RE: carb size further - 670 cfm Holley?

["Dennis C." <dennis.2914@xxxxxxxxx>]

Don,
I have been reading and saving all of your messages concerning carbs and 
their setup.

I have a street 63 SF with a 383 4-speed.  When I got my carb last year 
I sized it on the Holley site and it came up with the 670 cfm Street 
Avenger.  It seems to run well but really does not have the punch that I 
expected from the 383.  The only adjustments I have made are to the air 
bleeds.

Did I get the wrong carb for street use?  This car will never see a drag 
strip.  I'm sure I can pass this carb on and easily replace it with a 
750 cfm.

Any thoughts on the 670 Street Avenger or why Holley seems to undersize 
their recommendations?

Thanks
Dennis C.

Don Dulmage wrote:
> 
> 
> I should have finished thos last week but I had so much going on I 
> couldnt . sorry.
> The question comes up in ones mind that carb sizing is for racing of 
> full perfomane. What if one just wants carb for an engine that will 
> never see 6000 RPM. Should you use a differeent formula? 
> Actually it is not necessary. because carb sizing is focused on the 
> whole rpm range and proper carb operation at low speed . That is because 
> any engine will operate a carb at high speed. That is never a r problem. 
> even a 1050 dominator on a VVW flat four would be possible at 2500 RPM . 
> It is the low speed perfomance that we are always concerned about and 
> the carb sizing formulas mine or the complcated math version are picking 
> the largest size of carb practial that will still drive normally and 
> properly at normal low speed so you can use the same formula even if you 
> intend to drive like yer granny. . If any are having trouble with a carb 
> i would try to help if you need it . Email me direct. Like i said before 
> a lot of so called carb problems are actually not but canbe traced to 
> ignition.  Otherwise they can be poor chi oices well intended but made 
> because of a misunderstanding of how a carb functions.  Here would ba a 
> typical examle and I hear this often. 
> I have a 750 on my car but the guy who did jetted it down to a 600. 
> WRONG!!!!!!!!!!!!!!!
> Jetting in all carbs is designed for normal mixture  (ca 13 to 1 air 
> fuel ratio which means we mix 1 pound of fuel for every 13 pounds of 
> air. and it doesnt matter if it is a 350 a 500 a 1050 or bigger. the 
> mixture should be the same) Anytime you need to change aholey more tan 4 
> jet sizes even for racing you need to ask yourself what is wrong. 
> Something certainly is since 4 jet sizes would bring any holley carb 
> well into the 12 to 1 afr range and there is never anyreason to go more 
> than that.
> maybe i will touch on Power valves next time. They are also 
> misunderstood and a lot of well intentioned balck magic that is out 
> there really messes up otherwise good set ups. Carbs are reall very 
> simple . if someone talks like they are not avoid him. A fourbarrel 
> holley for instance has for internal parts that can be serviced 4 jets, 
> one or two power vavles. 2 or 4 idels screws and two floats with needle 
> valves.It may have one accel pump and nozzle with accompaning check 
> needle(Vacum sec ) or two (double pumper) that is it . I know some race 
> carbs have replacabe air bleeds etc butI would avoid them  as they are 
> just an invitaion to trouble on te lost highway of hot rod life and 
> rarely of ever need to betouched unles you are running in the top ten of 
> prostock. 
> Don
>   
> Author of
> Return to Deutschland (True Adventure)
> Old Reliable (Mopar)
> http://altonapublicschool.faithweb.com/
> 
> http://seniordragster.bravehost.com/index.html
> [Non-text portions of this message have been removed]
> 


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