Which carb? Im confused.

NosPony

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Nov 8, 2004

#1

• Nov 8, 2004

• #1

Well the problem is easy. I can't decide between a 750 Holley DP or a 750 Speed Demon. Which would you choose? What are the pros and cons of each in your guys opinion. Oh please help me decide.

 

NosPony

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Canton, Il

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#2

• Nov 8, 2004

• #2

anyone???

 

T

tjm73

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Aug 3, 2000

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Rush, NY

Nov 8, 2004

#3

• Nov 8, 2004

• #3

What's your engine combo? I'd go speed demon myself.

 

N8Miller

I need NOS....make it 2 of the big ones

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Kingston, PA, USA

Nov 8, 2004

#4

• Nov 8, 2004

• #4

etiher way your not gonna go wrong. the speed demons are pricey, but worth the money from what i hear. It all depends on your setup and what your looking for/going to spend.

 

Fishhawk

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#5

• Nov 8, 2004

• #5

NosPony said:

Well the problem is easy. I can't decide between a 750 Holley DP or a 750 Speed Demon. Which would you choose? What are the pros and cons of each in your guys opinion. Oh please help me decide.

Click to expand...

Personally I think the 750 is to much carb for the 5.0. I tried a 750 vaccum secondary on my 85 and lost 4/10's in the quarter. I finally settled on a 650 and feel I have found the right carb. I also talked to a few drvers at two NMRA events this past summer and one thing most of them had in common was if they were running 302 ci's, they didn't go with anything larger then 650 cfm's. Even a couple guys with 347 strokers agreed 650 cfm was the way to go.

 

B

Boss 351

Here sthhhhhhhheeeve take a picthh of my man flowe

Jul 13, 2003

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Nov 8, 2004

#6

• Nov 8, 2004

• #6

750 would be good with a 408 stroker though lol I got a 650 mechanical double pumper and the engine just loves that shnit!

 

NosPony

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Nov 9, 2004

#7

• Nov 9, 2004

• #7

The reason I am going to use a 750 cfm carb is DSS Racing told me to use that size with my motor. It a pro bullet 306 with world windsor jr heads on it.

 

crazypete

All my crevices are greased.

Oct 22, 2004

930

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Arlington, MA

Nov 9, 2004

#8

• Nov 9, 2004

• #8

With carbs, less is more. I had a 670 vacuum holley street avenger and the performance was ok. I move down to a 600 dp and oh my goodness. It idles, revs and everything else so much cleaner and crisper. A carb lives off vacuum signal so if you go overboard and you lose that, the car will not be too much fun to drive and wont be very responsive. Hey, the Nascar stockcars run like 390 CFM carbs.

I vote holley by the way! They are infinitely tuneable and after my extremely pleasant experiences with holley performance (they replaced 2 carbs for me for free and gave me a free upgrade from 570-670), I vote holley all the way.

 

Dark Knight

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Nov 9, 2004

#9

• Nov 9, 2004

• #9

demons are nice, but it's harder to find gaskets etc.. most parts stores carry holley stuff..

might want to step up to a performer rpm though..

 

NosPony

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Nov 9, 2004

#10

• Nov 9, 2004

• #10

I have a victor jr I am going to run on the motor.

 

NosPony

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Nov 9, 2004

#11

• Nov 9, 2004

• #11

Any pros and cons of either carb?

 

S

SmockDoiley

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Jun 14, 2003

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San Diego, CA

Nov 9, 2004

#12

• Nov 9, 2004

• #12

Well do whatever you want, but a even a 306 pushing 7500 rpms only requires a 735 cfm carburetor with 85% VE. What is the max rpm you plan on pushing? Also, if you are using Windsor Jrs, they have runners too small to be compatible with a large carb and intake. I believe they are a 180 cfm intake where as a 200 would be needed to support the rpms required to really take advantage of a 750 and vic intake.

 

NosPony

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Nov 10, 2004

#13

• Nov 10, 2004

• #13

Hmm wonder why DSS told me to run that big of carb with my motor then SmockDoiley.

 

NosPony

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Nov 10, 2004

#14

• Nov 10, 2004

• #14

Seems like holley is the way to go for tuneablility, right? Demons are good or bad carbs

 

8

83GT289

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#15

• Nov 10, 2004

• #15

demons are basically polished off holleys. Same basic design but prettied up a bit for better airflow. Demons are in no way bad carbs. People who run demons will swear by them. People who run holleys will swear by them. It comes down to a matter of personal preference. For your setup i think a 650 speed demon with mechanical secondaries would be an awesome choice. That's what i'm putting on mine when i have the cash to spend on it. If you get a holley street avenger it will be easier to tune than a holley DP. Easier to tune does not = better. Generally the opposite applies. The demons and holley DP's have 4 corner idle adjustment. They will be a little bit harder to get tuned at the start, but because of this they end up more tuned to your exact needs when you are done.

My vote goes to the 650 speed demon mechanical secondary.


J.

 

crazypete

All my crevices are greased.

Oct 22, 2004

930

4

18

Arlington, MA

Nov 10, 2004

#16

• Nov 10, 2004

• #16

Go with the 650 DP holley mechanical secondary race carb. The 4 corner idle is amazing.

Lets put it this way: last night was the coldest night this year up here in new england. I was able to cold start the car after 2-3 seconds of cranking with no choke at all. It ran and idled just fine. Wow

I'd stray away from the avengers. Theyre too new. I owned 2 so far and both had badly drilled vacuum advance ports.

 

NosPony

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Nov 10, 2004

#17

• Nov 10, 2004

• #17

The info u guys are giving is helping a ton anymore comments.

 

S

SmockDoiley

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#18

• Nov 10, 2004

• #18

Either carb will work fine. But the flow is better in a Demon and they use better parts. The Demons are also a great looking carb which has always been a killer with me on the Holleys. Holleys are a great carb, and they are cheaper. They also have a larger base of parts, but lots of parts from Holley and Demon interchange. I'm saying either a Holley or Demon 650 Double Pumper.
As for what DSS says. First off, they are engine builders not racers so they arent the best people to talk to about that choice. They are also a race engine oriented company so when they see someone ordering a Super Pro Bullet they are expecting your going to race the crap out of it. So what they advice may not translate to well if your more of a street guy. Not that a 750 wouldnt run but your engine may not have the pull power to correctly generate the right amount of vacuum to operate the carb right. You can easily generate a "lazy engine" by over carbing. If your building a street car with a mild displacement, and mediocre compression then a 750 is a step in the wrong direction. For your 5.0 the real power band of a 750 probably wont start till 3500-4000 and thats also the same start point for your Vic Jr intake. Which may be fine if your planning on pulling 7500-8000 rpms. But if your using it to drive around, you wont be please with the hesitation, slow power build up and lost low end torque. The cfm rating doesnt mean anything about rich/lean. Its the same as talking about runner size, its saying how much air it can move. If its too big its like sucking through 5 or 6 straws. See how great your lungs enjoy that.

 

NosPony

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Nov 11, 2004

#19

• Nov 11, 2004

• #19

Thanks guys so a 650 cfm. Gas mileage isn't a concern. Its a stick so i will launch about 3000-3500 rpms.

 

NosPony

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Canton, Il

Nov 12, 2004

#20

• Nov 12, 2004

• #20

The info is helping thanks still cant make up mind though. Although, I have a better idea now what I want.