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Small Block Chevy Holley Carb Tests - Danger Mouse Part 8

Carbureting For Power

By Mike Petralia

CLICK BELOW TO SEE ALL OF THE STORIES COVERING THE BUILD OF PROJECT DANGER MOUSE

DANGER MOUSE PART 1

DANGER MOUSE PART 3

DANGER MOUSE PART 4

DANGER MOUSE PART 5

DANGER MOUSE PART 7

DANGER MOUSE PART 8

DANGER MOUSE PART 9

DANGER MOUSE PART 10

DANGER MOUSE PART 13

DANGER MOUSE PART 14

DANGER MOUSE PART 15

DANGER MOUSE PART 18

DANGER MOUSE PART 20

DANGER MOUSE PART 22

DANGER MOUSE PART 23

DANGER MOUSE PART 24

DANGER MOUSE PART 25

We Tested 12 Different Holley Carbs For Power
This month, we took Danger Mouse (DM) in a completely different direction. In the past seven months, we've used DM to tackle various ideas on the dyno and see just how much power we really could make with a genuine street small-block. For the most part, the results have been fantastic, and DM has usually surpassed all power expectations. For our eighth installment on DM's testing schedule, we wanted to see if there really was power to be gained or lost by running the right or wrong carburetor.

Now, this type of testing can open up a whole, big can of worms, so to keep testing simple and fair, we chose to only run carbs from the same manufacturer, Holley. And we also chose to test only 4160- and 4150-style carbs, and not the giant 4500-series Dominator lineup. We gathered up 12 different size/style carbs, ranging from Holley's smallest four-barrel, the 390-cfm vacuum secondary unit, up to the big HP950 double pumper, and bolted each one of them onto DM to see if one stood out from the rest.

We expected the smaller carbs to make good bottom-end torque but sacrifice peak power, which they did. But the thing that really threw us for a loop was that the biggest carb we tested-the HP950-made the most power of any carb! Does this mean that big carbs are best? Probably not, but it does mean that Danger Mouse liked the bigger carb. However, DM also liked the HP 750, and we think these tests really show that Holley's engineers have done their homework and dialed in the HP carbs to work best on just about any engine. It also means that all of those carburetor modifiers out there probably do have something good going, because most of them can take an old, abused Holley and make it work as good as a new HP, but the cost is about the same as if you just bought a new one, so which choice you make is up to you. From what we learned in this test vs. what we'd already known is that not all carbs are created equal, and if you're building a daily-driven street car, you should still go with something smaller than 800 cfm. But, you certainly can't judge a carb by its size alone. Check out the dyno charts to see what we found.

This month was the first time we bolted DM onto the Vrbancic Brothers Racing DTS dyno in Ontario, California. Shop owners George and Bob Vrbancic both supervised the test sessions with George at the dyno controls. Yours truly performed all the jet changes and kept a running tab of the results.

To establish a baseline we first ran Holley's old standard, the 750-cfm double-pumper (List 0-4779-8). After the baseline was done, we tested from smallest to largest, trying every different size Holley carb we could get our hands on. And in order to ensure accurate results we tried tuning fuel curves for the best peak power. It turned out, however, that the stock fuel curves worked best, and any time we strayed from Holley's settings for each carb, we usually sacrificed some power.

The Holley carb flow ratings (cfm= cubic feet per minute) and List numbers (also known as part numbers) are shown for each carb tested.

dp = Double-pumper carb
vs = Vacuum secondary carb
Baseline
750-cfm dp 390-cfm vs 570-cfm vs 600-cfm vs 650-cfm dp
(0-4779-8) (0-8007) (0-80570) (0-1850-6) (0-4777-7)
RPM TQ HP TQ HP TQ HP TQ HP TQ HP
2500 323 154 346 165 347 165 339 161 352 167
3000 401 229 403 230 400 229 388 222 399 228
3500 417* 278* 405 270 404 269 410 273 417* 278*
4000 425 324 413 314 413 314 420 320 418 318
4500 423 362 403 345 407 349 411 352 416 356
5000 409 389 385 367 393 374 401 381 406 387
5500 386 405 358 375 367 384 374 392 380 398
6000 341 389 318 364 325 371 330 377 340 388
Peak 429 406 414 376 415 385 421 393 421 398
@ 4200 5600 4100 5600 4100 5600 4100 5600 4200 5400
Avg 399 323 386 309 389 312 391 315 397 320
670-cfm vs 750-cfm vs HP750 dp 800-cfm dp 830-cfm dp
(0-80670) (0-3310-5) (0-80528-1) (0-4780-6) (0-9381)
RPM TQ HP TQ HP TQ HP TQ HP TQ HP
2500 344 164 337 160 356 169 343 163 340 162
3000 391 223 386 221 401 229 404 230 402 230
3500 403 269 388 259 416 276 410 274 416 277
4000 417 317 394 300 429* 327* 424* 323 422 321
4500 411 352 396 340 422 362 418 358 420 360
5000 401 381 388 370 414 394 406 387 407 387
5500 373 391 371 389 388 407 379 397 380 398
6000 332 379 331 379 343 392 336 384 341 389
Peak 419 391 400 391 431 408 427 399 427 403
@ 4100 5600 4300 5700 4100 5600 4200 5700 4200 5700
Avg 390 315 380 307 403 325 398 321 398 321
850 dp HP950 dp
(0-4781-8) (0-80496-1)
RPM TQ HP TQ HP
2500 347 165 353* 168*
3000 406 232 407* 232*
3500 412 274 414 276
4000 427 325 429* 327*
4500 421 361 424* 364*
5000 409 390 415* 395*
5500 384 402 390* 409*
6000 341 389 347* 396*
Peak 429 403 432* 409*
@ 4100 5700 4200 5500
Avg 401 323 404* 326*

* = Indicates highest figure recorded
*t = Indicates a tie for highest figure

Some Interesting Dyno Observations
*Only three (850 dp, HP750, and HP950) of the carbs averaged over 400 lb-ft of torque, and only the two HP carbs (750 & 950) peaked over 430 lb-ft of torque.
*The HP950 made more torque at 2,500 rpm (353 lb-ft) than any other carb, but the 650 dp was right behind it with only 1-less lb-ft (352).
*The 650 and 750 dps tied for most tq and hp at 3,500 rpm.
*The 750 vacuum secondary carb (List 0-3310) had the lowest mid-range figures of all carbs.
*Peak torque occurred between 4,100 and 4,300 rpm, and peak hp occurred between 5,400 and 5,700 rpm with every carb.
*Average power tells the story and the two HP carbs (750 and 950) made more average power than any other carb.
*Note: Faithful DM followers may note that peak power numbers for this test were down by a couple percent from previous tests. That discrepancy is most likely just the difference between how a DTS dyno and a Superflow dyno collect and interprets the data. It's kind of like stepping on the scale at your house vs. your friend's house; either scale may be correct, but you'd still weigh the same regardless of the difference in readings.

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By Mike Petralia
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