500 cfm 2 bb

[hotrod ford]

have any of you guys seen this carb that holley makes? it is a 500 cfm 2 bb. that is quite alot for a little carb. i think beside a stock look you could use that a hopped up cam, good heads and a hi flow fuel pump and you could have a stout 360. you would'nt need to change to a 4bb and have to change your intake for more hp.

[My427stang]

They are rated differently than a 4 barrel. I think I heard the estimate is 2 barrel rating x .78 = comparable 4 barrel. That would make it about a 390 carb.

That rating makes sense as it is dimensionally 1/2 of a 750 / 780 4 barrel carb.

With that being said, its a VERY good carb. When my 71 was a stock 360 with headers, I put one on there and it ran great.

[fomocoguy]

500 cfm is the maximum wide open throttle flow rate; that being said a stock two barrel intake probably won't efficiently move that kind of air flow. Now, if you had a four barrel intake, spacer, and one of these on top it would probably have maximum flow. Either way it will flow better than a stock setup and they are great little carbs!

[Dragon]

Yeah but they consume more fuel when you are just cruising as the barrels are so large they let the vacuum drop low. I got 12 mpg with a remanufactured factory installed 350 CFM 390/360's 2V 2100 Autolite. I got 8 with a Holley 500 new that was properly jetted for this altitude. A 600 4V Holley gets better mileage and pulls better and smoother power. If you open a 500 all the way at an idle airflow will drop to nothing and the engine will crawl its way up to about 1200 rpm. If you do that with the 600 or the 2V 350 the truck will just roll away and keep gaining speed.

Try this to see if your 360 needs a 500cfm all at once or a little less or a little more.
Courtesy of Pony Carbs. http://www.ponycarburetors.com

http://www.ponycarburetors.com/default. ... ulatingcfm

Use no more than 80% VE for the street without good heads and manifold or a better cam.

A 360 is then is rated for 416 CFM at 5000 RPM and a 360 will not be revving that high without a cam and springs and be efficient.

So at the stock 4400 rpm factory redline. You get 366 cfm at .8 VE. With a cam you could get .85 VE for a 389 CFM. Well the Factory put a 350 CFM carb on them .

This bodes well for a 600 Holley as the primaries are 300 cfm and if you need more a stock out of the box 600 will feed just what more your engine needs.

[3rdowner]

I have the chrome 500 cfm holley 2 barrel. The truck use to be cold blooded and would stall if it were cold and you took off from a stop sign. I changed to the holley and all that stopped, but I think my gas mileage went down. 12 miles to the gallon maybe with 352 auto and 410 to 1 dana 60

ED

[Dragon]

That meant the other carb needed replaced or rebuilt.

The rules for that is
Replace a carb when the throttle shafts and choke shaft get sloppy. Rebuild as long as the shafts are tight.

[fitzwell]

had a 500 2bbl on my old ranchero. Ran like stink

If you have the $$ a 390 holley is the hot setup. Takes a while to tune one, but once it's right, they rock. Added benefit....Killer fuel economy.

[hotrod ford]

i think that 390 holley is a 4 bb. probably for smaller engines. i'm talking about somthing for a 2bb intake.

[Dragon]

The Holley 390 is a 4V there is a 350 2V along with the 500.

[hotrod ford]

500 cfm is the maximum wide open throttle flow rate; that being said a stock two barrel intake probably won't efficiently move that kind of air flow. Now, if you had a four barrel intake, spacer, and one of these on top it would probably have maximum flow. Either way it will flow better than a stock setup and they are great little carbs!

so you could add a 2 bb to a 4bb intake?

[hotrod ford]

i'm asking all of this because i'm 99.9% that i'm gonna get a stock 71 swb while i'm on leave. i've ran the #s and from what i've seen in pics and looked at on 71 codes it is all original. it has a 360 2bbl with a c6 and 3:00 rear. i want to keep the stock look but still have some fun at the same time.

[papabug71]

i'm asking all of this because i'm 99.9% that i'm gonna get a stock 71 swb while i'm on leave. i've ran the #s and from what i've seen in pics and looked at on 71 codes it is all original. it has a 360 2bbl with a c6 and 3:00 rear. i want to keep the stock look but still have some fun at the same time.

The 3:00 gears are what will hurt your "fun" level. They are kinda doggy. If nothing is wrong with the autolite thats on the truck, I would leave it & save for cam, springs, carb, intake & exhaust. After that, do the gears & make it a screamer. All while keeping the stock apperance!

I hope you get it. I would love to have a short/wide bump.

[hotrod ford]

i'm asking all of this because i'm 99.9% that i'm gonna get a stock 71 swb while i'm on leave. i've ran the #s and from what i've seen in pics and looked at on 71 codes it is all original. it has a 360 2bbl with a c6 and 3:00 rear. i want to keep the stock look but still have some fun at the same time.

The 3:00 gears are what will hurt your "fun" level. They are kinda doggy. If nothing is wrong with the autolite thats on the truck, I would leave it & save for cam, springs, carb, intake & exhaust. After that, do the gears & make it a screamer. All while keeping the stock apperance!

I hope you get it. I would love to have a short/wide bump.

thats the great thing, i already have a 9" still in my garage with 3.73 gears. oh, it does have headers on it already, but thats it. i have been looking at a cam kit edelbrock has for a 360.

[Dragon]

They are rated differently than a 4 barrel. I think I heard the estimate is 2 barrel rating x .78 = comparable 4 barrel. That would make it about a 390 carb.

Code: Select all

From Holley Tech support yes 2Vs are rated different.

Subject: RE: Carb flow

4BBL = 19" & 1.5" Hg. MV

2BBL = 19" & 3.0" Hg. MV

"Hg. Divided by .07355 = " water

1.5 divided by .07355 = 20.394289 " water 3.0 divided by .07355 = 40.788579 " water
]

The 2V has twice the flow through it making it not as big by half as a similar sized 4V. So the 500 Holley 2V would have to have 2 barrels(not throttle plates) twice the size of all 4 barrel to equal 500 cfm.

That points back to slower flow through the barrels. Slower flow means less vacuum.

Mercury (Hg) columns are used to measure vacuum and pressure. As the mercury does not flow easily and get sucked out or blown out of the column like water would, then they convert down to water for the equivalent flow rate in CFM.

[willowbilly3]

I have the Holley 350 cfm on my stock 390 with 4 speed and 3.73 axle. It is fine at low to mid rpms but does fade aout just past mid range. Milage was the same as the stock carb but it now starts much easier and doesn't do the heat soak fuel perc thing anymore.
The carb is really finnicky about fuel though. I have ran 10% alky with no problem before but now if I try it, it gives me fits. Even certain brands of regular make it idle poorly.