780 Holley Double Pumper Carb for the Street??

This Carb was originally a 650 Holley DP.For years and years of tuning I got nothing but instant fouled carbon spark plugs.I must have gone through 100 sets.I finally went to a local speed shop and the owner told me that the Carb was to small for my Chevy 402 BB.So I gave it to him and he sent it to a company in Texas.They made it flow 780cfm's and put in a 4 corner idling circuit.Finally after all those years of looking at carbon fouled plugs it fixed that problem.The problem now is with Idling.Its a very touchy carb and if I set the Carb to Idle at 1000Rpm's as the engine gets hotter the Idling Rpm's starts to climb to around 1500RPM'S.I have heard that the Double Pumper Holley is not all that good for the street.I do have a healthy sized Cam in it.I have a 4 speed Muncie also.Duration At .050 is 248 and 248,595 lift on intake and exhaust.I am only going to be driving this car on the street and Im wondering if these Holley Double Pumper Carb's suck on the street??:cool:

I ran a 750 DP on my '68 GTO - (400 cid) with a very similar cam. No problem once I had it tuned.

I always had to set my idle with the engine at full operating temp, then baby it quite a bit when it was cold. Used a manual choke. What kind of choke to you have, if any?

Yeah, it was too much cam and the wrong gearset (4.10) for the street. It was tempermental, took a lot of tuning, had too much compression for pump gas, and got horrible mileage. The MT wrinklewalls I ran werenn't quite right for the street either. However, I didn't build it as a cruiser, drive it 200 miles to a car show, or putz up and down Dodge Street on Saturday night. I built it to be a crazy-ass, take-a-deep-breath-when-you-punch-it, whadda-you-lookin-at-buddy, over-the-top, holy-cow-what's-he-got-in-that-thing, stoplight bandit. That's what one part of the hot rod world was - and still is.

Jack
My motto back in the day was: "Too much is just about right."

Most DP carbs run a progessive linkage and only run two barrells until you stick your foot into it. I've always ran DP and never had a problem on the street.

later

dennis

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Originally Posted by Henry Rifle

I ran a 750 DP on my '68 GTO - (400 cid) with a very similar cam. No problem once I had it tuned.

I always had to set my idle with the engine at full operating temp, then baby it quite a bit when it was cold. Used a manual choke. What kind of choke to you have, if any?

Yeah, it was too much cam and the wrong gearset (4.10) for the street. It was tempermental, took a lot of tuning, had too much compression for pump gas, and got horrible mileage. The MT wrinklewalls I ran werenn't quite right for the street either. However, I didn't build it as a cruiser, drive it 200 miles to a car show, or putz up and down Dodge Street on Saturday night. I built it to be a crazy-ass, take-a-deep-breath-when-you-punch-it, whadda-you-lookin-at-buddy, over-the-top, holy-cow-what's-he-got-in-that-thing, stoplight bandit. That's what one part of the hot rod world was - and still is.

Jack
My motto back in the day was: "Too much is just about right."

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I don't have a choke on mine.Looking back now I should have stuck with a Cam that would work nice with a 3:73 Gear.Maybe a set of Aluminum heads would make up for a smaller Cam and the lower 3:73 Gears??I remember having a 500 lift Wolverine
Cam in the same engine and that idled great with 2:73 or 3:08 Gears and the car was very responsive with my Edelbrock Performer Manifold.It would have been alot better if I had the 3:73's.I would like the car to have power to get in the low 12's or high 11's even though its primarily a Street car.

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.

.....I used to run a Holley 750 double pumper on my 413 small block although I had a MUCH smaller cam. 222/232. This motor is being rebuilt now & the carb is being rebuilt at The Carb Shop in Ontario, CA. It sat for years so I'm having them rebuild it. It used to work great on the street except for it 'stumbled' {hesitated} coming out of the hole. The place is addressing this. But it idled just fine before..... Bill
Oh, I'm using a bigger cam this time, either 230/230 or 236/236.....

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Originally Posted by dennis kelley

Most DP carbs run a progessive linkage and only run two barrells until you stick your foot into it. I've always ran DP and never had a problem on the street.

later

dennis

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I was wondering if you were running a big Cam with the Double Pumper Carb??

I should have got opinion's before putting a 248/248 Cam in my 402 BB.I just thought the bigger the Cam the faster the car would be.(inexpierence i guess)

well the bigger the cam the faster the car is true.... as long as you build the rest of the engine with the cam specs..... i undercammed my first few high performance builds just because i was afraid of over camming

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Originally Posted by thesals

well the bigger the cam the faster the car is true.... as long as you build the rest of the engine with the cam specs..... i undercammed my first few high performance builds just because i was afraid of over camming

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Even though I have stock ported oval port head's the car makes good power from 2500 to 6000 RPM'S.I think though that this Cam could be killing my gas mileage and today that's somewhat important.I never had a working gas gauge in it to see how bad gas mileage was with my 402 BB.Its not fun getting less then 10MPG if the car is only driven on the street!! I know a smaller Cam would give it even better street manners and I could get rid of the 4:11 Race Gear's especially since I don't have an overdrive for it.

my reccomendation would be same thing i did..... forget about gas mileage at all on your classic, you're never gonna get good mileage.... make it your fun car.. drive it maybe 2 times a week just to cruise or go out with a lady or such... and for the rest of the week buy a little beater thats dependable, and gets good gas mileage.... i myself bought an 89 nissan sentra.... its not pretty, and it only has 90 horsepower, but after tuning it the best i could.... i get 42 MPG

69....

I have run a 750 double pumper on a 70 Z/28 with fine results just as the other guys here are saying.

Question: how can some outfit turn a 650 double pumper into a 780 double pumper? I'll tell you how: they piled up a bunch of used parts that included the body of a 780 vacuum secondary carb. They added the bowls from your 650 DP, etc. The carb is probably a mismash of parts....did they know what they were doing? If the carb doesnt run right, then the answer is _______
(insert answer here).

mike in tucson

Well I don't no exactly what all they did to the(650DP to flow 780) Carb other then put a 4 corner Idling Circuit, because it was many years ago.I have tried 2 Holley Double Pumper Carb's but regardless of the tune my spark plugs alway's were carbon fouled.I had new MSD Ignition,Coil,Plugs,Advanced Timing at Idle.The one thing it did was run great with Nitrous the first time I used the NOS System.After that I had the carb sent out to Texas to cure the fouling of the plugs.Now with the Nitrous I get instant detonation luckily my engine parts are Forged.

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Originally Posted by thesals

my reccomendation would be same thing i did..... forget about gas mileage at all on your classic, you're never gonna get good mileage.... make it your fun car.. drive it maybe 2 times a week just to cruise or go out with a lady or such... and for the rest of the week buy a little beater thats dependable, and gets good gas mileage.... i myself bought an 89 nissan sentra.... its not pretty, and it only has 90 horsepower, but after tuning it the best i could.... i get 42 MPG

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I never really worried about gas mileage until these 2 last years.Only because this is not meant to be a race car.I would like to think I could get at least 10mpg with a 402 BB but with the rather large Cam I have who knows:confused:

The one thing I don't have is a choke on the carb.I wouldn't think that would matter on a 90 degree day though.Im afraid to take it out on the road until I can get it Tuned and Idling correctly.I could live with the big Cam even though it has a Lopey Idle.Just need to find the right Carb.

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

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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. :)

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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.

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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. :)

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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.

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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.

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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....

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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.

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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 .

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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

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

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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....

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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:whacked:

[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]

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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.

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i really do not think my car is that bad at idle:LOL: 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

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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.

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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....:D

just put fuel in my car 5.00 a gallon so it is a very short fun trip . but i can not drive it much any ways. but i still like to look at it just setting there.just like young goood looking women.

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just like young goood looking women.

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And just how young are we talking, hhmmmm??? :eek: Hhaa!

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Originally Posted by 1JohnnyO

And just how young are we talking, hhmmmm??? :eek: Hhaa!

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:D well not to young. must be old enough to:confused: buy beer??:3dSMILE:

Basically my car has been operated only Idling depending on how long sometimes it takes to Idle.That simply is no fun!!Last time I took it out on the street was when I picked it up from my local shop.It felt alot better power wise(lower rpm power) with the new Torker 2 manifold I put on there in place of the Holley Strip Dominator.Anyway before I took it to the local shop I was backing the car down my driveway and the brakes failed.Well across the street was another home and driveway.I panicked trying to stop the Car and it hit the bumper of a late model chevy car.I did about $750 damage to that car and my back bumper just had some paint scratches.I thought it was that the cam was to big but it was something else. I also did not have a vacuum canister in there to help me with the Braking.I have it in there now.

the big carb can work if tune in but just for a driver the small carb will work better .i have had very good luck with the afbs carter / edlebrocks i see this has how much farting around you want to do with your carb you have on it now at w.o.t this would be a good carb tune in . but if you are driving it and not looking for the max out of your com then small afb would work very good i have done this with a holley on a big block vett it was over carb for the rpm of the engine

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afb would work very good i have done this with a holley on a big block vett it was over carb for the rpm of the engine

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Another reason to stick with a vacuum secondary carb.:D