Reader Question: The 4BBL vs. TBI?

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Here’s the latest reader question, along with my reply!

Ed asks:  I’ve read your tributes to the carburetor and get the emotional appeal but for those of us who aren’t adept at tuning and adjusting a carburetor, having one is a real deterrent to owning a nanny-free older car. What do you think about replacing an old car’s carb with a throttle body fuel injection system?

My reply: I think, as Gomez used to say, that it’s a capital idea! TBI is very simple; analogous to a jet engine vs. a piston engine. But not as complex as a modern high-bypass turbofan engine.

TBI system don’t require re-engineering the engine. The “stand alone” aftermarket units are designed to bolt to the intake manifold that the carb used to sit on. The only other significant change is replacing the mechanical fuel pump with an electric one – but that’s easy and cheap, too. An oxygen sensor in the exhaust system may also be needed but – again – not a big deal or an expensive one.

Once installed and set up (many have self-learning capability and will tailor the air-fuel ratio just so, for your engine)  these TBI systems usually run forever – decades – with no adjustment needed. Just keep ’em clean.

The downside is the initial cost – vs. a carb. A TBI kit will cost you about $1,000 or so (depending on the make/model/application) and if you have to pay someone to do the install, figure another $500 or so for that.

This would pay for a lot of carburetor tune-ups and rebuilds – though I admit you can’t put a price on not having to deal with taking it in for adjustment and just driving your car. You’ll also usually get faster warm-up and crisper throttle response with the TBI and may even see a noticeable uptick in gas mileage.

So, you’ll have to weight the costs – vs. the advantages.

Also, be sure you keep the carb! I mean, keep it in a box somewhere. Because someday, you may decide to sell the car and it’ll be worth more if you still have the parts it came with!

. . .

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  1. I go along with multiple point fuel injection anyday. Simpler, more reliable, faster starts, no hesitations, and a helluva lot less mechanical repairs. I’ve had both, started driving in 1969.

  2. I’ve owned several vehicles with Q-jets and drove them for decades. I never had to adjust or do a dang thing to any of them except change that stupid little fuel filter, and that is from 13,000′ ASL to down to the Gulf of Mexico. You do need to run a clean air filter, especially at high altitudes.

    Only Q-jet I ever had rebuilt was one I got from a junkyard to replace a POS Holley on a used pickup that I had bought. In retrospect, I probably should have just slapped the junkyard carb right on and see how it worked. I had a neighbor who was a state mechanic rebuild it for me for, I think $100 in 1996.

    The automatic chokes can be a pain. The TBI is certainly a lot better to just start up and go in most weather, but in extreme cold a carb with a good working choke is more reliable to start within the crank time of the battery.

    I definitely prefer the TBI to the Q-jet (to everything, actually!) but I don’t see it being worth the expense and time to change it over. Since I never in 40 years of running them touched a Q-jet (except for choke and filters), I reckon most of the problem is someone monkeying with it and never getting it right again.


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