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.

 

Good to hear you picked up some more hp,
Im headed that route myself ,on my 427 sb with dart pro 1 alum 230 ,comp solid roller 620 lift and a 750 dblp holley.
The motor feels really strong but i feel there can be some improvement switching to a bigger carb,thinking of getting a 950 holley,maybe the 1000cfm is too big for me.
Keep up the good work!

 

Gonna be some red-faced folks reading this...

Brett

 

Brettmc,
Why are there going to be some redfaced people reading this? I am just sharing what I have experienced so far.

 

really wake that motor up with a dominator.

 

Well, you've prolly read the threads with this: "you don't need a carb that big" or "I wouldn't put an 850 dp on that engine, it's too big" or "you will lose all throttle response with that big of a carb" or "double pumpers are for the dragstrip only". Not directly quoting threads but that's the idea.

It's been proven time and again a bigger carb isn't bad...in fact it's a good thing. Maybe your series prove this once and for all.

Regarding your cam, I've got one similarly sized (albeit a solid ft) and it's quite mild in my 468. I would think a 540 would like a much bigger stick...but that's prolly for a future part of this story....

Brett

 

Folks complain about carbs anyway, but it seems they complain about demon carbs the most.

 

I agree on this. A 540 could use a lot more cam than this. That is a tame cam in a 454 motor. Run more cam and a big carb and the HP numbers will be a lot better.

 

Nick had a fantastic motor for what he originally planned for this thing. He literally did drive it in Dallas traffic everyday to work. He wanted dead nuts reliability and driveability..and the ability to spank whatever else was lilely to come up beside him in daily commuter traffic, so it did well there in all respects. In fact he just did leak down tests the other day and it still is in the 3% range with regular rings and maybe 25K miles on it. Good solid motor.

He followed all the prescribed TQ methodology during it's design, which placed components on the mild side. The issue was that all those things stacked up and I often accused him of having an ungodly motorhome or tow truck motor! It was an animal in the lower and midrange areas, but ran out of breath early.

All these things he tried were all aimed at letting it breathe a little. Trust me we had LOTS of cam discussions..and you folks KNOW how much I like Hyd roller stuff......yeeccchhhh!!

I'll chime in more as we get further into some more tests, but you can see where this is headed. Better breathing has added up to more power, better driveabilty, better mileage etc even when dealing with something this big. Remember..this beast gets 18+ mpg and has A/C on it!! With 540 " and a 1000 cfm carburetor!! You should see it make a 1/4 mile run on plain street radials..sideways at halftrack and still running a killer ET!! But I digress...that's another chapter!

Jump in and ask for more details as needed.....he's just whetting your appetite right now. Folks could save a lot of $$ and aggravation by studying some of this stuff.nd trust me

A trust me..we had the Dominator discussions too...had a little hood clearance issue....but we won't for long!

And again that's 36 RWHP at peak and more in parts of curve as well as hanging on much better as rpm rises. Think what that is at the crank with just a carb and intake change. Big time buttometer improvements!


JIM

 

Let's seeeeee.....437 hp and 508 tq at the wheels. Figuring in 15% drivetrain loss...that's 503 and 584 at the crank....20% loss would be 524 and 609. Quite respectable in anyone's book.

I wonder what the difference was in AVG hp and tq over the entire range?

Brett

 

Brettmc,
The average horsepower and torque across the measured rpm range were the following:

Baseline 333 434
Holley Strip Dominator Intake 342 448
HP1000 Carb 348 455

That would put the Avg. HP +9 and Tq. +14 from the Baseline for the Intake change. The Carb and Intake combo are HP +15 and Tq. +21.

 

What matters is how well the final setup meets the design requirements & if the owner is happy w/ it. Sounds on target.

Nick
Looking good.
No reving up needed to launch- what I call a Go Fast Quietly setup.



1000 CFM is excellent for the setup.

 

This last Friday I was at a race shop that for the last few years has been entering the national motor building contests. But anyway last year they came in sixth place.

They had a customers 572 merlin aluminum on the dyno stand and it was built for pump gas to go in someones 69 Camero. It was a H-Roller and no pulls exceeded 5800 rpm. It was equiped with a 850 Demon carb. I ask if they thought that it kind of small for a 572 CI? :o They said that since it was for street driving and pump gas the loss of small hp was not a big deal.

Running 4 inch race mufflers it topped 708 hp on 92 octane

 

Nice! Those are changes you can feel. At this point of the progression, I'll bet you were liking the new power but thinking "how much MORE power would it make if..."

Brett

 

Gkull,
I would love to see more details on that 572 if you can get them. I would like to know the usual info like cam specs, compression ration, head work done, intake used, etc.

Do you know if the Demon was a VS or MS?

Given the results that I have seen with all of my testing, I am certain that a Holley 1000HP would not have hurt driveability the least little bit on that engine, and they would have seen an increase in power.

708 Engine HP, assuming a 15% loss would be 602 RWHP. That is very impressive.

 

The 572 ci uses a mech secondary 850 Demon. I could find out specifics on the motor. But just in our talk while it was warming up, it has about 10 more degrees intake and exhaust then you do. But where it gets the power is from the 10.8 compression with Brodix BB2-X heads. They might have been the BB2-xetra. So they really flow and they are either 340 or 360 cc intakes. Also matching Brodix single plane intake. I think that the headers were 2 1/4

I just met them through friends the Shop is called "Kidd Performance" out of Twin Falls Idaho. The Owner is Mark Kidd who is a very acomplished dragster racer.

 

 

Gkull,
I can see the Brodix BB2-Xtra's making that kind of power with the right cam and those headers. My car had the Hooker Super Comp 1-7/8 headers for all of these tests. The compression is also a big plus as Part 3 will show.

 

I'm running hogged out to somewhat port match with a head lower lip antireversion idea 1 3/4 headers on my 427 small block and I'm thinking that I need to get bigger headers.

I've always tried for as much compression as i could get away with using pump gas.