Hot Rods 390 cfm holley double pumper for street use

I am deciding between 2 Holley 390 cfm carburetors to use on my 265 sbc. 1956 model. It is a single carb intake.

The single pumper has one fuel inlet, manual choke, and vacuum secondaries. It is said to be much more of a street use carb.

The double pumper has no choke and has mechanical secondaries. It also is a lot more adjustable. I live in North Texas which has a moderate to hot climate.

I prefer the mechanical secondaries on the double pumper. And I prefer the appearance. Just wondering if anyone has run the 390 race double pumper on the street. I am currently running 3 Holley deuces. Going to a single four barrel for simplicity and I am tired of the trips look on my car. So thinking simplest may be best.

Any input would be appreciated. Thanks.

 

One thing for sure, you will get a lot of advice on this question.

Since "you like the look" of the dbl pumper, go for it. I think you have already decided.

If the carburetors both have the same throttle body, you could swap out those and have the choke feature. I think. You can also buy parts to convert manual to electric choke if you like.

 

What vehicle?
What will you use it for?
What's your tolerance level?

The single pumper will have better street manners, unless it's in a really light weight car like a T-bucket. Also, I bet the double pumper will be temperamental in winter with no choke.

 

If you already have the 390's, you have really narrowed down your choices. If you don't, you might look at an AFB from a 327 Corvette. Gene.

 

If you can tune the hell out of a Holley either will do what you want, The 390 double pumper is basically a restriction carb for class racing, restrict the carb body bore size but can be modified to run HP. This is an interesting read on dyno testing one.
www.motortrend.com/how-to/holley-390-carburetor-tech-tuning/amp/

You don't say how you're building the 265? Is this a fairly stock engine or are you planning 7K RPM and a lumpy cam.
If it's more of a driver, the AFB recommendation or an edelbrock carb drive very well, crisp low speed throttle response and plenty of secondary capacity. Vacuum secondary holley would do the same.

 

As mentioned, you didn't say how mild or wild the 265 is built. Picking a carb on looks usually leads to some compromises in performance. Having a choke and vaccum secondaries is a pretty proven recipe for a mild 265. But it's your car, so do what makes you happy. Being a bit anal about such things myself, I understand about wanting a look.

 

The single pumper I looked up is dual feed. I couldn't get by on the street without a choke, especially with an automatic trans.

 

Forget this one unless you are a glutton for punishment, it’s a Chineseium knockoff.

 

Im not a fan of the Holley VS for a couple superficial reasons, it just doesn’t look as racy as the double pumper and if it’s working properly you can’t feel the secondaries opening. Having said that I have used a 600 Holley VS on my mild 289 with a c4 and it worked out very well. 289 with cam , intake, carb and headers stock converter and transmission ran 14.0s @ 98 mph in the quarter and get about 17 mpg on the highway.
I think you would be happy with either carb I’d be tempted to try the DP just because.
Good luck

 

Why the 390 cfm? I’ve used the 390 on a 239 Flathead. I think 265 could handle a bigger carb.

 

Ultimately it comes down to your willingness or ability to dial it in. No disrespect intended here. If youre looking for out of the box drop on carb the 390 DP is not it. If you're willing to potentially change power valves, pump nozzles, rejet you're good to go.

Depends on model of 390, I haven't looked them up in some time. It's really meant for wide open throttle class racing with carb as the restrictor, and gets shipped that way. To get off idle and midrange to work smoothly for a driver it needs dialed in.

 

Wow, didn't know they were doing Holley carbs! Is nothing sacred?

That said, I have bought a couple of Chinese carbs for other stuff, one for an ATV, another for a generator, and they are working great.

 

That explains the price. Last Holley I bought was in the $700 range....pre Covid.
Since the OP already has the 390's I'd suggest the vacuum job for simplicity.

 

The vacuum secondary 390 will be more street friendly. But I think there are better choices for your 265 myself, and they're also easier on the wallet. The 390's are a bit more money than the typical 1850 vacuum secondary carbs, and I think even a mild built 265 can handle the 1850 600cfm with vacuum secondaries.

 

I looked at this carb last night. Then i noticed it does not say HOLLEY anywhere on the ad.

 

Yet somehow they get it in there when you search. And first up!

 

I would run the DP, If you want a cheap Holley here ya go !https://www.holley.com/products/fuel_systems/carburetors/factory_refurbished_carburetors/ There are such crazy answers on here it amazes me.

 

Great link.

What's your recommendation ? Jump in

 

I've never found a Holley that needed a choke.

 

I was going to say that until the OP comes back with more information this is pointless.

Then it dawned on me, there is nothing Hot Rod about a single inlet, vac secondary Holley. That's a truck carb.

Make the double pumper work.

 

Forget the race carb. Get a carb/w vacuum secondaries and cfm rating of 500 or less. Take a look at Summit's 500 cfm carb (made by Holley).

 

It's a Shivel-lay!........Stick an Edelbroke on it and drive it!!!
No Kidd 'in a 500 cfm Eddy carb would 'look right' and run wayyyy better than a DP racing carb from Chineee.
As far as "feelin-it" when the secondaries pop in......the air dam on the Eddy had a counterweight on it that allows the secondaries to 'gently' come in as the vacuum increases.
The trick!......drill a hole in the weight to reduces the weight of the counter-weight!
Kind uva trial & error thing. Too light and it will bog when it comes in.
I recommend you sneak up on it.
Trying to drive a double pumper on the street would be a real challenge if you axe me. Too much foot and it bogs pump it on & off and you're dumping raw fuel where it don't need to be.
DP & a stick car on the street............maybe. NOT on an A/T car.
My oppinion
6sally6

 

But it says it is "NEW" and "GOOD"!

 

I have never been a fan of mechanical secondaries on the street.

That said, where I have seen them work best is where the overall CFM of the whole carburetor is right at the appropriate size for the engine, and so long as the transition into the secondary opening is tuned properly.

If one compares the CFM requirements of the typical hot rod engine, versus what is on top for a carburetor, you will likely note that the builder overshot the requirements. In the case of a vacuum secondary carburetor, that's fine, as the secondaries are on-demand. They may rarely, if ever, be opening during normal operation.

With a double-pumping mechanical secondary carburetor, you will have the secondaries open quite a bit.

If you look at a smaller Edelbrock, you will even see that the primaries are quite a bit smaller than the secondaries. They are a minor fraction of the total CFM of the carburetor.

This allows higher venturi velocity, for better, more efficient fuel metering at lower engine speeds (like you have with street driving).

Either way, a 265 (at an optimistic 85% efficiency) at a dangerous 6,000rpm needs only 391.06cfm.

 

I suggest you look up that carb from "Chineee." I hope you like crow. By the way, The Holley 0-80507-1 390 cfm "Nascar" carburetor retails for $825. Still think it's made in "Chinee?"

 

I'm not partial to any particular brand. My wife's cousin's husband has been running a 600 cfm carburetor on his 65 Mustang/w 302 for years without issues.

As Gimpy said, the smaller primaries will be more responsive at lower rpm and return better mpg. If you compared a 2-bbl. carb with a 4-bbl. carb of the same cfm, the 4-bbl. would be more efficient at lower rpm for that reason.

 

It is worth pointing out that a 500cfm 2-barrel and a 500cfm 4-barrel don't flow the same.

They are, for reasons nobody has yet to justify to me, measured with different criteria. Yes, a 4-barrel cannot always be rated using the 2-barrel scale, as it won't hold the vacuum, but you can rate a 2-barrel on the 4-barrel scale. My thinking is that this should just be standardized to avoid confusion.

If I recall correctly, a 2-barrel is rated at 3-inches of Mercury vacuum, and a 4-barrel is at 1-1/2-inches, each wide-open.

That would put a 500cfm 2-barrel at about 355cfm on the 4-barrel scale, give-or-take my brain-math.

 

Two search words I'm unfamiliar with

 

One too many 7-Eleven sandwich's I take it?