By Hobey Landrith
Matching just the right carb to your engine might sound straight-forward, and in fact most decently built engines will run on a poorly selected and/or badly tuned carb, though at a fraction of the performance they’re capable of. But getting it right, and I mean really right for a high performance application, is not a total slam dunk.
I had gone through a hair tearing experience years ago in trying to get an aftermarket carb to function well on a moderately high performance motor. After spending over $300 for the unit, and going through every adjustment available, including ignition timing and valves, I finally had to be satisfied with it’s burping, spitting and ever-present flat spot.
I did not want to experience that again, and so I contacted Don Gardyne of DG Motorsports (650-722-4795).
I presented him with a decent Holley 600 cfm core, gave him my cam specs and the intended use of the car, and he set to work.
Don specializes in custom applications, vintage race, street performance and rare Holley and Demon carburetors. He has over fifteen years of experience gained from trial and error testing and tuning in all sorts of performance vehicles in the real world environment they are used in. He does not just build the carb, hand it to you, and collect a check. He makes house calls, dials the carb in at both dyno and in-car events, and optimizes the set up and tune.
The 600 he built for me had modifications made to the idle, main metering and power enrichment circuits.
The idle circuit has had its fuel jet placed above the fuel level, which prevents the fuel from forming a puddle on the downward side of the idle well. This nets a smoother and leaner idle mixture that every engine responds well to. The secondary side of the carb is also fully adjustable for both idle speed and mixture volume. In addition, the secondary mixture screws feed air/fuel emulsion to the center of the intake manifold, which reduces that chance of fuel starvation in the center four cylinders at low engine speed.
The main circuit has had an additional emulsion hole machined in the metering block. This makes for a much more energetic air/fuel mixture available for the engine to burn, thus more power for the same amount of fuel volume in the intake charge.
The result is a very responsive 630 cfm carburetor that has been set up to perform specifically with my displacement, intake manifold, cylinder head and cam specs.
When Don walked into Cal Dyno on August 20th, he installed the carb, checked float levels and idle mixture volume, then we started and tested the engine. There were no jet changes required, the motor ran great, and after a short bit of fine tuning at idle, the day was done.
But, Don pointed out, there was still in-car test drive and tuning needed. That would bring the last and best out of the unit, and he’d be happy to do that, as long as it was local.
“Oh gee,” I said, “That’s a hard decision…yeah, I guess I’ll give you a call when it’s in the car so you can come over and we’ll make it perfect,” and all the while I’m thinking: is this guy an alien? Who does this? Answer: Don Gardyne
So what would you expect to pay for a tuner carb, and an induction doctor that makes house calls and is available for phone consulting as well? I had spent $300 years ago for a unit that was never quite right, and yes this is more, but believe me, not much more. And considering what you are getting, it is a bargain.