Opinions on Carbs

My dad's friend has been racing dragsters since '95 and has been working on motors his entire life. My carb needed to be rebuilt and he offered to do it for me. When I was over at his house last night picking up the carb, he was talking about the 600 being too small for my motor and showed me a Carter AFB 625 with electric choke that he was willing to make me a deal on if I wanted. He was basically saying I could take it off his hands whenever I wanted. When I got home I did some research and from what I gathered Carter AFB turned into Weber and eventually Edlebrock copied the design for their current carbs. Since all of this most likely went down before I was even born, I had never heard of Carter AFB until the guy pulled the one out of a box and showed me. My initial reaction was that it looked exactly like an Edlebrock, which made sense after researching it.

So I was just wondering what your guys' opinions were on the AFBs. From what he was telling me, and what I have read, they are solid carbs.

Carter/Edelbrock/Webers are good carbs. They are very sensitive to dirt and heat. You'll notice many postings over on the VMF about fuel boil overs, hot hard starts, etc with Edelbrocks. That being said, I do not see any advantage of spending money on 25CFM.

I'll agree that a 600 is probably too small, but until you get your package sorted, I probably wouldn't worry about the carb. If the one you have works fine, then I'd run it for now.

In the future, I would look at a 750CFM carb for your engine.

Carter/Edelbrock/Webers are good carbs. They are very sensitive to dirt and heat. You'll notice many postings over on the VMF about fuel boil overs, hot hard starts, etc with Edelbrocks. That being said, I do not see any advantage of spending money on 25CFM.

I'll agree that a 600 is probably too small, but until you get your package sorted, I probably wouldn't worry about the carb. If the one you have works fine, then I'd run it for now.

In the future, I would look at a 750CFM carb for your engine.

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Well the one I've had my eye on since starting this project was the Holley 750CFM dual feed. That's actually what was on my car before the 600CFM. But some people that I've talked to say 750CFM is slightly large for 351ci. I was also thinking about a 650CFM, either the dual feed or double pumper.

What are most of the guys here running?

I've run 800cfm Holley DP carbs on my 351C-4V engines with great success. However, I run 4 speed transmissions and gearing was from 3.25 ~ 3.91, depending upon the car.

I see no issue with a 750 on a 351. If the motor is healthy and you don't have a 1200 rpm stall converter and 2.75 gears, you'll be fine.

I've run 800cfm Holley DP carbs on my 351C-4V engines with great success. However, I run 4 speed transmissions and gearing was from 3.25 ~ 3.91, depending upon the car.

I see no issue with a 750 on a 351. If the motor is healthy and you don't have a 1200 rpm stall converter and 2.75 gears, you'll be fine.

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With the setup in signature, what would recommend? Eventually I am going to put a T-5 in and I'm not sure what gears it has but I know they're aren't stock.

I have an Holley 850 DP

750 vs here

I have a quick fuel Q series double pumper and it works great.But I also am not running a stock cam and intake.But from what I have read oN this site and other forums the Cleveland can handle a 750 very easily {have you seen the intake ports on these heads. HUGE!!!!!}

i DON'T KNOW WHY IT'S BLACK BUT CLICK ON THE IMAGE TO SEE THE PICTURE

So how much of a difference is there in performance between the 750 double pupmer and the single?

The biggest difference will be in the lateral g forces when you accelerate.Double Pumper carbs have a slight advantage over a vacuum secondary for max acceleration. But dp carbs are a little harder to tune and less economical because you get a 4 shots instead of 2 everytime you stab the pedal

yes +1 on the double pumper outperforming the vs. I put a vs on my car because everyone on certain forums was telling me that would be the best for a street car. Apparently my version of a street car is alot different than theirs lol.

anything under 7000 hp = street car

Well, I think you guys have me sold on a 750CFM Double Pumper. I'm not worried about fuel economy, it's a '73 Mach 1, it's made to burn fuel. I'm not looking for my car to be a daily driver or anything, but that's not to say I won't drive it every day haha. I'm looking at carburetorsandmore.com, they seem to have the best prices on carbs. They've got an 800CFM Double Pumper for $295. Gonna shoot them an email and see what their inventory looks like. I'm still having some troubles with my 600CFM even after having it rebuilt so I might just go a head and spring for a new carb. Would like to get the 600 running so I can have a comparison, though. Plus, I've still got to pull the motor and do an overhaul on it so I'm not exactly ready for a new carb just yet.

Spring for a NEW carb, not one rebuilt by an unknown entity. It looks like he rebuilds them in his garage.

Summit has the 4779 Holley DP new for $434, or a Holley reman for $399

Yeah, after talking with the guy via email I'm not sure I want to deal with him anyways. He was dead set on the mechanical secondary carbs being "race only carbs".

Edit: Anyone heard of PacePerformance? They've got some good prices, too. $429 for the 4779S http://paceperformance.com/lookup.html?XYZ=&hidEngine=false&hidVehicle=true&hidSearch=true&hidBrand=false&tSearch=0-4779S

Yeah, after talking with the guy via email I'm not sure I want to deal with him anyways. He was dead set on the mechanical secondary carbs being "race only carbs".

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HA omg.

i'm using a holley 750DP, its fine i like the adjusability.

one thing i'm not a fan of compared to the 650DP is the use of meter plates instead of jets for the secondaries. it made tuning more of a pain for me.

i liked the 650DP cause everything was interchangeably from the primaries to the secondaries and it was "cheaper" for me to mess around with my cruise settings.

i feel my cruise is too rich but i can't really lean it out anymore cause of the meter plates being limited in selection and i don't want to spend the money on an aftermarket Tunable plate cause i think its overkill.

the cleveland runs way better with a 750 then a 650 I have a 770CFM i wanted to try New in Box but i never got around to bolting it up and trying it.

personally i would of loved it if my engine would of liked the 650, but i found my butterflies were open too far to maintain a good mixture my transition slots were exposed even after i tried to bump open the secondaries some more, at that point i made the mistake of drilling holes in my 650 butterflies for more airflow at idle that lead to other problems, i wanted to keep that 650 since the vacuum signal at low rpms was higher i figured the throttle would be more responsive but there were so many other issues that when i bolted the 750 up most went away.

a 351 seams to do best when you dump more fuel into it. i've noticed that as well, lots of Lean misfire in the mid throttle range on a cleveland.

well even with the 750 dp leaned as far as i'm comfortable with around town its like 8-12 mpg on the highway however i have gotten 18-20mpg on a 130 mile trip with some heavy traffic i managed 16mpg. i'm comfortable with a 200+mile limit before i need gas. its worse in the winter since i keep the mixture richer to compensate for the cold weather.

Yeah, after talking with the guy via email I'm not sure I want to deal with him anyways. He was dead set on the mechanical secondary carbs being "race only carbs".

Edit: Anyone heard of PacePerformance? They've got some good prices, too. $429 for the 4779S http://paceperformance.com/lookup.html?XYZ=&hidEngine=false&hidVehicle=true&hidSearch=true&hidBrand=false&tSearch=0-4779S

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personally I would rather pay a few more dollars from Summit or Jegs and have a warranty/return option.

What about a Reman from Holley's eBay store? Might be able to catch it for cheap bidding on it.

http://cgi.ebay.com/ebaymotors/Holley-0-4779s-750-Double-Pump-Carb-Holley-4150-_W0QQcmdZViewItemQQhashZitem53e4c46d98QQitemZ360320363928QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories

I'd love to just pick up a brand new one from Jegs or Summit, but I'm on a pretty tight budget. Being a broke college student is no fun haha.

I'd do the Holley refurb with a 90 day warranty long before i ever went to a backyard rebuilder.

i'm using a holley 750DP, its fine i like the adjusability.
one thing i'm not a fan of compared to the 650DP is the use of meter plates instead of jets for the secondaries. it made tuning more of a pain for me.

i liked the 650DP cause everything was interchangeably from the primaries to the secondaries and it was "cheaper" for me to mess around with my cruise settings.

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Double pump carbs all have a secondary metering block, I've never seen one with a plate and I don't think the rear accelerator pump would clear the baseplate either. What's the list # on the air horn?

At cruise, all fuel comes from the primary bowl and block, nothing from the secondary, unless you have a 4-corner idle circuit carb. Even then you're still on the primaries. A big "issue" with DP carbs is the primary jets are set rich with a leaner power valve setting. Ten minutes with jets and a drill fixes that issue.

FWIW, just because it's an old car with a big carb doesn't mean it has to be bad on fuel. I'm a big proponent of getting the most MPG out of your classic. These cars respond very well to simple and cheap mods.

Example: 1971 Cougar M-code - @4000lbs with me in it..

Initital MPG : 8mpg

Change junk 4300 carb to 800DP : 11mpg

Tune up and tweak timing: 13mpg

Brake job, new rear axle brgs: 14mpg

Change factory flex for clutched fan: 16mpg

I also had a 72 T-bird with a 429-4V that got 17mpg.

What about a Reman from Holley's eBay store? Might be able to catch it for cheap bidding on it.

http://cgi.ebay.com/ebaymotors/Holley-0-4779s-750-Double-Pump-Carb-Holley-4150-_W0QQcmdZViewItemQQhashZitem53e4c46d98QQitemZ360320363928QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories

I'd love to just pick up a brand new one from Jegs or Summit, but I'm on a pretty tight budget. Being a broke college student is no fun haha.

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I do understand "Broke" thats what I've been since I started this project. But hey on a brighter note I'm keeping Don's (OMS) kids in school.