We hot rodders are a lazy lot. We're always looking for ways to make things easier. In the movie Two Lane Blacktop, the late Beach Boys drummer Dennis Wilson played a mechanic who spent the entire movie changing jets in the twin Holley carburetors of a big-block-powered '55 Chevy. If he had had a set of Brad Urban's Carburetor Shop Speed Blocks, he might have had more time to go after the girl in the movie.
For the rest of us, Holley carburetor jet changes are a fact of life. You drain the fuel from the float bowl (spilling fuel all over your intake manifold), remove the bowl, change the jets, replace the bowl and then replay the routine for the secondary side. If you're exceptionally gifted, the gaskets tear and you spend half an hour scraping gaskets off the bowl and the metering block. If you haven't been through this drill a few dozen times, don't count yourself as a true hot rodder.
Brad Urban has probably changed more carburetor jets than the rest of us combined. After a few thousand repeats of this brain-numbing procedure, he began to think there had to be a better way. Enlisting the help of compatriot Louie Hammel, the two developed the Speed Block, a fully CNC-machined aluminum metering block that duplicates a standard Holley metering block, but with a high-speed twist
Instead of mounting the jet in the metering block, Hammel created a brass cartridge that screws in from the top of the block. The bottom of the cartridge holds the jet in place inside the metering block in roughly the same location as the original Holley design. The beauty of this is that the cartridge can be removed from the Speed Block without removing the float bowl. This makes for incredibly quick jet changes.
Now you no longer have to drain the float bowl to make jet changes, which also means no more spilled fuel over a hot intake manifold. This dramatically reduces the risk of fire.
Taking this one step further, it's possible to change the jets in the carburetor even when the engine is running. Since the idle feed restriction limits the amount of fuel delivered to the idle circuit, there's no change to idle quality if you remove the jet cartridge from the Speed Block while the engine is running. We've tried this on a couple of cars, and it works just as Urban claims. Now that we've played with the Speed Blocks, we're definitely spoiled. We'll certainly never do another dyno test without them.
Over the years, Holley has created several different metering blocks for the 2300 two-bbl, 4150 four-bbl, 4160 four-bbl and Dominator Holley carburetors. Speed Blocks are available for all these applications, including alcohol carbs. You can even use a primary metering Speed Block on the secondary side of any Holley for four-hole idle control with a modification to the throttle plates that Brad Urban's Carburetor Shop can perform for you. The Speed Blocks retail for slightly less than $100 each.
For drag racers, circle burners or street enthusiasts who are looking for ways to make their lives simpler, the new Speed Blocks are the quick-change ticket for any Holley carburetor.
