(Disp. x RPM / 2 ) / 1728
Engine Displacement x max RPM divided by 2 (because it takes two full
revolutions to equal the displacement) and divided by 1728 (to convert
from cubic inches to cubic feet).
Take a 351 cu.in engine, times 5500 RPM (street use) and plug that into
the formula and you get 558.59375 SFM throughput. (602cfm @ 6K RPM)
So a 600 CFM carb. is more than adequate.
Cheers -
Michael
Dan O'Reilly wrote:
> 730-750 strikes me as over-carbureted for a 351, isn't it? The
> recommendations I've been hearing are in the 600cfm range.
>
> At 12:22 PM 5/19/2009, Paul Stephens wrote:
>
>> --- In classicmustang@yahoogroups.com, Dan O'Reilly <dano@...> wrote:
>>
>>> OK, I have the feeling that asking this is like trying to discuss religion
>>> or baseball, but here goes anyway. Looking for the relative merits of a
>>> Holley carb vs a comparable Edelbrock. This is for my '71 Mach, 351C
>>> motor. I realize that Holleys had a reputation for blowing out power
>>> valves, but their literature all seems to indicate they have "power valve
>>> blowout protection" to remove this possibility now. The Holley strikes me
>>> as easier to hook up to my existing tranny kickdown & throttle cable.
>>>
>>> I had almost decided on the Holley (model 80457), but am rethinking
>>>
>> this in
>>
>>> light of a trusted Mustang restorer last weekend telling me how little
>>> trouble they have with Edelbrock vs Holleys.
>>>
>>> Your thoughts (sans emotion, please)?
>>>
>>> ---
>>>
>>> Dan O'Reilly
>>> 1971 Bright Red Mach 1
>>> 2002 Black Deluxe Convertible
>>> Colorado Springs, CO
>>>
>>>
>> Dan,
>> The Edelbrock carb is probably more trouble-free just because it is not as
>> easily tunable as the Holley. There are a lot of "Holley Experts" that
>> swap throttle bodies and cut choke housings and then complain that their
>> Holley is junk.
>> Both are good carbs right from the box - IF they are properly selected for
>> the application. The Holley is more easily tuned for a specific use and
>> application but for most cars it is a bolt-on and go carb. For street use
>> a carb that is rated in the right CFM rating with a vacuum secondary is
>> the best way to go. For the strip a double pumper in a slightly larger
>> size will give the top end performance.
>> The biggest draw-back for the Edelbrock is the "air valve" secondary
>> set-up. It is nothing more than a spring loaded choke plate installed to
>> make sure the secondaries pull fuel when they are opened. This one feature
>> is a real restriction in a performance application.
>>
>> In your application a Holley 730 - 780 CFM vacuum secondary 4150 would be
>> the ideal carb - depending on use. I am assuming it is primarily a street
>> cruiser. Before deciding that poor running is a carb issue work over the
>> tune-up first. Most often "carb" issues are just poor tuning. If your
>> application is street only and you want good manners then look at the
>> Street Dominator series of Holley. They are good carbs for that
>> application and are completely plug and play.
>>
>
> ---
>
> Dan O'Reilly
> 1971 Bright Red Mach 1
> 2002 Black Deluxe Convertible
> Colorado Springs, CO
>
>
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