Chevy Small Block Part 17 - PT. 17: Fresh Off The Old Block

DM Is Rebuilt and Ready for a New Year

Mike Petralia Feb 1, 2004 0 Comment(s)
Sucp_0402_16_z Chevy_small_block_part_17 Ring_spacer 1/12

After we found some extra power by installing this simple plastic ring, we began to wonder if maybe a carburetor would benefit from the same. But Holley includes this ring only as an adapter; it's not supposed to make extra power. Carburetor experts and racing engine builders George and Bob Vrbancic both think the extra TBI power came from the fact that a throttle body normally chokes airflow into itself because of the large injectors that hang directly above the venturi bores. Unfortunately, you cannot move the injectors any higher to increase airflow because that'll cause the fuel to spray outside of the venturi. So, instead you can try to improve airflow into the venturi by smoothing its entrance. Apparently, this plastic ring accomplishes that. And installing a tall velocity stack, which has been the normal way to improve airflow into carburetors for years, added just a little more power still, further proving our theory.

Test 27 Test 28 Test 29 Test 30
CARB TBI CARB TBI
RPM TQ HP TQ HP TQ HP TQ HP
2600 359 178 373 185 362 179 371 183
2800 383 204 387 206 385 205 383 204
3000 398 227 397 226 401 229 389 222
3200 402 245 396 241 410 250 395 240
3400 398 257 394 254 411 266 398 257
3600 393 269 391 268 412 282 397 272
3800 394 285 386 279 410 297 403 292
4000 407 307 389 296 415 316 405 308
4200 417 334 404 323 415 332 401 321
4400 421 353 409 343 412 345 391 328
4600 417 365 409 359 407 356 391 342
4800 413 378 402 368 402 368 392 358
5000 408 389 394 375 398 379 392 373
5200 402 398 381 377 389 385 387 383



5400 396 407 367 378 380 391 380 391
5600 390 415 365 389 374 399 375 394
5800 379 418 354 391 358 395 350 385
Max 421 419 409 391 415 399 405 394
Avg 397 325 388 309 397 316 388 309



Sucp_0402_14_z Chevy_small_block_part_17 Mounting_system 2/12

Here you can see a close up of our trick mounting system developed to secure the air cleaner adapter ring and K&N velocity stack. No good dyno shop would be complete without a roll of duct tape! Also, check out the fuel pressure regulator built into the back of the Holley throttle body centered between the two hoses. The inlet hose (right) gets high-pressure fuel from the electric pump and return hose (left) sends unused fuel back to the tank.

We're always looking for new ideas. Do you have a better one for Danger Mouse? Send your test suggestions to:
Super Chevy Magazine
Attn: Danger Mouse
720 Hundley Way
Placentia, CA 92870
Or e-mail: terry.cole@primedia.com

Sources

Comp Cams
Memphis, TN 38118
800-999-0853
http://www.compcams.com
Speed-O-Motive
West Covina, CA 91790
626-869-0270
www.speedomotive.com
Holley Performance Products
Bowling Green, KY 42101
270-781-9741
http://www.holley.com
Vrbancic Brothers Racing
909-930-9980
www.customcarbs.com
Lunati LLC
Olive Branch, MS
662-892-1500
LunatiPower.com
Speed-Pro
Muskegon, MI 49443,

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