Carburettor Size

[hank63]

[DEEPNHOCK]

Most Yankee's are running the Edelbrock AFB carb for ease in tuning and great driveability. Also has the right bolt pattern for a Stude 4 barrel manifold.
http://www.edelbrock.com/automotive_...erformer.shtml
Some good reading can be had by downloading their carb application guide, available at:
http://www.edelbrock.com/automotive_..._app_chart.pdf

500 cfm for a 259 V8, and a stock 289 V8 engine

P/N# 140314031406*
600 cfm, square-flange, electric choke (non-EGR) w/ EnduraShine finish #[u]14064</u>* (OOoooohhhh shiney!)




DEEPNHOCK at Gmail.com
Brooklet, Georgia
'37 Coupe Express (never ending project)
'37 Coupe Express Trailer (project)
'61 Hawk (project)
http://community.webshots.com/user/deepnhock

[Dick Steinkamp]

quote:Originally posted by hank63

Hmmmm....I'm probably reading the above wrong, but the carb WILL flow 100% of its RATED CFM (dry), if you suck on it hard enough (or blow through it hard enough). Per your example, a 289 CID engine (at 100% volumetric efficiency) will flow a 500 CFM carb at max at 6000 RPM.

http://www.csgnetwork.com/cfmcalc.html



Fitting an oversized carb will result in poor low speed performance driveability issues), a "bog" when feeding in too much throttle from a start, and poor fuel economy.




Dick Steinkamp
Bellingham, WA

[Mike Van Veghten]

Dick...most of what you say is correct, and more would be happier if they stayed closer to 500cfm, for stock and mildly modified 259's and 289's, (The BG carburetor line now has a 525cfm carb.).

Except the "bog" part isn't totally on track. If not tuned correctly, a "bog" can be found with a two barrel carb. An Edelbrock 1403/1406 can have/develop a bog if not tuned correctly. Conversly, a 750cfm carburetor can be tuned to "seemingly" work just fine on a stock 259 engine. It'll just be down on milage, power and driveability. If tuned correctly...no bog will be present..

Now I suppose if one were to install a Holley Dominator of the 1050cfm or larger..."that" most likely produce a bog that wouldn't be tunable...but that would be a real chore and quite a few bucks to buy and install!

Mike

[studeclunker]

Mike and Dick,
I installed a 650 CFM Holly on my Champ (259) because that's all I had on hand. Is there a way to work with this? I can see what you mean by stumbling on a start. It does. Right now it's necessary to work with what I have on hand. Kinda short on cash...


Lotsa Larks!
K.I.S.S. Keep It Simple Studebaker!
Ron Smith
Where the heck is Lewiston, CA?

[Mike Van Veghten]

The 650 Holley is a big carburetor for this engine.

That said, nice thing about the Holley is the tuneability.
If you have a stumble...there are several places to look -

1. Idle mixture screws correctly adjusted
2. Throttle blade angle within a usable location within the transfer slot.
3. Accelerator pump cam swap.
4. Accelerator pump nozzle swap.
5. Power valve sizing correct (vacuum wise).
6. Ignition timing.

These all have to work together.

Save your money and get something a little smaller. In the mean time, have fun working the Holley out.

Mike

[hank63]

One problem with oversized carbies is the air flow velocity. When too low, fuel vaporisation isn't what it should be, leading too poor response and chronically bad fuel consumption.
I expect that can be improved with special manifold and hi-rpm driving, neither of which comes cheap.
I'd stick with max 500cfm. If I had a bigger carbie, I'd try to swap it (if cost is an issue).
Mind you, if cost truly was an issue, we should all drive little 4-cylinder egg beaters made up of plastic and electronics (and replace 'em every 2-3 years).
/H