750 double pumper
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Freshman User
Joined: Apr 2005
Posts: 27
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From: Michigan
750 double pumper
Is a 750 double pumper too big for a almost stock 460. right now i have a 600 vacuum secondarie holley and i just don't think i'm getting all i could. only reason i'm asking is that i have someone offering me the carb at a price i can't pass up, i guess i could always jet it down but i'm not going to claim to be the best person with carbs
Elder User
Joined: Apr 2007
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From: Los Alamos
On a mostly stock 460 a 750 d/p will work fine..Take some time, read some articles and get it tuned, it will be a good road carb. I used to have a book that covered the tuning, tweaks and mods that was easy to follow, and very comprehensive..not sure what happened to it..have not seen it around in years..but if I can remember who wrote it, I'll let you know. It's worth having.
Off road, however, the double pumpers are a handicap..Even if you put the whistle vents in the bowls, they don't like steep climbs much. If you do a lot of climbing around the steep hills, it is not a great choice.
Off road, however, the double pumpers are a handicap..Even if you put the whistle vents in the bowls, they don't like steep climbs much. If you do a lot of climbing around the steep hills, it is not a great choice.
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Freshman User
Joined: Apr 2005
Posts: 27
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From: Michigan
Thanks for the advice both. truck is pretty much a pavement stomper, i take it off road every now and then but its usualy on flat terrain for the most part. i already have a free flowing flowmaster exaust and plan on putting a little bit bigger cam and an intake on once my overtime picks back up. not an everyday driver, i have an 03 i drive to and from work. 60 miles a day with that 460 would kill my wallet in a heartbeat.
Post Fiend
Joined: Mar 2004
Posts: 6,056
Likes: 8
From: Union, Washington
D/P carbs are race carbs and have no place on a street engine except possibly on a light street car. It will give poor mileage and probably worse preformance than a vacuum secondary unit. Damn, read what Holley has to say. Look at the 10th question down.
Holley Performance Products Frequently Asked Questions
Holley Performance Products Frequently Asked Questions
Elder User
Joined: Feb 2002
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From: Portage Twp, PA
I think you're going to find that a 750 CFM carb is going to be a little too much on a stock 460, ESPECIALLY a double-pumper. It's going to depend on your cam and compression, really.
Double-pumpers aren't the best selection for a heavy vehicle, or one with an automatic transmission, unless it's got a high-stall converter. As far as CFM goes, you need to be getting a lot of air into and out of the engine for the bigger carb to work well. The venturis on the 750 are too big, and you'll suffer from poor low-end performance (smaller venturis = better throttle response).
Just as an example, several years ago I had a stock '74 truck 460 (only mod was Flowmasters) in a '78 LTD II. I pulled the 600 CFM Motorcraft 4V carb off and replaced it with a Holley 750 CFM vacuum-secondary. Even after it was tuned, I was still 4/10ths slower at the dragstrip than I was with the POS Motorcraft.
HTH,
Pat
Double-pumpers aren't the best selection for a heavy vehicle, or one with an automatic transmission, unless it's got a high-stall converter. As far as CFM goes, you need to be getting a lot of air into and out of the engine for the bigger carb to work well. The venturis on the 750 are too big, and you'll suffer from poor low-end performance (smaller venturis = better throttle response).
Just as an example, several years ago I had a stock '74 truck 460 (only mod was Flowmasters) in a '78 LTD II. I pulled the 600 CFM Motorcraft 4V carb off and replaced it with a Holley 750 CFM vacuum-secondary. Even after it was tuned, I was still 4/10ths slower at the dragstrip than I was with the POS Motorcraft.
HTH,
Pat
Senior User
Joined: Mar 2008
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the 750 dp will be to big until you jet it down, or motor mods (headers, cam, intake)
it will foul plugs and build up carbon on the valves and top of pistons causin poor performance
bear 45/70 was that a joke, ive always ran dp's on the street
it will foul plugs and build up carbon on the valves and top of pistons causin poor performance
bear 45/70 was that a joke, ive always ran dp's on the street
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Post Fiend
Joined: Mar 2004
Posts: 6,056
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From: Union, Washington
When did changing jets alter the CFM rating? If you always run D/Ps on the street shows you know nothing about carburation and should never advise anyone about carb issues. My God, read what Holley says before you make foolish statements.
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Freshman User
Joined: Apr 2005
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From: Michigan
well i didn't mean to get everyone into a big argument, i was just wondering if it would work, holley does offer a 4150hp that is streetable with the ford kickdown, but either way i have a manual valve body in my trans anyways so thats not even the issue.
as far as my truck being to heavy for the carb, a good freind of mine that off roads ran the same carb on his 77 250 on a 2 1/2 ton millitary chassis with combine tires and he said it outperformed a 750 single pump. motor was basicly stock with an intake and a little bit bigger cam like i plan on running.
but like i said, i am very limited on knowlage about carbs.
as far as my truck being to heavy for the carb, a good freind of mine that off roads ran the same carb on his 77 250 on a 2 1/2 ton millitary chassis with combine tires and he said it outperformed a 750 single pump. motor was basicly stock with an intake and a little bit bigger cam like i plan on running.
but like i said, i am very limited on knowlage about carbs.
Elder User
Joined: Apr 2007
Posts: 617
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From: Los Alamos
You didn't start a fight..opinions vary, thats all.. Bear is a smart man, and he has been around the block more than once playing with stuff. But like all of us, he has formed his opinions based on his experiences.. I have had perfectly good luck with d/p Holleys, but as I said earlier, and perhaps should have elaborated more on, they can be made to work if thats what you have, but they have GOT to be tuned properly for a specific application, and that takes time, skill, testing, and learning as you go.. My first few go's at them were colossal failures..but I learned, tweaked, and got them dialed in and they performed admirable....If your carb experience is "very" limited, there are several better choices for what you want..
My personal favorite to make a 460 stand up and dance is a quadrajet..fairly easy to set up and to tune, and they love the 460..but they cost to buy, adapt, and set up.
If you have the cash, check out the Jet Performance Streetmaster big block.. It's for a 396+ chevy motor, but your 460 will love it....
My personal favorite to make a 460 stand up and dance is a quadrajet..fairly easy to set up and to tune, and they love the 460..but they cost to buy, adapt, and set up.
If you have the cash, check out the Jet Performance Streetmaster big block.. It's for a 396+ chevy motor, but your 460 will love it....
Post Fiend
Joined: Mar 2004
Posts: 6,056
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From: Union, Washington
Something isn't right a 750 should never out mpg a 600.
Senior User
Joined: Mar 2008
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bear, didnt mean to start a pi%$#@ match,
ive had a 68 firebird 400 with 502 hp at the wheels with a tuned 750 dp
79 stang with 351 478 hp at the wheels
and now a 460 with 500+ hp and 600+ torq also a dp
why is a dp not good for the street, i didnt see holley state why
like i said, not trying to start a feud but why not for street!!!!!
New User
Joined: Apr 2008
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I have a stock rebuilt 460 in my 78 Mud Truck and im running a 780 Dual Feed single pump and its worked awesome for years. Im not sure as far as the double pumper goes but just talkin about CFM that 780 has been great!
Post Fiend
Joined: Mar 2004
Posts: 6,056
Likes: 8
From: Union, Washington
bear, didnt mean to start a pi%$#@ match,
ive had a 68 firebird 400 with 502 hp at the wheels with a tuned 750 dp
79 stang with 351 478 hp at the wheels
and now a 460 with 500+ hp and 600+ torq also a dp
why is a dp not good for the street, i didnt see holley state why
like i said, not trying to start a feud but why not for street!!!!!
ive had a 68 firebird 400 with 502 hp at the wheels with a tuned 750 dp
79 stang with 351 478 hp at the wheels
and now a 460 with 500+ hp and 600+ torq also a dp
why is a dp not good for the street, i didnt see holley state why
like i said, not trying to start a feud but why not for street!!!!!