This is the second installment in my 540 adventures over the past few years. I will show the results of a carb change on the combo after replacing the intake in Part 1.

As I mentioned in Part 1, I originally had a Demon 850 Vac Secondary Carb. I do not have any electronic copies of the Dyno pulls and I have no confidence in those results anyway (that dyno seems a little happy compared to the one that I used for all of the results that I am posting here). The Demon had decent driveability, but after talking to Jim (427HotRod), I got the impression that I might be leaving some power on the table. Jim was suprised that I couldn't brake the tires loose shifting into third gear. He had a spare 850 double pumper and suggested that I give that a try. I was very skeptical at first, having read all of the magazines and been subjected to the conventional wisdom that only vacuum secondaries can work on the street. Jim finally talked me into giving the Double Pumper carb a try. He even brought the carb to me in person all of the way from Houston, so how could I say no. I am very glad that I finally listened. Jim described the grin on my face as ear to ear when we took the car out for a quick run. I smoked the tires in first and second and third gear for the first time. I also noticed an immediate improvement in driveability. I later found that fuel mileage had improved by 2mpg around town and 4mpg on the highway. Needless to say I was very pleased with these results. This is the carb that I used in Part 1 of the Saga. As much as I liked the carb, Jim couldn't sell it to me and I figured that I was probably still leaving some power on the table by not having a larger carb. I saw about 3 inches of manifold vacuum at wide open throttle, so the 850 was proving to be a restriction for the rest of the combo. I decided to give the new Holley HP 1000cfm a try and here are the performance results:

Holley HP 1000 Carb
540 C.I., 9.1:1 C.R.
H.R. 232/244 .585/.595 110
Holley HP1000 DP Carb
Holley Strip Dominator Ported

RPM HP FT-LBS.
2200 184 440
2300 196 447
2400 204 446
2500 213 447
2600 224 452
2700 236 460
2800 251 472
2900 269 487
3000 282 494
3100 296 501
3200 307 505
3300 319 507
3400 329 508
3500 338 507
3600 347 506
3700 355 504
3800 363 501
3900 370 498
4000 377 496
4100 380 487
4200 384 481
4300 385 470
4400 396 472
4500 402 469
4600 410 468
4700 417 466
4800 422 462
4900 430 461
5000 430 452
5100 437 450
5200 437 441
5300 437 433
5400 434 422
5500 428 408
5600 417 391
5700 404 373
5800 382 346
5900 361 322
6000 355 311
6100
+12 +9
MAX 437 508


This is an increase of 36 HP and 4 FT/LBS. over the Baseline combination with the 850 DP and Dual Plane LS-6 Intake. This was an increase of 12 HP and 9 FT/LBS. over the previous combo of the 850 DP and the Holley Strip Dominator Single Plane intake manifold.

I did not experience any reduction in driveability and I managed to pull down 18 mpg on my first trip to the Corvette Forum Cruise In at Bowling Green.

Up to this point, everything I have done to feed more air to the engine has increased power, driveability and fuel mileage contrary to what conventional wisdom says should happen. I think that the conventional wisdom is quite correct for a 396 or 427, but definitely breaks down when discussing 540's and up.

I owe a big thank you to 427HotRod (Jim) for hauling the carb up here and challenging my thinking on what works and doesn't work on the street.

 

Too bad you have already bought that expensive Holley 1100. For a few dollars more I would have suggested you get into the BG carbs with replaceable sleeves. Now you would really have some playing around room. They seem to have the uper end market covered expertly. Might want to look into them and possibly sell your Holley. Keep diggin' Good runnin

 

THIS ought to be fun. Let's get Nick and quite a few others started on BG..their products and their customer service or lack thereof!!

I think they have some neat products, but I surely don't see them as the masters of the Holley designed carb. Those replaceable sleeves are sorta neat if you are using the same carb on several motors, but if you select right stuff up front it's really not that great, plus thsoe sleeves aren't cheap either.

That HP carb worked perfect out of the box, made great power AND got 18.9 mpg on a 540" motor!!

You should see the new carb he has for the newest combo! I'll let him talk about that later.


JIM

 

Ya, take a stroll through any pits and you see Holleys on 95% of the race cars.

 

BG's got good marketing folks!



JIM