what carb

[michael69]

What is the best carb to run on a mostly stock 302 engine? A vacuum or mechanical secondary? And would a 600cfm be about the right size. It will have an auto transmission also. Thanks

[hotrodfeguy]

I would go Holley 390-450 CFM on a stockish 302 in a truck

http://www.summitracing.com/parts/HLY-0-8007/

http://www.summitracing.com/parts/HLY-0-90470/

http://www.summitracing.com/parts/HLY-0-1848-1/

[Dragon]

A 302 at 5000 rpm with stock 4V manifold and no cam is at a maximum 85% Volumetric Efficient. Given those 3 numbers At max rpm you need 371 so I would go with the for future minor engine changes. A 390 would hold you back in the future.

[sideoilerfe]

371 CFM he might as well keep the 2V autolite. Besides, 302's like RPMs anyway so, a 500 would be pretty good for a stockish motor IMO.

[michael69]

The motor has been rebuilt pretty much stock with a rv cam and has headers, it has an edelbrock performer intake an edelbrock carb now I think its a 600. I just don't like the edelbrock and wanted to change to holley just didn't know where to start as for size. THANKS

[george worley]

A 600 cfm should be about right and will work good with future engine mods. as long as you aren't building a full out race engine.

[cdeal28078]

I myself think a lot of people use too large a carb. I would go with the 450 at most. It is a great little carb. A lot of people putting 4v's on the 300's use the 350 cfm's and like them but they turn less RPM's, Heck, I am running an 1850 Holley that is 600 CFM on my mild low compression 460 in my 71 F100 and it runs nice and clean with great throttle response
clint

[bb429power]

A 600 cfm should be about right and will work good with future engine mods. as long as you aren't building a full out race engine.

Took the words right out of my mouth. I have heard that the holley 600cfm carbs are crap. But I have one on a stock cammed 302 and it runs great. Its a 4160 series carb.

[Dragon]

Yeah the Holley 1850 or 600 cfm carb since 1992 is no more crap than any other Holley. All Holleys had a problem with backfiring blowing the power valve before 1992.

[fitzwell]

for most applications, the old 1850 works like a champ. If you can find a 4180 series holley ( 84-85 351H.O. pickups) grab it. Put a Holley kit in it and drop the jets to about a 58-59. Runs like a champ & gets killer fuel milage, if you can keep your foot out of it

[Dragon]

Or take any Holley and put a two stage power Valve in it and you don't have all the smog ports and frozen in place idle mixture needles.

[fitzwell]

Or take any Holley and put a two stage power Valve in it and you don't have all the smog ports and frozen in place idle mixture needles.

You also loose the annular discharge boosters.

Ports off the float bowls are capped, or plugged with a small freeze plug, cap the vac ports you don't need, use the correct one above the throttle plates & you're good to go.

Idle mixture caps are no match for a die grinder


as always,

[Dragon]

You also loose the annular discharge boosters.
:

How do you lose the boosters?

[fitzwell]

You also loose the annular discharge boosters.
:

How do you lose the boosters?

You loose the advantage gained by having annular discharge boosters

4160 style carbs have a "standard" booster, single hole for fuel discharge. 4180 series uses "annular discharge" boosters. Several small holes in the booster for fuel.

Guess i'm too lazy to type, sorry for the "cut & paste", but this covers it pretty well.. from a car craft tech article.


"In the early days of performance carburetors, boosters projected straight out from the upper portion of the carburetor barrel above the venturi. Later, downleg boosters were used to place the trailing end of the booster closer to the highest velocity point in the venturi. Both of these boosters employ a single fuel discharge point, relying on the shearing effect of high-velocity air moving past the booster to atomize the fuel.

Finally, there is the annular booster, which is slightly larger in diameter than the downleg and employs a series of small discharge holes drilled into the inside circumference of the booster to improve fuel atomization. This annular design accomplishes several things. At lower engine speeds, slow air speed creates a weak signal, which reduces the amount of fuel moving through the booster. An annular discharge booster's multiple holes offer many points for the fuel to enter the venturi as opposed to a single discharge point. At lower air speeds, this offers measurable advantages, especially when combined with the annular's better signal strength. This is important for situations where large-volume carburetors are used in conjunction with a long-duration camshaft. With a weak manifold-vacuum signal at idle, annular-discharge boosters can greatly improve throttle response and driveability.

Of course, annular boosters aren't exactly a free ride. First, the annular's larger size presents a slight airflow restriction, reducing the carburetors' total capacity compared to smaller downleg boosters. Second, with all other variables equal, an annular booster creates a stronger fuel signal, generally requiring smaller jet sizes. There are exceptions to this rule, but adding annular-discharge boosters requires smaller main jets and larger high-speed air bleeds compared to the downleg style.
"

[Dragon]

Okay that threw me. The 4180 was a blend of Autolite and Holley technology. It would be nice if Holley embraced annular discharge on all the carbs.