Best Carb For Shovelhead
Article by Vintage Vinny
One of the more popular upgrades for Shovelheads is a performance carburetor. A few of the original factory carbs are still suitable, but not all are still available.
This article reviews Big-Twin factory carbs from 1966 through 1984, plus several aftermarket replacements.
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Shovelhead Carbs Through The Years
First-year models (1966) were fitted with a Linkert DC7 carburetor. It's a simple design with only two moving parts - the float assembly and throttle shaft.
The Linkert DC carb is not a first choice for added performance. But if you've got one, it's rare and valuable, and you may just want to run it.
A switch to Tillotson was seen in 1967.
Due to it's complexity, the Tillotson was not appreciated in its day. Lack of knowledge and poor parts availability tarnished their reputation, but when set up correctly, they work fine.
Both the Linkert and Tillotson are long discontinued, and finding parts or having service done to them can be difficult.
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Bendix Carbs
From 1971 through 1975, FL and FLH models left the factory with a Bendix carburetor.
Harley FX and FXE models were fitted with a Bendix carburetor from 1971 through 1975.
On non-modified 74ci Big-Twins, a 38mm Bendix is still a good carb choice. It will allow easy starting and moderate performance.
Shop: 38mm Bendix Carb for Shovelhead
Bendix 38mm vs 40mm
On larger Big-Twin motors, including factory 80ci engines, greater performance will be seen with a 40mm Bendix.
Shop: 40mm Bendix Carb for Shovelhead
Both the 38mm and 40mm are compact units, so they sit "tucked in" and allow you to run almost any type of air filter.
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Keihin CV Carburetor
In 1974, Harley FL Touring models switched from Bendix carburetors to Keihin, while the FX models continued using the Bendix carb.
The Keihin carb is a slide-type, or CV (constant velocity) carburetor. It was not popular in it's day, mostly because it was made in Japan. But over the years, it's slowly became accepted for what it is; a decent, inexpensive carburetor.
Like all slide-type carburetors, the Keihin gives smooth power throughout the RPM range. The CV-40 is a popular choice for an 80" Shovel.
NOTE: Harley models originally equipped with Keihin carbs will have the bar and shield and 'Harley-Davidson' stamped on it.
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S&S Super E
The prevailing favorite replacement carburetor brand for Harley Big Twins is S&S. The Super E has a 1-7/8" bore, slightly smaller than the Super G, making it suitable for engines with displacements up to 100 cubic inches.
Shop: Super E for Shovelhead
Right out of the box, a Super E will pull harder and the engine will rev easier. While highway riding, your motor will want to rev faster and higher.
Push-Pull Throttle Cable
Starting in 1981, Harley V-Twins had a double (push-pull) accelerator cable. This was to help prevent accidental throttle sticking.
The Super E carb requires the use of a dual cable throttle, one push and one pull.
If your bike is not equipped with dual throttle cables, you can buy them here.
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Mikuni Carburetor
The Mikuni is also a slide-type carburetor. On a stock or slightly-modified motor, a VM38 or VM40 Mikuni is a good choice for a 74 or 80 Shovel.
Made for Harley Big-Twins, Mikuni claims a 25% power and torque increase when you bolt on an HSR42 Smooth Bore Carburetor.
NOTE: Rocker boxes and oil crossover lines sometimes interfere when installing a Mikuni. Fitting one with fatbob tanks may also be an issue.
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Lectron HDX
If price is not an issue, consider a Lectron Billetron HD-X. Yes, they're actually made of 6061 Billet aluminum, and have no jets or needles. There is a 'tick-over' screw and a metering rod, so set up can be done in minutes.
Big-Twin owners who have installed Lectron carburetors say they saw substantial power gains with better gas mileage, plus easier starting.
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Screaming Eagle
Based on the Keihin unit, the Screaming Eagle 44mm CV carburetor was designed for use for 1984 through 1999 1340 Evo engines and 1999 and later Twin Cam 88 engines. We don't know of anyone who has, but it can likely be adapted for Shovelhead use. They may just need a slight jetting change.
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Edelbrock Quicksilver 2
These are no longer made, and parts are becoming scarce. So unless you already have one, these are not a first choice for carb replacement.
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Back In The Day (SU Carb)
There is a big difference between what was available 60 years ago, and what's made and sold today.
The SU was one of the first constant velocity (CV) carbs to be adapted to Big Twins, and was a popular swap for Panheads and Shovelheads in the sixties and seventies. These are variable-venturi carbs that were originally found on European cars, such as Triumph, MG, Volvo, and others.
Measured by bore size, common SU carbs are the HS2 (1.25"), HS4 (1.5"), and HS6 (1.75").
Because many classic cars were fitted with SU carbs, air filters are still available. You could also modify existing air filters to fit the odd 4-bolt pattern on the SU carb. This involves measuring and drilling additional holes in the backing plate.
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Manifold Gasket Seals
A Harley Big-Twin carburetor vibrates quite a bit while running, which may lead to cracked intake seals, vacuum leaks, and rough running.
Pictured, cracked intake seal.
James Gasket offers an intake manifold and gasket kit that you can buy here.
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Carb Bracket
A carburetor support bracket is a good idea for any V-Twin motor.
You can buy a carb bracket, but they're fairly easy to make if you have a good solid bench vice and a drill press. The one in the picture was made from a metal shelf bracket.
Read: 7 Drill Press Uses For Motorcycle Repair
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Conclusion
Whatever you decide to run, install a gas filter, such as this mini glass bowl fuel filter from Milwaukee Twins.
It's equally important to have a good air filter, the bigger the better. And resist the temptation to run a velocity stack. Yes, they're cool looking, but they allow dirt and dust to get into your engine.
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