heck, floor plate has no strength anyway, cut wide enough and bolt the remaining wobbly floor to the gasifier frame!


Avoiding firetube meltdown?
Over the last year, and before Wayne “opened up” his hearth, I have been designing a similar unit. I arrived at a similar conclusion to yours, namely that one shouldn’t preheat air by taking heat off the reduction area of the firetube, and in fact, you shouldn’t use the heat off the wall of the combustion (nozzle) area of the firetube, either. Then, knowing this probably wasn’t lost on Wayne, I asked him about it. He answered that he had tried an insulated firetube, and had melted it down!

I know you build with stainless, which will help some, but even still, how do you avoid overheating the firetube?

Hello Martin,

The firetube itself is insulated by inert char and ash. The oxidation cone is made by this natural insulation, just like a V-hearth. In the reduction zone temperatures are a lot lower, so a stainless steel cone or cilinder will survive.

Long message short: insulate the firetube on the inside.


Right, we got a flare.

Everything looks good and feels good. When the outcoming gas reaches the 350 degree F mark, both flare size and the thundering roar from the gasifier become frightening. Not bad for a small hand held vacuumcleaner in push mode as a blower. Every gasifier growls more or less when it reaches working temperatures, but this one makes you feel it.

Next weeks the filterbox/aftercooler combination is to be build.


Hi DJ,
Beautiful work as per usual!
Those are the coolest looking Cyclones I have ever seen.

Beautiful work is right. Very tidy indeed, thankyou for sharing it.

Wow DJ, It looks like it belongs in the space program!