Thread: 780 Holley Double Pumper Carb for the Street??

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Hot day here in Texas is 105 degrees.So you all ready half way there before you even turn it on.

Originally Posted by DennyW

You wouldn't think a choke would matter on a hot day. How ever, it does. The engine is a combustion engine. That means it's designed to work, and work good When it's up to temperature. Did you know it takes approximately 1 hour of engine run time to heat the block to even temperature ?

The initial start up, and for the first 3-5 minutes require a little richer mixture(needs a little more fuel cold) until there is enough combustion chamber temp to ignite the fuel properly. Just some thoughts.

Thats probably the only thing thats going to help me is a choke.Taking 10 minutes to Idle is ridiculous.I can go out and buy a new Carb but I just will have the carbon fouling of my spark plugs again.Im not an expert tuner but this was the reason for having the 650 DP sent out to get rebuilt.Its a very touchy Carb with the 4 corner Idling circuit and when it does idle, it picks up Rpm's at Idle.It goes to 1000 rpm to 1500rpm's without touching anything.It sounds almost like it start's to run lean.

Originally Posted by DennyW

Yes, the choke will actually be a good thing. The picking up rpm's can mean a couple things. If it's a first start up, it's going lean when the rpm's goes down, and richins up a little when the rpm's goes up. Try that choke for sure. Also, the other is simply if you do not have the 4 adjustments the same turns out, and, or, fine tunned. You need to hook up a vacuum gauge to set them evenly.

I do have the 4 idle air mixture screws.I think this Carb is very touchy but it has run good in the past on the street,never good with the Nitrous though.I never tried hooking up a vacuum gauge to set them evenly.It's a good idea that im going to have to try.Im hoping this weekend I can pull the car out of my garage without dying of carbon monoxide better yet I may just push it out if I can.

Originally Posted by 69muscel

I was also wondering when you said how bad your gas mileage was??How many MPG did you average??Your engine and combination seems very similar to mine.

Somewhere between 4 and 10 . . . depending mostly on my right foot.

1150 holley idles fine at 1000. big cam 275 -287 @.050 drive it on the street runs ok much better at 4500 and up. what you need to do is open the back barrels there is a screw for this and back down the front idle screw you may be past the idle transfer slots on the carb and by cracking the back you will let more air and fuel and use the idle circuit this may help with fuel mix

I still run a 650 dp on a 302 ford and it has a mild cam and AFR 165 heads. The carb works so well on this motor its scary. Dual plane intake to.

later
dennis

Imo double pumpers are for the track, but there are guys out there who know what they're doing and run them on the street with a high degree of success.
As witnessed by a couple of posters above.

That said, I prefer vacuum secondary or air valve secondary carbs on the street.
Makes for a crisp running engine that launches well with mild cam or a fairly big cam.

The dual quad setup I was running on my 2400# 32 roadster utilized straight, non-progressive linkage to the 500 cfm Carters.
The 462" Buick engine responded well with the smaller carbs and tip-in on the secondaries was very smooth.
Kenne-Bell recommended dual 750's, but I elected to go with the 500's because my goal was to have an engine that responded well in the low and mid-range.

If I was building a drag race bracket type car I'd still run vacuum or air valve secondaries.
They are trouble free for the most part and since bracket cars don't need that last little bit of horsepower you can give up some and pay attention to driving the car rather than dinking around with it in the pits.
Kind of a change the oil and go racing car.

I pulled the dual quads and big cam to use in an upcoming project.
An Edelbrock Performer intake and 750 cfm Carter went on the engine along with a milder cam.
The engine responds well and mileage in town runs 10-12 mpg.
Highway runs about 16 mpg.
If . . . you keep your foot out of it.
The carb is jetted/rodded for the 3300' altitude I live at now and it still runs good when we go down the hill to the river at about 450' altitude.

Mileage could be better I suppose, but the 32 has the aerodynamic qualities of a brick.
Fun quotient is pretty high though....

Get yourself a street oriented carb for the car.
I don't have any experience with them . . . yet, but the new Edelbrock AVS carb looks like an excellent way to go for street use.

A quick perusal of jet sizes comparing the AVS to the AFB style has the AVS with slightly leaner jets/rods in comparable carb cfm ratings.
That would help in the mileage dept.


As a small aside, at times I run a mid-sized Holley with vacuum secondaries that is jetted fairly lean.
No gas mileage figures from it, but one strange thing noted was when running sans hood side panels on the 32 in cold weather you could park the car for five minutes and even with a fully warm engine the electric choke would kick on for the startup.
The Carter's electric choke never did that with the side panels off.

Both the Holley and Carter electric chokes operate as they should when the hood side panels are on in cold weather.

Funny stuff, just another one of those hot rod type idiosyncracies we run into with the mix and match of components we are wont to do with these cars....

C9x Imo double pumpers are for the track, but there are guys out there who know what they're doing and run them on the street with a high degree of success.
As witnessed by a couple of posters above.

That said, I prefer vacuum secondary or air valve secondary carbs on the street.
Makes for a crisp running engine that launches well with mild cam or a fairly big cam.

The dual quad setup I was running on my 2400# 32 roadster utilized straight, non-progressive linkage to the 500 cfm Carters.
The 462" Buick engine responded well with the smaller carbs and tip-in on the secondaries was very smooth.
Kenne-Bell recommended dual 750's, but I elected to go with the 500's because my goal was to have an engine that responded well in the low and mid-range.

If I was building a drag race bracket type car I'd still run vacuum or air valve secondaries.
They are trouble free for the most part and since bracket cars don't need that last little bit of horsepower you can give up some and pay attention to driving the car rather than dinking around with it in the pits.
Kind of a change the oil and go racing car.

I pulled the dual quads and big cam to use in an upcoming project.
An Edelbrock Performer intake and 750 cfm Carter went on the engine along with a milder cam.
The engine responds well and mileage in town runs 10-12 mpg.
Highway runs about 16 mpg.
If . . . you keep your foot out of it.
The carb is jetted/rodded for the 3300' altitude I live at now and it still runs good when we go down the hill to the river at about 450' altitude.

Mileage could be better I suppose, but the 32 has the aerodynamic qualities of a brick.
Fun quotient is pretty high though....

Get yourself a street oriented carb for the car.

Amen, I agree completly. I have changed from a mech. secondary to a vacuum carb, several times...maybe 6 or 8, on small blocks and big blocks....and in EVERY case, it was more responsive, and overall, just ran much better. I know guys myself who are running double pumpers on the street, and they seem to run good...but then again, Im not the one riding in the car, or cold starting it. I'll stick with what I know works for me. Im sure you wont be sorry with a good vacuum secondary carb. John

yes the doudle pumper is a bit big 780 for a 402 and a stock type edebrock 750 may work better but the way i see it. is the way it was worded was if a 780 was to big for the street ?and my half ass answer was no .

Originally Posted by pat mccarthy

1150 holley idles fine at 1000. big cam 275 -287 @.050 drive it on the street runs ok much better at 4500 and up. what you need to do is open the back barrels there is a screw for this and back down the front idle screw you may be past the idle transfer slots on the carb and by cracking the back you will let more air and fuel and use the idle circuit this may help with fuel mix

Thats interesting and I will keep that in mind when I attempt to get it running in the next few day's.

Originally Posted by C9x

Imo double pumpers are for the track, but there are guys out there who know what they're doing and run them on the street with a high degree of success.
As witnessed by a couple of posters above.

That said, I prefer vacuum secondary or air valve secondary carbs on the street.
Makes for a crisp running engine that launches well with mild cam or a fairly big cam.

The dual quad setup I was running on my 2400# 32 roadster utilized straight, non-progressive linkage to the 500 cfm Carters.
The 462" Buick engine responded well with the smaller carbs and tip-in on the secondaries was very smooth.
Kenne-Bell recommended dual 750's, but I elected to go with the 500's because my goal was to have an engine that responded well in the low and mid-range.

If I was building a drag race bracket type car I'd still run vacuum or air valve secondaries.
They are trouble free for the most part and since bracket cars don't need that last little bit of horsepower you can give up some and pay attention to driving the car rather than dinking around with it in the pits.
Kind of a change the oil and go racing car.

I pulled the dual quads and big cam to use in an upcoming project.
An Edelbrock Performer intake and 750 cfm Carter went on the engine along with a milder cam.
The engine responds well and mileage in town runs 10-12 mpg.
Highway runs about 16 mpg.
If . . . you keep your foot out of it.
The carb is jetted/rodded for the 3300' altitude I live at now and it still runs good when we go down the hill to the river at about 450' altitude.

Mileage could be better I suppose, but the 32 has the aerodynamic qualities of a brick.
Fun quotient is pretty high though....

Get yourself a street oriented carb for the car.
I don't have any experience with them . . . yet, but the new Edelbrock AVS carb looks like an excellent way to go for street use.

A quick perusal of jet sizes comparing the AVS to the AFB style has the AVS with slightly leaner jets/rods in comparable carb cfm ratings.
That would help in the mileage dept.


As a small aside, at times I run a mid-sized Holley with vacuum secondaries that is jetted fairly lean.
No gas mileage figures from it, but one strange thing noted was when running sans hood side panels on the 32 in cold weather you could park the car for five minutes and even with a fully warm engine the electric choke would kick on for the startup.
The Carter's electric choke never did that with the side panels off.

Both the Holley and Carter electric chokes operate as they should when the hood side panels are on in cold weather.

Funny stuff, just another one of those hot rod type idiosyncracies we run into with the mix and match of components we are wont to do with these cars....

I could try a vacuum secondary but I want to make sure first that with a new choke and some adjustment's first that Im not going to waste my money.I'll keep that in mind though.I think 10-16 MPG for a 462 is ok.I don't know what kind of gears your running.Im running 4:11's with a 28 Inch tire.I may get rid of my Muncie 4 speed and get a good 5 or 6 Speed Trans with an overdrive.Im hoping my car would get at least that good.

there is nothing like the sound of air going thur a 1150 dom

[QUOTE=DennyW]I like vacuum secondaries on the street. 422, 3.91 gears, 28" tires, 780 Holley, 15 mpg. 3900 pound car. Put the 850 on, which is modified, and I get 10 maybe. I just can't keep my foot out of it.

Thats not to bad.Its just that I have owned my car for like 17 years now without a working gas gauge so I had no idea what range in MPG I would get.I underrstand these car's don't get good gas mileage.I could live with 10-15 but when i see other guys posting 5 MPG that puts a hurting on the wallet,especially these days.

[QUOTE=69muscel]

Originally Posted by DennyW

I like vacuum secondaries on the street. 422, 3.91 gears, 28" tires, 780 Holley, 15 mpg. 3900 pound car. Put the 850 on, which is modified, and I get 10 maybe. I just can't keep my foot out of it.

Thats not to bad.Its just that I have owned my car for like 17 years now without a working gas gauge so I had no idea what range in MPG I would get.I underrstand these car's don't get good gas mileage.I could live with 10-15 but when i see other guys posting 5 MPG that puts a hurting on the wallet,especially these days.

i really do not think my car is that bad at idle and that is all i do most of the time is about 2500 to 3000 .but all bets are off at wot and i have never done this in 3 gear

Originally Posted by 69muscel

I could try a vacuum secondary but I want to make sure first that with a new choke and some adjustment's first that Im not going to waste my money.I'll keep that in mind though.I think 10-16 MPG for a 462 is ok.I don't know what kind of gears your running.Im running 4:11's with a 28 Inch tire.I may get rid of my Muncie 4 speed and get a good 5 or 6 Speed Trans with an overdrive.Im hoping my car would get at least that good.

3.70's and a 30 1/2" tall tire.

Runs about 3000 rpm at 70 mph.

With the price of gas about to exceed $3.00 per gallon - in my area (N/W Arizona) a 10% mileage improvement may have the new carb paying for itself.

And maybe I oughta follow my own advice and stick the lean Holley on the roadster and see how it does.

Maybe . . . I drive the car several times a week, so a few - stress few - bucks shouldn't hurt too much.

Fun costs money or how fast do you want to go or something like that....