I know this topic always comes up, but here's my question. I'm going to buy a 470 hp 383 from AR Racing this summer and need to pick out a carb. The motor was dyno tested with the Holley 750 double pumper, but I'm not a big fan of those carbs. I currently have a Holley Street Avenger 670cfm on my 350. But it won't be enough for this 383. So I'm looking at the Speed Demon 750 mechanical secondary carb with no choke, the Speed Demon 750 vacuum secondary with electric choke, and the Holley Street Avenger 770 with vaccum secondaries and electric choke. The car will be daily driven during the warmer months, and not driven at all during the winter. As you can tell I'm going in the direction of performance with this car, and for that reason would favor the mechanical secondary Speed Demon 750, but it has no choke. The car will be daily driven in the summer though, so for that reason I would favor one of the vacuum secondary carbs with the electric choke. I'm very happy with the performance of my current Street Avenger, so that's why it's included in my search for a carb. Which way should I go :confused:. Or someone could make it real simple for me and tell me which carb will be give me the most horsepower/torque :D





[Modified by Ryan77, 3:30 PM 1/29/2003]

 

Speed Demon, Vac Secondary, Elec choke.

 

:withstupid:

 

:iagree:

Barry Grant makes some good stuff.

 

So far the Speed Demon 750, electric choke, vacuum secondary is ahead 3 votes to 0 :eek:

 

TTT :thumbs:

 

CARBS Tests TQ/HP http://www.corvettefaq.com/c3/carbcomparo.htm

 

Ganey,

TQ.......................HP.........
347 @ 4200 ... 361 @ 6100 ... Holley 4777 650 Carb Shop
338 @ 4400 ... 363 @ 6100 ... Speed Demon 650
336 @ 4000 ... 360 @ 6100 ... Holley 750 3310 JET Perf.

If I read this correctly, a properly set up 4777 650 DP is better than a 750 3310 vac secondary.

What was modified by the Carb Shop. to get the 650 to perform with those numbers? I have the 650 in question and had been toying with the 750 since I have a source for one.

 

Check out the latest issue of Super Chevy (I got mine yesterday in the mail). There's a Holley carb shootout in which they try 12 different ones on Danger Mouse. The HP series won. You might want to check into one of those. Too bad I just ordered an 850 doublepumper for my 468 day before yesterday. :banghead:

Brett :thumbs:

 

Robert

The engine only made about 360 HP & 650 was all it needed. A higher HP setup could use the 750.
Remember a carb is a responsive device.

Brettmc
Yes, that is a very good choice- almost said Holley HP yesterday.

Don't normally get involved w/ best carb topics.

Prefer blondes & Holleys.

:cool:

 

Ganey,

Thanks. There have been so many post regarding what is better - vac secondary, DP and cfm sizes. Sounds like the 750 on my engine should be about right.

 

Well, I re-read the carb section in my Summit Catalog and found that that there IS a choke kit available for the mechanical secondary carb, it has to be ordered seperate, you can't get them with the choke already installed. It doesn't specify whether this is a manual or electric choke either. Does this change anyone's opinions, or is the Speed Demon 750, vac secondary, electric choke still the winner? :cheers:

 

Anyone :confused:

 

Well, I'm set a Speed Demon 750. But I'm still debating on vacuum or mechanical secondaries. From what I've heard the mechanical secondaries make more power and have better throttle response, and the vacuum secondaries are smoother, but don't respond as quick and make a little less power. So should I get the vacuum or mechanical, or can someone give me the pros and cons of both so I can decide myself which I would prefer? I can get either one with a choke. Thanks in advance :cheers:

Ganey- which carb are you running on your car?


[Modified by Ryan77, 7:53 PM 2/5/2003]

 

Well it's settled :yesnod:. I'll be buying the mechanical secondaries Speed Demon 750 with no choke. I IM'd Lars and here's what he said:

"Ryan - We (the CCC - the Colorado Corvette Crazies - the Ultimate Vette Tuning and Beer Drinking Fraternity) have installed and tested quite a few Holleys and BGs (actual dyno runs). You're right in choosing a BG - the Speed Demon will outperform anything else on the market by 15-20 hp. I also agree with your 750cfm choice - we've had exceptional luck with these on radical 350s and moderate 383s. We have also noticed that the vac sec carbs are very slow transitioning into the secondaries, and they will not achieve full secondary opening with the stock springs. As a result, we are now opting for the mechanical sec carbs without choke. These run incredibly well, as long as you don't mind "feathering" the gas pedal for the first 90 seconds of engine operation. We have been able to get the vac sec carbs to run well by installing the softest available spring in the sec diaphragm. However, after comparing the vac sec to the mech sec carbs, we feel this is a compromise. For peak power, use the mech sec carb without choke. If your girlfriend/wife (hopefully not both...) is driving the car, use the vac sec with choke. But then we'll have to make fun of you and call you names at out next gathering.... Good luck - tag me back if you need further info or assistance."
-Lars

I'll take his carb advice anyday:yesnod: :cheers:


[Modified by Ryan77, 5:30 PM 2/6/2003]

 

Good Luck you want regret getting the Demon