Carburetor Confusion! What's the Best Setup? | Engine Masters | MotorTrend

Street gearing and an automatic trans with a near stock converter: Vacuum secondaries. Everything else, double pumpers. I've been building carbs for 40 years.

What cracks me up is my buddies and me figured most of all this stuff , you guys talk about and test on all your shows. In the late 60s early 70s. All of use trying different things the hard way , racing each other, one step at a time. the drag strip times was our dynamometer. Really miss those times,we still talk about them, those of us still alive😢

I really, really love this series. Excellent, useful, rigorous info, presented directly and to-the-point. Well done.

Great job as always, just converted to a choke-less carburetor recently, glad to see, there should be a little bit of a gain!

I enjoy the stellar information and the banter. You guys are great.

Great information. I had those same questions and, I agree with your answers! The only other difference that you qualified in the beginning is, that (I.e.)a 750 carburetor would be the Minimum that carburetor would flow. It could actually flow much more in a given throttle body. Great job gentleman!!

Great show, I always enjoy it. Just started rebuilding my 850 double pumper from my 455 Firebird a couple of days ago ...

Great episode guys. Informative as always. Thanks.

I love this show, there needs to be more of it!

You guys have the best show hands down. Great information, knowledgeable hosts and very entertaining! Keep up the great work.

I’ve always been a fan of the tri-power setup.

That was a really useful & interesting comparison. Well done😊

Glad to see my predisposition validated!!!😁

First, your shows are so therapeutic! Thanks! Anyway, was wondering how much of a difference a drop-base air cleaner would have made in these tests...especially with the choke horn?!

Thanks You Guys. There is hope getting my 750 Vac secondary no Choke Horn w. Metering Plate/Jets to work better.

Great information! I have to of the same carbs one vacuum and one mechanical. I’m gonna put the mechanical on and try it out

What about comparison of the A/F curves between carbs? I was expecting to see that presented as the punchline.

Best series ever! I miss it from it was here on yt...

The test with and without a choke horn is not completely accurate. Both carbs would show improvement with a K&N stub-stack, but the same principle would apply with a proper air cleaner base on either carb. The truth is, if you add a wall entirely around the airhorn that forces the airflow to drop straight down into the airhorn instead of entering from around the sides (as with a flat or non-existent air cleaner base), then the airflow is both better in volume and in flow quality. You can see this principle with your sink at home. With water flowing around the drain from all directions, you will get a "vortex hole" in the middle of the drain's flow. If you force the flow to enter from above , it will eliminate the vortex and allow straight-line flow. We do this with the bottom of the carburetor when we add a spacer. It does not just improve performance strictly because of the added plenum volume that may be needed, but by forcing the air through the carburetor in a straight line for a longer section. The longer the air is flowing straight before and after the carburetor's venturis, the better the flow and volume will be. That is one reason why "tunnel-ram" intake manifolds actually do so well. If the only air cleaner that can fit on your carburetor due to hood clearance issues is a small (less than a 3" tall filter), then the carb with the milled off choke horn is going to work better only because it will allow more airflow into the engine, even though it is a less efficient airflow than optimum. If you can, use a stub stack and a filter element top lid for the best performance. Been there, done that many times. The other issue - double pumper vs vac secondary : the double pumper is better designed for performance engines with camshafts for RPM/HP. Once you cross over a certain cam duration (depends on many variables, but usually around 220 degrees) the engine needs fuel added to the airflow instantly to complement the instant airflow allowed by the rapid opening throttle blades. The double pumper is designed to do that and if tuned correctly is basically a mechanical fuel injection system in operation. Vacuum secondaries cannot do this. They are "reactive" to airflow and always lagging behind the airflow curve by design. Great for torque because they constantly "size" themselves just a little smaller than optimum cfm at all engine speed and load ranges. Just not able to give the engine that maximum airflow upon demand instantly as the DP carb can do.

Very informative. I'll always use carb. Had a van burn up because an o ring on injector leaked. You never know when they go.