Category: Carburetor

Bennett is now rocking fuel injection on Mr. Hanky, so he figured he’d ditch all the 40-year-old technology sitting in his garage. As we were beginning to wrap up with the project last week he walked out of the garage and handed me a spare Thermoquad he had sitting on a shelf somewhere. “I’m not going to need it,” he said confidently.

I put it on the bench this evening and looked it over in comparison to the known good International carb I’ve got already. The new one has a bunch of gewgaws and linkages and levers hanging off the body that I’m not familiar with; that’s because it was built for a 1979 California-market Chrysler 360 with an automatic transmission.

For comparison: the one on the right is a carb manufactured for International Harvester. The new one is in pretty good shape, so as a spare it’ll be good for spare parts. I realize at this point I just need to accept that I’m not going to finish the carb I’ve got and call the guy I met who rebuilds carbs for the  International dealer up the street.

One of the challenges and quirks of driving 50-year-old vehicle is that we are slaves to the fickle black magic of carburetion. Many carburetors before the 1970’s were simple devices with few moving parts, but as emissions and fuel economy standards were implemented by the government, engineers added all kinds of hoses and vacuum lines and secondary linkages on carburetors to eke every last molecule of economy out of them while they scrambled to update their ancient engine designs. My carburetor is one of the last evolutions of this need for economy and power: a Thermoquad, which looks like R2-D2 barfed up a mechanical hairball.

Electronic fuel injection finally came of age in the 1980s and made the mechanical complexities of carburetors obsolete. As carbureted engines are increasingly rare on the road, it’s getting harder to find mechanics who know how they work and what to do with them. It’s also a pain in the ass to get a carbureted engine started after a week of sitting.

So it’s with great interest that I’m headed to Bennett’s this weekend to help him install EFI on his Scout. He bought a premade kit from Hamilton Fuel Injection—the manufacturer whose tech seminar we attended at Nationals this year. It’s pricy to buy outright, but his reviews are impeccable and he tailors each kit to a specific IH engine, as well as helps tune the unit after it’s installed. I’m very curious to see how easy it goes in, and as I mentioned before, I’m seriously considering it as an upgrade to my engine.

Brian and I are also going to hit the junkyard to see if we can find an electric steering pump for his Scout, which came with manual steering from the factory. It’s been a long time since I’ve walked the rows at Crazy Ray’s so I’m looking forward to the day with anticipation.

So all three main sections of Good Carb are washed and drying on the bench. I dunked them each in Simple Green for a couple of days and then scrubbed them with a toothbrush, and 99% of the crud came right off. After a rinse with warm water, they look close to brand new. I’m going to let them dry completely and then start tearing down and replacing parts next week.

When I was a kid, I spent countless hours of my life building with LEGOs on the floor of the family room. I’d build something, take it halfway apart, put it back together again, and then repeat that cycle until I got it just the way I wanted it. All of this was unwitting practice for my adult life, where I’ve disassembled computers, electronics, power tools, engine parts, and other assorted machines without fear of being unable to re-assemble them.

So, working my way through the videos I’ve downloaded, I decided I’d start disassembling the dirty unit first to get my practice in.

Most of the linkage came off relatively easily, and when I understood the secret Thermoquad disassembly trick (two hidden screws under the primary butterfly) the whole thing came apart pretty easily. It was then when I understood why it was so filthy. At some point it had gotten a lungful of water or mud, because both chambers were full of brown crud. The underside of the resin bowl was filled with corrosion and blackened carbon. I began to get nervous, thinking I’d never get it cleaned up.

Into a bucket of concentrated Simple Green it went, and after about an hour’s soak the resin bowl came out looking brand new. I scrubbed it with a toothbrush and bottle cleaner to get the residue out, and let it dry on the bench.

Then I threw the top air horn in to let that soak. Corrosion had crusted over everything made of ferrous metal; the float arms were rusted solid. The whole thing looked charred and sooty. I figured I’d try the detergent to see how clean it would get first.

After about two hours I was shocked to find it had turned Simple Green to Simple Brown, and most of the soot had disappeared. The aluminum appeared much cleaner, and the metal parts were more visible.

It’s still pretty fucked up, though; Simple Brown can’t dissolve whatever that white crusty stuff is in the upper left, and the well under the float (that black square thing on the left) is filled with it. It’s going to soak overnight, and then if I can’t get the parts free I’ll put on some gloves, take it outside, and hit it with the carb cleaner.