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Old 06-21-2013, 01:33 PM
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Deciding on a Carburetor

I'm close to needing to purchase a carb for my newly rebuilt engine. I'm looking at picking up a 600-cfm Holley vacuum secondary carburetor (0-1850s), but wanted to check with people who have a lot more knowledge about the subject than I do.

Specs:
  • sbc 350,
  • stock crank
  • Hydraulic flat tappet cam & lifters, 274 duration, .450 lift,
  • (Cam likes 9:1 and higher compression)
  • Vortec heads and intake
  • Automatic transmission (th350) 2.52/1.52/1.0
  • Ford 8.8 Rear, 3.73, 31 spline, limited slip
This is going to be a street machine. Also, will I need to purchase a metering block?

Thanks,

-A

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Old 06-21-2013, 01:35 PM
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I like the double pumper carbs and think you would like a 650 double pumper
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Old 06-21-2013, 03:12 PM
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Any opinion on removing the choke horn?
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Old 06-21-2013, 03:21 PM
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I see no reason to modify the choke horn.You will need a cable for the choke if you require a choke in your area.I dont have a choke in my carb,I drive mostly in warm weather,and I just drive the car easy when cold
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Old 06-21-2013, 03:45 PM
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I'm digging the new 625 Street Demon.
New Demon "Street Demon" 625cfm carb
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Old 06-21-2013, 03:56 PM
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Difficult decision. I have been going back and forth between Holly and Edelbrock and it seems that had better luck with the Edelbrock. This is been going on for years. I wasn't so cheap Id by a demon
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Old 06-21-2013, 04:28 PM
How fast is fast enough?
 
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The street demon 625 isn't a bad carb for a street engine. IMO a dp carb is not a good idea if its primarily for street use.
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Old 06-23-2013, 01:31 PM
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I have a holley 600 vacuum secondary on my 350 with dart shp heads and lunati 219/227 @ 50 515/530 lift hydraulic roller cam with 9 to 1 cr and it runs very awesome with decent mileage and give awesome throttle response sitting in a chevy s10 with 3.42 rear gears and a turbo 350 with 2200 stall.

I did have a 650 double pumper on my more wild 350 with dart iron eagle 200cc fully ported heads with a 231/239 @50 535/550 lift lunati voodoo hydraulic roller cam with 3.73 rear with a turbo 350 3500 stall and I loved it but the double pumper was a little rich and fuel mileage was horrible but I understand my combo is not fuel mileage type of motor but I wanted to get as much as I could get and I got a proform/quick fuel vacuum secondary and it runs just as good and does better for street manners.

double pumpers can be made to work but they will always run richer then a vacuum secondary unless you really know how to really fine tune a carb and we are not talking about jet changes only.

I vote the 1850s holley as it will give better power then edelbrock and allow more ultra fine tuning then the edelbrock but they both have there plus and minus areas.

I used to run edelbrock but after going over to holley I never looked back. You can also consider a Qjet as it offers plenty of breathing and also they will give better mileage then any carb out there from what I have read and heard on these boards.

They are just a little more tricky to tune then say a holley or a edelbrock unless you know them well.
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Old 06-23-2013, 06:56 PM
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Mileage is a good point. I'd prefer to not have to fill the tank every two blocks.
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Old 06-23-2013, 09:03 PM
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Eddys are more reliable then holleys but im a holley person.
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Old 06-23-2013, 09:36 PM
How fast is fast enough?
 
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Quote:
Originally Posted by andrewakessler View Post
Mileage is a good point. I'd prefer to not have to fill the tank every two blocks.
Edelbrocks tend to be a little better on mileage than holleys. It the new 625 street demon is a better carb design than either IMO. I'll likely never run them as I switched to fuel injection but if I had to run a 4bbl carb on a mild street 350 the street demon would be my first choice.
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Old 06-24-2013, 02:17 AM
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If you want performance and gas mileage I'm likin the tuned port system I put on my 85 monte. 19% horsepower gain bolt on! I took mine from an 86 iroc but they do offer aftermarket ones also and they come with instructions! The iroc I got mine from didn't offer instryctions at all! LOL! My monte with the stock 305 HO is getting around 23 mile to the gallon interstate and 16-18 round town plus its not a slobbering cylinder washing carb. Carb I would suggest would be a 650 double pumper or like the other guys suggested the street demon. I really dig the street demons. responsive and just overall workmanship over the holleys is superior. My son is currently running a 950 race series holley on his Late Model roundy round car. The race series and HP series holley spent a little more time on machining and tuning far more superior than the production line crap you buy at Oreilly's!
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Old 06-24-2013, 07:38 AM
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One can never go wrong with a Q-Jet.








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Old 06-24-2013, 08:10 AM
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I would vote for a Q-jet, too. But that said, unless you're prepaired to do some tuning that requires the carb to be disassembled- possibly several times- you might not want to use a Q-jet. But once they're right, they're superior to the other carbs because of the sensitive primaries and the ample secondaries that allow the carb to meter well on almost any engine size.

Next to the Q-jet I would use a Holley vacuum secondary carb in the 600-750 range. Holley because of the amount and depth of knowledge that's readily available for tuning/repair, and the parts availability that makes repair possible- Holley parts are as near as the local parts house. The exact carb would depend on how the engine was to be used, etc.

A page w/some info that might be useful is here.

Good luck.
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Old 06-24-2013, 10:02 AM
How fast is fast enough?
 
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Quote:
Originally Posted by cobalt327 View Post
they're superior to the other carbs because of the sensitive primaries
This has NEVER been proven. A quadrajet can be made to work as well as any other carb but there is really nothing to think that they are in someway superior to any other carb.

Regarding primary sensitivity you can have two Holley 600's that to the untrained eye look identical, but can have VERY different metering characteristics. I love the "well the primary bores are smaller" argument- as if that made a damn bit of difference.


The Demon 625 looks like it has the best design characteristics from Holley, Rochester, and Edelbrock- I have never used one- but I can see the advantages in certain design aspects. You'd also be dealing with a brand new core, not an old refurbished one (as in quadrajets). Parts availability is better with holley's but they may be the hardest to actually tune, the Edelbrocks and 625 demon are the easiest.

Really, they can all be made to work and none are far above and beyond the rest, but some are easier to use and have a better design to work with.

Swapping to EFI is obviously better than any of these choices, but is admittedly a little more complicated to install (though a hell of a lot easier to tune).
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