I think the technical term is Wasted Spark. Might be more helpful to see if your Volvo engine is designed with that sort.
It’s why I wouldn’t be comfortable putting a gasifier on a Harley Davidson I know that’s for sure.
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Cody, of course. I’m old enough to sometimes forget it’s possible to google and find out right away 
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Don’t have to be old to have Brain Farts, I have moments of thoughtlessness all the time. It’s like my brain has horse blinders on and I can only see what’s right in front of me, metaphorically speaking.
I’m from the last generation when you just asked someone instead of searching it up, and I often forget I have a supercomputer in my side pocket.
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Found it right away. The Volvo doesn’t have a wasted spark system.
I may have to just wait for some soot to seal my valve seats properly 
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Hi guys, Just stopped in for 11 minutes, the time it says should take me to read about the new Swedish hot-rod. Congratulations JO on the new build. If you look back I think I posted pictures of my last build. It was similar to your fire tube— 10 in. dia tube, woth 10holes drilled near the top of the tube. Then about 10 - 12 in. below was a restriction— don’t remember the dia. but about 6-7 in dia. opening. The grate was just the bottom of my ash pit. I only drove the truck about 8 mi. and it ran like a race horse on stairodes. Buutttt! I got tar in the throttle. When I took it apart, I could see metal failure around my nozzle holes. I guess those are stainless plates lined around the inside of your fote tube. Are those nozzles on your stainless.
I’m glad to hear you are getting exceptional power out of this kind of modifided WK design. I suspected I got much better performance with that last build, but too few miles to be sire and never could get my speed-o to work. Can’t wait to see a sketch of your system by our friend from South America (can’t remember names) I’m not sure I am able to quite vision your build.
As usial I’ve talked to long. Hope to see more pictires and vidios. TomC
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Tom, good to hear from you. Have you been working on your gasifer?
From all your questions that you has asked others I have learned so much. Hope to hear from you more.
Bob
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Real good to hear from you Mr. Tom 
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Wow! Tom, where have you been all this time? We hollered and waved. Busy lawn-mowing? Playing with your new tractor and bucket?
Yes, ss heatshields and ss protruding nozzles, but only 4" dia restriction. I made some tar too, on the maiden ride, but it seems nothing reached all the way up front. Not even a haze at lightup ever since.
Really glad to hear from you. We would all like to hear what you’ve been up to.
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Good to hear you are still with us Tom, l was begining to worry!
JO, indeed my brain is begining to get all soggy from time to time, but you know how it goes… Nightshifts…
It was the same with my Mercedes. However l seem to remember backfires were worse when the mix was too lean.
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Here is good thing about your Volvo, it should never have heavy carbon build up like on your truck. The back fires will keep it cleared up. Lol. Are your back fires really loud or they like a fart or woosh?
I only have them if I have my foot all the way down on the gas pedel clumbing a hill pushing 4000 rpms plus. As I let off the gas pedel I will get a hopper puff, sometimes or a intake puff. The two tennis ball valves under the hood handle it.
When I had the intake pentium leak it was happening a lot when I would accelerate. The new heavy duty aluminium pentium one sealed the intake up and no problems.
When the intake manifold was removed and opened up to put the new aluminum pentium on the intake passage ways were half way closed off with carbon build up. It had to be chipped and chisel to get the carbon build up out of the intake. I now burn my intake out more often. I do not want to have to do that again. If I would of had a smoke intake fire incidence it would of burned for a long time. It never happen even when trying to manually burn it out. Maintenance, maintenance, and more maintenance, is very good.
Bob
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Yes Kristijan, you are right , the lean burning fuel was always the case with my backfires. Never had it happen with a rich burning fuel.
Bob
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Hm…backfires are all new to me.
Maybe idling for a while and then a sudden acceleration throws the mix off a little. Also this motor has a separate iac, by-passing the tb with pure air straight from the breather. I did block it with an old style tap valve, but I will have to check if it seals properly.
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Pretty loud actually. Sounds like I hit somthing. Even with a puffer valve on the mixer and one more on the slingshot, I bent the new homemade metal butterflies.
I haven’t tried 4,000 rpm yet 
but it sounds like you have opposite problems. Running hard at 3,000 rpm doesn’t cause my backfires, nor does letting the pedal up. Returning to light throttle after idle position does. You heard my first ever pop, didn’t you? Sharp bend to the left at idle, and then a light throttle to start moving into the parking lot - POP!
Funny you mention soot. I’m at 150-200 miles and judging from my previous builds I should start having a little buildup. But nothing yet. Still all clean downstream the filter. Maybe you’re right, the backfires clear it up
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Im surpriced with every post how similar our cars performed JO. Amazing.
Here is what l think hapened to me and you now.
When the pedal is relaxed, there is only a small amount of gas drawn trugh the supply pipes. Vacuum in the manifold is high. When suddenly you want power and step on it fast, all that vacuum is released but since the gas has a lot of inertia in supply pipe and cooler, there is momentairly mostly air drawn in trugh the air valve as it has almost no inertia. The engine sucks this lean slow burning mix, wich still burns when the intake valve opens. In the meantime, the inertia of gas was overtaken and good mix is pouring in. The fire and the rich gas mix meet and off goes the filter lid (in my Mercedes case )
If my theory is true, there is a way to fix this even if timing advance is limited. One just need to make the gas supply line lenght and volume mach the air supply line lenght and volume. This way the inertia of the gas and air will be the same.
That, or build the valves super strong (ball valves, all welded) and accelerate like a sissy like l did on the mb
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I was just thinking maybe this is why Wayne’s v10 so rarely pops is the engine is having to draw a distance of pipe to get fresh air through a fairly restrictive paper style air cleaner slowing down the inertia of air movement making more engine vacuum pull through the gas lines…this may change my air mixer setup, I was planning for high flow filters maybe 5" off the mixer body
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Marcus, usualy with enaugh timing advance there is no problem. You wount even notice the thing. But both JOs Volvo and my Mercedes only had a 6deg window of advance, too litle for what we need.
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I hope that the Computer in my Buick will advance naturally. I don’t know personally of any way to advance timing with a 1998 Model.
But then again Mike LaRosa said he liked his Post-OBD2 builds.
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On my 95 F250 with a 7.5 liter engine I have never had an intake bang.
I normally keep the timing advanced 20 deg and the OBD1 system has a 25 degree advance for up to 45 total on a lead foot launch.
But I have learned to “drive miss Daisey” because of the poor gas quality after a idle downhill or a stop light.
I have 3” steel lines with poorly fitting butterfly valves for air and gas to the stock throttle body.
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Hi jan-O/ Just checking too see if you have done a thorough AIR leak test pumping smoke through all your system, Or if you think posible your seal ware burn tube seats in outer barrel could have over heated its seal before the charbed was built up . Just possible thought check, i welded mine ware burn tube sits on top barrel flange for the burn tube.SWEM/or Happy DOW Man. And good luck finding a timeing Modifications, That might be the problem too, THANKS for posting Your excellent build in progress.
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This might be one of the reasons why Wayne ran two 2" wood gas pipes up the the engine compartment to the mixing box with lots of mass flow with both valve open. Air valves only partly close down. Also lot of back up reserve gas in the lower gasifer, drop box, condensation tank, hayfilter, cooling rails, and other piping.
Bob
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