Dyno Testing Carbs vs a Very Unique EFI Setup

Recently Keith Dorton of Automotive Specialists built two very similar engines. They were, in fact, practically identical except for the induction. Both were 400 cubic inch small block Chevy's with identical Molnar stroker crank and rods, Crane Cams valvetrain, and AFR cylinder heads.

The difference between the two was the induction systems. One was outfitted with an Edelbrock single-plane Victor Jr. intake manifold and a Holley carburetor, while the second got its air and fuel from a very unique Borla Induction EFI setup controlled by a FAST ECU.

This ins't exactly an apples-to-apples comparison, since we are using entire different systems. In fact, the big-inch Chevy could almost certainly use bigger throttle bodies on the EFI setup to make maximum power. But the dyno testing is pretty interesting, and we always love any opportunity to make a little horsepower.

 

 

Everything on our two test engines are identical except for the induction and ignition systems. Engine builder Keith Dorton begins with a Dart SHP block and stroker Molnar forged crankshaft. The connecting rods are also from Molnar.

 

Coated Mahle pistons with a slight dish provide a floor to the combustion chambers.

 

The camshaft is a billet roller piece from Crane. It is ground with 236/244 duration at 0.050 lift.

 

The CNC-cut AFR heads are topped with 1.5:1 Crane aluminum roller rockers and PAC valve springs.

 

We tested with two different carburetors. The first is a 750 cfm Holley Brawler carb (shown). We followed that up with and 830 cfm Holley double pumper. The big-inch engine liked the additional flow of the 830 carb.

 

Here is the carburetor comparison. The green and purple lines are torque and horsepower for the 830 carb.

 

Next, we installed this four-deuce EFI setup from Borla Induction. This is not one of their Chevy-specific kits, but actually an EFI replacement for old Ferrari and Maserati carburetors.

 

Here's a look at the unique intake maniold for the EFI setup. We can't tell you who manufactured this intake, it was a swap-meet find and there are no markings on it.

 

We went with an MSD cam position sensor because it works well with the FAST ECU. Plus, the intake manifold's design wouldn't allow even a small-cap distributor to fit in the distributor hole.

 

With everything hooked up, it is dyno time.

 

Dorton discovered that the protective screens may have inhibited airflow -- and power. So, of course, they had to come off.

 

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