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| The 4-hour spacer introduced a stronger signal to the carb, sometimes making it work better… | …but, sometimes that stronger signal made the carb pull too much fuel and the engine again lost power. The solution was to start off with 4-holes on top and open up the spacer on the bottom. |
 Then the spacers evolved further with CNC-machined taper of the venturi holes. This further improved signal and spacer response. |
Averaged Torque Tells the Tale
Here are the average and peak numbers generated by a healthy 406ci pump-gas small- block on the Hardcore Horsepower dynamometer. Keep in mind that I changed nothing else in each test. I just bolted on another spacer and let ‘er rip.
| Spacer | Avg TQ |
Peak TQ |
| 1.0-inch open | 493 |
526 |
| 1.0-inch 4-to-1 | 495 |
527 |
| 1.5-inch 4-to-1 | 496 |
528 |
| 2.0-inch 4-to-1 | 497 |
530 |
Note how torque crept up as the spacers became taller? Well, there’s a point of no return here and had I kept going higher, the torque would’ve fallen off. But this clearly illustrates how the motor liked having the enlarged plenum area and lengthened carb venturi created by the 4-into-1 spacers.
Perhaps the final evolution of the spacer came with new plastics designed to take high heat and still perform.
There are many different sizes, shapes, and materials of carb spacers out there, and no one particular model works best on every engine. And, to make things even more frustrating, not all of them will fit under your hood.