Holley spreadbore carbs
Melting Slicks
Joined: Dec 2000
Posts: 2,635
Likes: 0
From: Union Ontario
I ran a spreadbore holley for a few years on my 350 and it was great, a little sluggish on the bottom end(it was too big) but great on the top end. Just remember they are Mechanical secondaries on the spreabore- q-jet replacement series.
If you can get a great deal like I did on a spreadbore Holley do it, but if not buy a square bore Holley and an adapter plate for it. I have heard that the squarebore carbs are much better.
If you can get a great deal like I did on a spreadbore Holley do it, but if not buy a square bore Holley and an adapter plate for it. I have heard that the squarebore carbs are much better.
Advanced
Joined: Sep 2004
Posts: 70
Likes: 0
From: Ontario
I put a Holley Street Avenger on mine, works great.
I tried 2 different Quadra Bogs first, but the engine was sluggish with them.
Street Avenger woke it up, moves like a bat out of hell now. 670cfm model
I tried 2 different Quadra Bogs first, but the engine was sluggish with them.
Street Avenger woke it up, moves like a bat out of hell now. 670cfm model
Le Mans Master
Joined: Jan 2003
Posts: 6,575
Likes: 1
From: Tuttle OK
Cruise-In VIII Veteran
Originally Posted by MikeC
IIf you can get a great deal like I did on a spreadbore Holley do it, but if not buy a square bore Holley and an adapter plate for it. I have heard that the squarebore carbs are much better.
Le Mans Master
Joined: Jan 2003
Posts: 6,575
Likes: 1
From: Tuttle OK
Cruise-In VIII Veteran
Holleys web info on the carb...
Features
Model 4175 spread bore
Q-Jet/Thermo-Quad replacement
Universal calibration
Vacuum secondaries
Vacuum for: PCV,EGR, power brakes, distributor, air cleaner & canister
Electric choke
Power valve blow-out protection
100% wet-flow tested and street calibrated
Features
Model 4175 spread bore
Q-Jet/Thermo-Quad replacement
Universal calibration
Vacuum secondaries
Vacuum for: PCV,EGR, power brakes, distributor, air cleaner & canister
Electric choke
Power valve blow-out protection
100% wet-flow tested and street calibrated
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Instructor
Joined: Jan 2002
Posts: 243
Likes: 1
From: Knoxville TN
Well tommorrow, I'm going to get the carb back from rebuilder. Then If I have the time to put it on, I'll try it.
Whether, I'm happy with it or not, I'll keep the 7040202 carb since it belongs with the car.
I'm surprized, no one says, keep the quadrajet.
Is the holley a better street carb?
Also, spoke with a brother-in-law, he says go holley, easier to rebuild, but recently he brought a new holley (instead of rebuilding old holley), then his car was running rich, so it needed a new holley (warranty replaced).
I'm guessing a 650 is all that needed for a steet driver, can a divorce choke be added or is electric or manual the only options?
Whether, I'm happy with it or not, I'll keep the 7040202 carb since it belongs with the car.
I'm surprized, no one says, keep the quadrajet.
Is the holley a better street carb?
Also, spoke with a brother-in-law, he says go holley, easier to rebuild, but recently he brought a new holley (instead of rebuilding old holley), then his car was running rich, so it needed a new holley (warranty replaced).
I'm guessing a 650 is all that needed for a steet driver, can a divorce choke be added or is electric or manual the only options?
Advanced
Joined: Sep 2004
Posts: 70
Likes: 0
From: Ontario
Originally Posted by 78whtshark
Well tommorrow, I'm going to get the carb back from rebuilder. Then If I have the time to put it on, I'll try it.
Whether, I'm happy with it or not, I'll keep the 7040202 carb since it belongs with the car.
I'm surprized, no one says, keep the quadrajet.
Is the holley a better street carb?
Also, spoke with a brother-in-law, he says go holley, easier to rebuild, but recently he brought a new holley (instead of rebuilding old holley), then his car was running rich, so it needed a new holley (warranty replaced).
I'm guessing a 650 is all that needed for a steet driver, can a divorce choke be added or is electric or manual the only options?
Whether, I'm happy with it or not, I'll keep the 7040202 carb since it belongs with the car.
I'm surprized, no one says, keep the quadrajet.
Is the holley a better street carb?
Also, spoke with a brother-in-law, he says go holley, easier to rebuild, but recently he brought a new holley (instead of rebuilding old holley), then his car was running rich, so it needed a new holley (warranty replaced).
I'm guessing a 650 is all that needed for a steet driver, can a divorce choke be added or is electric or manual the only options?
Quadrajets are for better fuel economy, but Holley's are better for performance.
Melting Slicks
Joined: Dec 2000
Posts: 2,635
Likes: 0
From: Union Ontario
Originally Posted by SHAKERATTLEROLL
If you want more CFM you can get the Holley 6213AAA which is a 800 CFM Double Pumper.
I never knew that they had the spreadbores in Vac. secondaries..
Le Mans Master
Joined: Oct 2002
Posts: 5,714
Likes: 6
From: Silver City NM
St. Jude Donor '05-'07
Originally Posted by SHAKERATTLEROLL
If you want more CFM you can get the Holley 6213AAA which is a 800 CFM Double Pumper.
Dep
Racer
Joined: Jul 2003
Posts: 460
Likes: 18
From: Conroe, TX
FWIW, I ran the spread bore Holley model #6910 on my '71 Trans Am 455 H.O. for awhile, and it was a great carb. It was an 800 cfm DP, and the damn thing was HUGE! With its full size bowls, it required some serious re-working of the drop base aircleaner housing since the float bowl adjustment screws were "pushed out" by the larger spreadbore center section. Great carb though. . . I later upgraded to a 953 cfm Barry Grant and finally a 1000 cfm Race Demon after going solid roller.
Its hard to beat the basic Holley DP design for its simplicity and effectiveness IMHO. . .
Its hard to beat the basic Holley DP design for its simplicity and effectiveness IMHO. . .
Melting Slicks
Joined: Nov 2003
Posts: 2,668
Likes: 118
From: St. Charles Mo
CI 5 & 8 Veteran
Originally Posted by DJ Dep
I just checked...the 800CFM is discontinued. A shame...it had the desireable center pivot floats, which are real easy to set 
Dep
Dep
Any idea what they are going for these days?Bullshark
Pro
Joined: Oct 2003
Posts: 565
Likes: 0
From: I'm bleeding, making me the victor!
Holley carbs are my personal fave. Easy to tune and the vacuum secondary models are very 'forgiving' in regards to your engine size, combo, etc. Not to mention you can get perfomance parts for them at almost any parts house. They get a little tricky to tune when you venture into the mechanical secondary world, a.k.a. the double pumpers. You will need intermediate to good tuning skills to get these set up just right in some cases. Stick with a vacuum sec. model......VERY good performance and ease of operation.......you will not be disappointed!
Melting Slicks
Joined: Nov 2003
Posts: 2,362
Likes: 1
From: San Antonio TX
Sorry for the wrong information on the 6213AAA Holley I had no idea they were no longer produced. I have run a couple of them and found them to be fantastic carbs. I ran one on a little tiny 355 SB turning 85OOrpm years ago. Got great milage and had go to with as one said those huge secondaires. I used to use them as replacements for Quadrajets on Big Block cars since they were a bolt on. But as another person said they were huge. If I remember right they were right at 13in long.
Le Mans Master
Joined: Oct 2002
Posts: 7,098
Likes: 378
From: Las Vegas - Just stop perpetuating myths please.
I just couldn't resist this post. :o
The Holley is a simpler carb and its typical problems are well know and easy to diagnose. The big advantage with the vac sec is on boats where the sec remain steady while riding the waves. And they would work just fine on any street engine as a Qjet replacement. Kinda like choosing between a Ford, Dodge or Chevy here. Just be aware the speadbore is a different type of Holley and not much will interchange with the squarebore Holleys.
The Qjet is more unique and sophisticated and takes some study to make it a performance carb. With triple pri venturies it is very sensitive to low speed/air flow throttle changes - great for street use. Also the sec air vlv allows a big 750 cfm carb to work on a great range of engine sizes - 305" to 454". But it also has some problems unigue to the Qjet - linkages, air vlv spring adj, internal leaks.
If you really what max performance the Demon carbs are the out of the box winners but that doesn't mean that a Qjet can't be made to match it.
cardo0
The Holley is a simpler carb and its typical problems are well know and easy to diagnose. The big advantage with the vac sec is on boats where the sec remain steady while riding the waves. And they would work just fine on any street engine as a Qjet replacement. Kinda like choosing between a Ford, Dodge or Chevy here. Just be aware the speadbore is a different type of Holley and not much will interchange with the squarebore Holleys.
The Qjet is more unique and sophisticated and takes some study to make it a performance carb. With triple pri venturies it is very sensitive to low speed/air flow throttle changes - great for street use. Also the sec air vlv allows a big 750 cfm carb to work on a great range of engine sizes - 305" to 454". But it also has some problems unigue to the Qjet - linkages, air vlv spring adj, internal leaks.
If you really what max performance the Demon carbs are the out of the box winners but that doesn't mean that a Qjet can't be made to match it.
cardo0