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Username Post: 500 CFM 4-Barrel Carb on 261?        (Topic#357234)
Five 0 
"14th Year" Platinum Supporting Member
Posts: 210
Five 0
Loc: Gainesville, TX
Reg: 07-02-03
07-15-19 08:17 AM - Post#2770734    

Hi all, I have an intake/exhaust/carb question for the experts here! After five long years, I have finally finished rebuilding my 1950 Chevy Styleline Special. The car is now equipped with a 261 engine (second engine, first on blew up), IFS, 4-wheel power disc brakes, 2004R trans, 3.42:1 posi '67 Camaro rear end, and new 12V, 10 circuit wiring harness and fuse box. Due to a "shop incident" I am now looking to replace the no-longer-serviceable Holley 5200 carb. After looking around at the alternatives, I'm contemplating replacing the existing setup - currently a 235 intake, 53-55 'vette dual exhaust, and Holley 5200 carb - with a 4-barrel Clifford intake (42-4500WH Single Carb Intake Manifold), Fenton headers, and a 500 CFM Edelbrock carb (AVS2 #1901). My main question is will the Edelbrock simply be too much carb for the engine? If the answer is yes, would a smaller 4-barrel carb (e.g., a 390 CFM Classic Holley Carburetor) be a more viable option? I have used Edelbrock carbs on other cars and am attracted to their ease of use, but don't want to put that carb on there if it is going to be "too much" for the engine. The engine is not "built" or raced out - it is newly rebuilt and bored at +.060 with a stock cam and uses a 235 "848" head (with proper steam relief holes added).



Thanks in advance for your time and assistance!

Mike



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1950 Styleline Special 2D Sedan
1956 Buick Century Riviera 2D HT
1958 GMC 3100 "Fleet Option"
1967 Camaro SS350 Clone
--

"You cannot help the poor man by destroying the rich."

~Semper Fi


 


2blu52 
"18th Year" Silver Supporting Member
Posts: 18960
2blu52
Age: 86
Loc: Montana
Reg: 03-12-02
07-15-19 08:50 AM - Post#2770736    
    In response to Five 0

Can not answer your question but that is one clean, sharp looking engine compartment!!!!!!!!

"PEACE IS THAT GLORIUS MOMENT IN HISTORY WHEN EVERY ONE STANDS AROUND RELOADING"

THOMAS JEFFERSON


 
Five 0 
"14th Year" Platinum Supporting Member
Posts: 210
Five 0
Loc: Gainesville, TX
Reg: 07-02-03
07-15-19 10:43 AM - Post#2770748    
    In response to 2blu52

Thanks 2blue52! Once I get this carb issue sorted, she'll be ready for the highways once again. I can't wait to drive her down the road once more - it's been a long five years without being able to go for a good cruise. I miss it - a lot!

1950 Styleline Special 2D Sedan
1956 Buick Century Riviera 2D HT
1958 GMC 3100 "Fleet Option"
1967 Camaro SS350 Clone
--

"You cannot help the poor man by destroying the rich."

~Semper Fi


 
54delivery 
Contributor
Posts: 111

Loc: Salem, OR
Reg: 11-19-13
07-15-19 11:18 AM - Post#2770750    
    In response to Five 0

Yes, that's a nice looking setup! I'm not an expert on what a basically stock 261 can handle for a carb either, but my guess is the Eddy 500 is too much, and would require more tuning than its worth to make it driveable. 390cfm would be better, I think.
However, the expert with a ton of experience in these matters is Tom Langdon.
http://www.langdonsstovebolt.com/
Check him out, get his recommendation and your 261 will be happy.



 
Mike JW 
"7th Year" Gold Supporting Member
Posts: 1374
Mike JW
Loc: Arroyo Grande, CA
Reg: 01-19-06
07-15-19 12:47 PM - Post#2770753    
    In response to Five 0

Hi Mike, I run a 390 CFM Holly on my 292, has a cam head work and its balanced. There is a formula for figuring out much carb to use. My guess is the 390 would be a better bet for your motor than the 500. Good luck whatever you do.
I found the formula: Cubic inches X RPM (safe max)
X.85 divided by 3456



Edited by Mike JW on 07-15-19 01:57 PM. Reason for edit: No reason given.

 
Lead sled 
Frequent Contributor
Posts: 1945
Lead sled
Age: 59
Loc: Walton,NY.
Reg: 11-04-09
07-15-19 01:30 PM - Post#2770757    
    In response to Five 0

This may able to help you decide???
http://4secondsflat.com/Carb_CFM_Calculator.html

Late yr model (Dec. 51 BelAir/ 52 trim), with a basically stock 67 Camaro SS350/295hp Turbo Fire Edelbrock 1405, Saginaw 4spd/355 geared 55/6 Chevy rear.2,1st place,and 1 top five award trophies so far
http://www.picturetrail.com/bris51deluxe


 
one4dad 
"6th Year" Silver Supporting Member
Posts: 1527
one4dad
Age: 76
Loc: Baton Rouge La
Reg: 01-17-10
07-15-19 04:03 PM - Post#2770774    
    In response to Five 0

If money is no object, have you considered a throttle body fuel injection system
Just a thought

Bill Wilson 50 styleline deluxe 2 door sold,- 51 styleline Deluxe 2 door ,'56 235 with dual carter webers on an Offenhauser intake, Fenton headers, 56 chevy rear end and 700R4 transmission.


 
carbking 
Senior Member
Posts: 1472
carbking
Loc: Missouri
Reg: 06-14-03
07-15-19 04:19 PM - Post#2770775    
    In response to one4dad

In a different lifetime, when Carter was building real AFB carburetors, the Performance Division of Carter suggested the following:

Modified Chevy six 235, 261, and 292 - 400 CFM
High performance Chevy 265 V-8 - 400 CFM
High performance Chevy 283 V-8 - 500 CFM

The 400 CFM was suggested for the 235, 261, and 292 simply because 400 CFM was the smallest Carter AFB. Note this was a recommendation for a performance street application with modified engine; NOT a recommendation for a trailered racecar, which would have been different.

Should you decide to heed the advice of Carter, the part numbers for the Carter 400 CFM was 9400s, which was superseded by 9410s. Both are quite difficult to find today.

Jon.

Good carburetion is fuelish hot air!

The most expensive carburetor you will ever buy.....is the incorrect one you attempt to modify!

If you truly believe "one size fits all", trying walking a mile in your spouse's shoes!


 
Five 0 
"14th Year" Platinum Supporting Member
Posts: 210
Five 0
Loc: Gainesville, TX
Reg: 07-02-03
07-16-19 07:11 AM - Post#2770828    
    In response to carbking

Thanks for all the input and guidance guys. It looks like moving to a 4-barrel carb isn't really a viable option at this point since the engine is essentially stock. I wasn't really thrilled by the idea making the change anyway 'cause I love the setup with the 'vette dual exhaust. I just need to find a good 2 barrel carb. I really liked the 5200 - it worked great. I will say that the throttle body fuel injection system is intriguing, I'm gonna look into that a bit more.

If anybody out there has a good Holley 5200 2-barrel they want to unload, I'd be interested - PM me :-). In the meantime, I think I'll talk to to Tom Langdon and find out what he suggests would be the best carb to run. I got the Holley 5200 from him 11 years ago and it did a great job.

1950 Styleline Special 2D Sedan
1956 Buick Century Riviera 2D HT
1958 GMC 3100 "Fleet Option"
1967 Camaro SS350 Clone
--

"You cannot help the poor man by destroying the rich."

~Semper Fi


 
DZAUTO 
Senior Member
Posts: 8710

Loc: Mustang, OK, USA
Reg: 12-25-99
07-16-19 08:10 AM - Post#2770834    
    In response to Five 0

I have a very close cousin who has a 1st series 55 pickup. It's fully restored and VERY minimally modified. The engine is a 261 bored/stroked to 283. The carb is a small AFB (I don't know the size) with Fenton headers. Runs like a Swiss watch and will pull stumps.
The transmission is a 4sp Saginaw and I built a 3.08 posi for it.







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carbking 
Senior Member
Posts: 1472
carbking
Loc: Missouri
Reg: 06-14-03
07-16-19 04:18 PM - Post#2770859    
    In response to DZAUTO

One of the more popular carburetor upgrades for a basically stock 261 is the Zenith carb used as original equipment on a G.M.C. 270. Will fit the original 261 intake manifold.

Jon.

Good carburetion is fuelish hot air!

The most expensive carburetor you will ever buy.....is the incorrect one you attempt to modify!

If you truly believe "one size fits all", trying walking a mile in your spouse's shoes!


 
dsacton 
"2nd Year" Silver Supporting Member
Posts: 1160
dsacton
Loc: Boulder, CO
Reg: 11-01-11
07-17-19 10:25 AM - Post#2770915    
    In response to Mike JW

Helped a friend put a Holly 650 on a 235 once. It was a lot of fun, but a complete waste of gas. My guess even 500 would be too large.

Scott Acton
1954 Chevy Bel Air 2-door
http://www.my54chevy.com


 
53Chevy 
Contributor
Posts: 280
53Chevy
Loc: Davenport, IA
Reg: 02-18-04
07-17-19 03:47 PM - Post#2770934    
    In response to Five 0

Something you might look into is a 3 barrel Holley Carb that Tom Lowe has for sale. I have one on my 53 BelAir with a bored 261 ci and 700r4 trans. I'm happy with it and get ok gas mileage and performs well. You run on a single primary until you step down and then you have 3 barrels. Just something to think about.



 
cbmkr56 
Silver Supporting Member
Posts: 1150
cbmkr56
Age: 63
Loc: Basehor Ks
Reg: 02-11-13
07-17-19 04:18 PM - Post#2770937    
    In response to Five 0

I am running a 450 Quick fuel HR series 4 bbl on my 261 with a Clifford intake, A little Jet tuning and it is Great. 18-20 on the Highway 60-70 mph ,85 up it drops to 16-17. That's with A/C too. Around 2200 rpm at 70 mph.



 
Stinky 
Senior Member
Posts: 1656

Loc: Whitewater, CO
Reg: 05-25-01
07-20-19 10:27 PM - Post#2771196    
    In response to cbmkr56

Oncst (like once), but many moons ago...I had a Buick Regal wagon w/a 4.1 (I think) V-6 in it....twas a stroked (I think), by GM, 231 V-6. I think that it was a 250 or 251.

Buick made them w/a Quadrajet.

It got crappy mileage...I dunno how much exactly. I sold it in '96? But, it memory serves me correctly, 19, on a good day, and never, not once, 20 mpg.

My '92 Astro van got that much w/a 4.3, pushing that box through the air.

The Qjet did not seem to be to big.

I ran a 350 Autolite carb on my 1751cc Honda, and a 500 on my 2000 Pinto...they had a good power curve (both motors were stock). I was running them in the dunes...a tank of gas a weekend is all that I know....way less than my boss' 2180 dual Solexes (big dif in cams there too).

I also experimented w/the same carbs on my 305...if my memory is correct, they did not run as good as 625 or Qjet. The best that, that truck ever ran was w/a 390...for a year or so, then 10 mpg, I fought w/it and fought w/it, and then put a 625 Ebrock on it. In the end...I wish that I woulda kept the Q-jet on it. I was chasing mpg, and performance was 2nd (although they all had about the same seat of the pants power)...looking back on it, after running the afb/Ebrock for a year or 2, I had to put a regulator on it, as I was fouling plugs w/to much fuel pressure...hmmm, I wonder how long did I have to much pressure. Did it go back to the 390? I link it to my fuel pump going out...possibly the new pump, being new, put out higher pressure. But, I have no idea of when it fit in the timeframe.

OK, enough already...there are 2 people, those that swear by Holleys...I swear at Holleys...don't even think, again, of putting a 390 on that motor, you'll be sorry. Just MHO.

Before I did that, I'd put a 350 or 500 Autolite or Holley on it...simple, simple is good. Or, a Carter 2 bbl from a 283. It will run fine.

Weber makes a prgressive 2 barrel. Redline sells them.

The fuel injection that was mentioned...you'll have 400 bucks in a new 4 bbl. This is $850.
https://www.summitracing.com/parts/sne-550-849



Edited by Stinky on 07-20-19 10:41 PM. Reason for edit: No reason given.

 
cbmkr56 
Silver Supporting Member
Posts: 1150
cbmkr56
Age: 63
Loc: Basehor Ks
Reg: 02-11-13
07-24-19 07:54 AM - Post#2771437    
    In response to Stinky

It has over 15K on it now and the mileage is what i said it was. You have to take in consideration how my engine is built and the drive train specs and tire size.
When i ran this car in the 70's i ran 2 large 1 bbl carbs and a 480 lift dual pattern X-14 crower cam with the same head work i am running now.
The trans was a M22 rock crusher with a 3.30 rear gear and 28.6 tire dia, I never saw over 14 on the highway most of the time 10 or under.
Now with the 4 bbl, with the rear 2 barrels not opening up until 70% throttle i am running on the highway on the front 2. I have went on many cruises and everybody keeps asking me when are you going to stop and get fuel and then how big is your tank it's stock 15 gallon.



 


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