National Dragster Article on
The HVH "Super Sucker" carburetor spacers

Reprinted with permission from National Dragster http://www.nhra.com/

Race Tech article: New-age Carb Spacers

A couple of years ago, I wrote a column on carburetor spacers in which I discussed how spacers worked, how they can be used to tune a given combination, and what materials are used in spacer construction. From my experience and from what most racers already know, there usually isn't much power in a spacer. Oh, you might find a horsepower or two in some cases, and you can move the power band around a bit and help distribution in other cases, but for the most part, there isn't much extra grunt available from a spacer, or is there?

 

    

Fast forward a few months to the 1999 PRI Show. Joe Petelle of HVH was manning a little piece of a booth shared with his pals from Porta-Tree. The folks in the booth handed me a one-inch-tall carb spacer with the simple words "Try it."

Joe Petelle and his son, Keith, own HVH, or High Velocity Heads. HVH may not be well known in drag racing, but it's another story in Winston Cup, where they ported heads and manifolds for Chevy and Ford teams from 1980 to 1992. In addition, HVH designed a series of intake manifolds for Brodix and created the layout for the Canfield big-block Chevrolet head. Currently, they primarily build carb spacers, but they also do limited amounts of custom work for short-track applications and drag race cars (yes, they work on NHRA Stockers, iron heads, and basically anything that flows air).

The HVH Super Sucker that I picked up at the PRI Show languished on my desk for months before it was moved to my work bench, where it languished for many more months. Finally, I slipped it into my camera bag on a trip to Speed Way Testing in Richmond, B.C.

While talking to John Heida of Speed Way Testing about his SF901 Dyno installation (a rather nice installation, by the way), I opened my camera bag and tossed the spacer to John with the simple instructions "Try it."

Heida knows his way around cylinder-head and manifold flow, and we scrutinized the Super Sucker. Sure, it was made from a very composite material, and it was a one-inch-tall version. And, yes, the top side (carburetor mount side) looked like any other four-hole spacer for a standard Holley flange. But the bottom (intake manifold side) was far different than anything we had seen before. I think independently we came up with the same assessment: It's different, but it's a carb spacer. It might be worth a horsepower or two. It's probably nothing more than a tuning aid.

Nothing more came from all this until a few days ago, when the fax machine in my office began spewing paper. Out came a couple of dyno-pull results from Speed Way Testing. The results from those tests were remarkable.

The engine in question was a relatively mild 355-cid small-block Chevy with a set of small-valve heads that Heida had reworked. If you check the engine's volumetric efficiency against the brake specific, you'll find that the engine is a pretty efficient piece. Data was corrected for 29.92 inches Hg, 60-degree F dry air. The tests were done in a conventional A-B-A format (for the sake of simplicity, I haven't included the final backup test; it matches the first test exactly). Here are the baseline test results:

 

rpm	torque horsepower	volumetric efficiency	brake-specific	fuel consumption
5,000	402.8	383.5	104.4	.49
5,100	401.8	390.2	105.3	.49
5,200	397.3	393.4	105.2	.49
5,300	400.6	404.3	105.4	.49
5,400	393.7	404.8	104.9	.49
5,500	390.0	408.4	104.4	.49
5,600	386.2	411.8	103.1	.52
5,700	380.6	413.1	103.0	.51
5,800	375.6	414.8	103.2	.51
5,900	376.2	422.6	103.1	.50
6,000	370.7	423.5	102.8	.52
6,100	366.4	425.6	102.7	.50
6,200	362.8	428.3	103.2	.51
6,300	359.3	431.0	102.4	.52
6,400	352.8	429.9	101.6	.52
6,500	349.4	432.4	101.4	.53

Peak in baseline configuration was 432.4 horsepower at 6,500 rpm.
Maximum torque was 402.8 foot-pounds at 5,000 rpm.

The second test duplicated the first with only the one-inch-tall HVH Super Sucker carburetor spacer added. Results follow:

 

rpm	torque horsepower	volumetric efficiency	brake-specific	fuel consumption
5,000	413.2	393.4	105.0	.48
5,100	405.3	393.6	104.7	.49
5,200	398.8	394.9	104.1	.50
5,300	402.1	405.8	104.6	.50
5,400	396.9	408.1	104.4	.49
5,500	390.4	408.8	104.5	.50
5,600	387.2	412.9	103.7	.50
5,700	379.8	412.2	102.9	.50
5,800	377.1	416.4	102.7	.51
5,900	378.6	425.3	102.8	.50
6,000	372.6	425.7	102.4	.50
6,100	370.9	430.8	102.4	.49
6,200	369.0	435.6	102.7	.51
6,300	367.3	440.6	102.6	.52
6,400	367.1	447.3	101.4	.51
6,500	353.7	437.7	100.7	.52

As you can see, the small-block peaked at 447.3 horsepower at 6,400 rpm, and the maximum torque of 413.2 foot-pounds occurred at 5,000 rpm. In comparing peaks, the Super Sucker added 14.9 horsepower and 10.4 foot-pounds of torque (again at peak).

There go the assumptions. In theory, the two-inch model should have made even more power. So how in the world does this thing work?

I asked that of Keith Petelle of High Velocity Heads. He said, "These spacers work, obviously, by helping the fuel distribution. If you look at the bottom of the spacer, you'll see that the shape is different [in comparison to other spacers]. We wanted to improve the feeding of the outside runners on a single four-barrel manifold. The design picks up the air speed and gives it a specific direction. Finally, the plastic composite material insulates the carburetor.

Plenty of people are skeptical. Many people will think that if they spend big money on a hand-fabricated intake manifold, they don't need a spacer. We've had some racers with very powerful engines see major gains. We've had some used on Comp engines. The spacers don't discriminate between expensive, high-horsepower engines and low-cost, low-horsepower engines. They work equally well on either small-displacement engines or big ones. We typically see power increases in the range you found. We've seen more, but it really does depend on the engine and the type of manifold used."

Currently, HVH spacers are made from solid plastic composite stock on Haas CNC mill equipment. The company offers one-inch- and two-inch-tall four-hole spacers for 4150 Holley carburetors, one-inch- and two-inch-tall four-hole spacers for Holley Dominator carburetors, open one-inch-tall spacers for Holley 4412 carburetors, and one-inch-tall two-hole spacers for Holley 4412 carburetors.

The spacers aren't cheap at a price range between $85 and $105 (racer's net), but they do provide cheap power, and in a well-sorted engine, 15 horsepower for 85 bucks can be considered a bargain.

My preconceived notions were definitely wrong: There is power to be gained from a carb spacer, but it takes a special configuration like the one used on the Super Sucker to make it happen.

James L. Martin


 Reprinted with permission from National Dragster http://www.nhra.com/