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My First Intake and Carb Upgrade (continued)
With the car at Willis Automotive, we were ready to make our dyno runs. Keep in mind, on this day we didn't dyno the car in true "stock" form, with the original factory intake and two-barrel carburetor. We know from past experience the factory 2V 289's put out an anemic 150-155 horsepower to the wheels and are lucky to crack 200 ft-lbs. We were more interested in comparing between the two combos identified on the previous page.

Round 1 - Edelbrock Performer Combo
The first run of the day would be with the Edelbrock Performer intake and matching EPS 600cfm carburetor. Other than setting the idle speed, no prior tuning was performed. After making a couple of pulls to adjust the timing and get consistent results we found the motor liked 40 degrees total advance, in by 3500 rpm. Our best Edelbrock dyno run yielded a peak 176 horsepower and 224 ft-lbs of torque (refer to red plots on dyno graph below). The air-fuel ratio was impressively rock-steady at an ideal 13:1. Little did we know at the time, these would be our numbers to beat.

Round 2 -Weiand - Holley Combos
As the engine cooled we pulled the Edelbrock combo and bolted on our Weiand/Holley combo. As mentioned above, we had our choice of either the 570 of 670 cfm Street Avenger. There are some at Holley who calculate 570cfm as the right choice for a stock 289, while others (including Jim Dralle) are adamant the 670cfm is more appropriate. We tested both, first the 570.

Like the Edelbrock EPS, the 570cfm Street Avenger is a vacuum secondary and electric choke carburetor. This combo also fired right up without fuss.

We got our Holley 570cfm Street-Avenger carburetor and Weiand Action-Plus manifold assembled beforehand to cut-down on swap time at the dyno.
We made the swap in under an hour as the motor cooled after our Edelbrock dyno runs. Notice we left the distributor in place to avoid having to reset the timing.

We adjusted the idle speed and made an initial pull with this combination. The results were 172 horsepower and 218 ft-lbs of torque. We noticed the air-fuel ratios were dipping into the low 11's. In attempts to lean it out we changed the vacuum secondary spring to the lightest one included with the carburetor. Since the carb comes with pretty small primary jets (54's) we left them alone. On the second pull, air-fuel ratios were improved to high 12's, but still not near the 13:1 we'd like to see for this engine. While peak power matched the Edelbrock combo at 179 horsepower (4600rpm), focusing on the peak would be very misleading. Power was down across the board in the lower rpms, by as much as 12 horsepower. Torque was also down about 6 to 10 ft-lbs across the board, for a peak of 221 ft-lbs at 4000rpm.

Well aware that the 570cfm Street Avenger may be undersized, we performed another test with a 670cfm carburetor - also a vacuum secondary Street Avenger.

We also tested a 670cfm Holley Street Avenger. Our stock 289, however, didn't respond to the increased air flow capability.
The upside to Holley carburetors is the infinite tuneability. However, for the novice this can be the downside too. A jet kit, vacuum spring set, and pump/needle tuning kit are wise investments with any Holley carbuertor purchase.

We changed the vacuum secondary spring to the lightest one possible in order to ensure the secondaries would open fast and completely. This didn't do much for our overall power output however.
The 670cfm comes with 65 jets in the primary and secondary metering blocks.

Again, we had to perform some tuning to get the air-fuel ratios out of the rich range. First up was the lightest vacuum secondary spring. We followed this by changing the primary jetting from 65's as delivered, to 60's. On our final pull we were still seeing air-fuel ratios in the low 12's at wide-open, but this was a marked improvement on the high 10's we saw out of the box.

The 670cfm proved to be a much better match for our 289. We'd clearly recommend no less than a 650cfm carb for any stock 289/302. The 670cfm made the most peak horsepower at [email protected] In fact, the 670 seemed to be coming alive in this rpm range, but our stock cam and valve springs weren't going any further. However, as with the 570cfm carb, the excess fuel killed the average numbers. We made an effort at tuning the 670 for about four pulls, but simply ran out of dyno time.

Who Wins?
Before we get into the conclusions, it is important to remember that the combinations would perform differently on an engine with more modifications - particularly where there is a greater demand for air-flow via a larger camshaft, ported heads, or more cubic inches.

With that said, when it comes to a bolt-on, no fuss carburetor, we have to hand it to Edelbrock. The have nailed it with the #1406 Performer series carburetor. On a stock engine like our 289, the 600cfm Edelbrock performed flawlessly. Other then setting the idle speed, we didn't need to perform any other tuning. The air-fuel ratios were dead-on at 13.1 throughout the rpm range. The Edelbrock combo yields very consistent results, great torque and horsepower across the board.

On the Holley side, we must say we weren't surprised. The 570 and 670cfm Holley Street Avengers are great carburetors, but they need to be tuned. Holley tends to jet them in anticipation of a modified motor, and this means they are on the rich side. On a simple motor like this one, you get penalized with losses in power until you tune the carburetor properly. The question is, whether that is a reasonable demand to place on a new enthusiast looking to take their first step into engine mods. We think it may be asking too much - even the average enthusiast will not spend the money and time to tune on the dyno like we did. We know Holley's will make more peak power, you can see them pulling away at the end of the curves, but we'd like to see Holley really develop a carb that performs across the power curve, straight out of the box.

With the manifold selection, we are happy to say that there are now two equally good candidates out there for small block Fords running up to 5500 rpm. In fact, we decided to throw together a little "wildcard" combo, where we tested the Edelbrock carburetor atop the Action Plus manifold. Our seat of the pants impression of this hybrid combo was "holy smokes, this is the strongest this car has ever felt". The dyno results confirmed this, showing slight gains everywhere with the Action Plus over the Performer manifold.

Round 3 - Wildcard Combo! Edelbrock Carburetor & Weiand Manifold

The Action Plus' runner flow balance claims may prove to give the manifold a slight edge. To isolate the effects of each manifold we dynoed the Edelbrock 1406 carburetor atop the Action Plus manifold. This combo made a peak of 171 horsepower compared to 166 for the Edelbrock/Edelbrock combo, and average power was up a handful across the rpm range with the Action Plus intake. Torque was also up by 6 ft-lbs at peak. We'll have to schedule a round two in the near future to see how the Action Plus would do on a little more aggressive engine.

The Bottom Line

Want a no-fuss, minimal tuning, idle to 5500rpm combo that makes excellent power? This is it.

Perhaps for some this article will make the decision easy, but we suspect for most it will only fan the flames of the Edelbrock versus Holley debate. Our advice is to ask yourself if you want a no-fuss, bolt on and go combination that will run flawless for years to come. If so, the red lines in the charts above are all you need. Or do you anticipate making more modifications to your engine, and thereby prefer a combination that can grow with you. Do you like tuning, and searching for maximum power from every combination? If so, get a Holley and a tuning kit and never look back. Or, if you don't want to think about it that much, split the difference and go for the Wildcard combo.

We're planning more intake and carb tests, so tell us below what combinations you'd like to see tested.

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Holley Performance Products

1801 Russellville Rd.
P.O. Box 10360
Bowling Green, KY 42102-7360
270 781-9741

2700 California Street
Torrance, CA 90503

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