art of the allure of traditional hot rodding lies in its utter simplicity. As my latest project takes to the road, it is time to deal with those pesky little details that make such a big difference. My ’36 Ford phaeton is pure vintage hot rodding. Super Bell I-beam up front, split bones, with a 9-inch rear on parallel leaves out back. Under the hood is a vintage ’47 59AB Flathead built with Sharp heads and intake sourced from the Flattie gurus at H&H Flathead. We even stayed with a 12V generator from a ’56 Ford mounted directly in front of a pair of Stromberg carburetors. The motor was built here in my home shop using ARP fasteners. The Stromberg electronic ignition fired the Flat motor to life on the first try … ah life is good.

Coupled to a T5 tranny we did a bit of local motoring; the occasional tailpipe popping made it clear the engine would need a bit of tuning. We returned home and allowed the motor to cool. One of the many joys of a Flathead is the spark plug access. Working on a cool motor, we pulled the plugs to discover the engine was running “rich” or “fat,” or whatever your favorite term for too much fuel and not enough air might be. Since we were running two brand-new Stromberg carbs, we decided to read the informative instruction booklet; it’s amazing what you find in a manufacturer’s instruction sheet. Before proceeding with the fine-tuning, the engine must be free of vacuum leaks and ignition problems, and the idle should be set at the desired rpm.

While twin carbs might be one too many for a basically stock engine, multiple carbs are simply mandatory equipment for any real hot rod, and with proper tuning they work perfectly. As per the instruction sheet, before making any adjustment, we disconnected the gas pedal linkage and the linkage rod connecting the two carburetors to ensure both throttle plates were closed.

Our first adjustment was moving the accelerator pump rod from the “W”-post to the “S”-post on the carburetor linkage arm. (Think “winter” and “summer.”) Moving this rod to “S” on both carbs provided a less-aggressive accelerator pump. This is our first step to curing the “rich” fuel situation.

We began our next adjustments with the air/fuel mixture screws on the rear carburetor. Like most carburetors, these screws are turned clockwise to restrict fuel flow and lean the motor out and turned counterclockwise to add additional fuel and richen the motor. Adjusting involves turning the knurled air/fuel circuit screws in (clockwise) until the engine stumbles, then slowly (seriously, do this slowly, one-quarter turn and pause) turn the screw back out (counterclockwise) until the engine runs smooth. You may notice increased rpm when the air/fuel hits that “sweet spot.” Now move over to the second adjustment screw on the rear carburetor and repeat this procedure. You should already notice an improved idle.

We moved to the forward carburetor and repeated the same procedure: turn ’em into a stumble, turn ’em out until it’s happy (smooth). Moving the throttle by hand showed us the engine ran smoothly through the range to 2,500 rpm. If these adjustments have altered the idle, adjust it now by turning both carburetor idle screws in equal amounts to attain the desired idle. We were so pleased with how the Stromberg carbs responded to our adjustments that we almost closed the hood, thinking we were done.

Then, a friend who works on some of those “furrin’ cars” mentioned synchronizing the carburetors, also known as flow balancing. This is critical on engines with carburetors feeding opposing banks of cylinders mounted on separate intake manifolds. Since our inline carburetors fill a common plenum, the flow may not seem as important, but since we were in the full tune-up mode, we decided to go with the flow and see if it really changed anything.

The first step was buying a flowmeter. You will be pleasantly surprised to discover that your basic Rage or “snail-style” flowmeter is very affordable, at around $35. Armed with our new tool, we warmed the engine to normal operating temperature. Next, we removed our cool Edmunds Custom air breathers from both carburetors. The throttle linkage from the gas pedal to the carburetors and the linkage connecting the two carburetors were disconnected. This ensures both carburetor throttle plates are in full closed position and the linkage is not affecting the carburetors in any way. Our Strombergs are connected with straight linkage so there are no concerns about tuning progressive linkage.

Before restarting the engine, we tested the fit of the flowmeter to our Stromberg carbs. The tapered cone was way too small for the carburetor opening. We made a simple adapter out of flared exhaust tubing and a piece of radiator hose. This adapter sat perfectly on the carburetor lip, and the tapered flowmeter sealed nicely inside the flared tubing. Problem solved, although it should be mentioned that adapters are commercially available for the flowmeter.

We fired the engine, held the flowmeter on top of the rear carburetor, and took a reading. Now, we will confess we aren’t exactly sure what the meter numbers mean, but we do know we want the exact same number from both carburetors. We made a note of the reading and then tested the front carburetor and noticed that the carburetor was flowing a good bit less air than the rear carburetor. With the flowmeter back on the rear carb, we backed the idle speed screw out (counterclockwise); this lowered the airflow in the rear carburetor to a number closer to the front carb. It also lowered the idle. Next, we moved the flowmeter to the front carburetor and turned that idle speed screw in (clockwise) to raise the idle a bit, thereby increasing the airflow to match the front carburetor. We went back and forth several times until we had the flow exactly the same on both carburetors.

We checked our idle speed and found it was a bit high. Once again, we synchronized the carburetors with the flowmeter as we lowered the idle speed. This was achieved by adjusting both carburetor idle screws until we had the desired idle along with perfectly matched flow. Ultimately, our Flathead idled smoothly at 600 rpm with perfectly synchronized carburetors. Next, we carefully adjusted the linkage rod to connect the two carburetors. We checked the flow to be sure the rod had not affected our airflow. Then, the throttle was connected back to the gas pedal, air filters were installed, and it was time for a testdrive. We were amazed at how smoothly the engine ran through the rpm range. There was no “flat spot,” no tailpipe popping, just raw, unbridled Flathead power.

So, our verdict is in: This was definitely worth doing. While the engine ran well after adjusting the air/fuel settings, synchronizing the airflow between the two carburetors brought it to the next level. And the best part is the process of getting there is actually fun. Airflow should be checked anytime you change idle or make carburetor adjustments.

We recommend leaving the airflow meter/adapter in clear view around the shop. When folks ask, “What’s that for?” casually mention … “Oh, that … I use it when I’m synchronizing multiple carburetor setups” and watch the eyebrows go up.