Moparts
how do you use your DP holley?
talking with a buddy and
over how you would drive with a manual 2ndary double pumper.
i said its not like a afb/avs vac 2ndary carb,it feathers the transition on the back opening up.
and with a DP,you dont mash it all the way till rpms come up and then stab the rest.
I also say it works better on a stick car with the manual DP
opinions and your way of driveing/luanching/
Posted By: topside
Re: how do you use your DP holley? - 08/02/11 05:36 PM
Vacuum draws fuel based on engine demand, DP dumps fuel based on throttle position. Both cover the "hole" when secondaries are opened. Vacuum is arguably better for partial secondary openings where you don't want to draw too much fuel. DP seems easier to tune for applications where secs are whacked open, as in drag racing.
On my footbrake 6000-stall drag car, it's staged about 1600-2000, then hammered; RPM comes up immediately & cleanly if I'm right for the conditions.
For my street cars, which I drive more conservatively, the vac secs on those allow better MPG; since they're not geared and/or don't have a lot of stall, the motor gets what it needs for a smooth transition. On street 4-speed cars, though, I've run DPs when the usage is more aggressive or they have 3.73s or better. Like a lot of things, it depends on the combination & application.
Theoretically, you should be able to tune either style carb for the same response, but some are easier than others and sometimes ya gotta work with what you already have.
Posted By: ademon
Re: how do you use your DP holley? - 08/02/11 05:39 PM
I like DP's.
(640x480).jpg "6759325-71Demon340(63)(640x480).jpg")
Posted By: Ledman_70
Re: how do you use your DP holley? - 08/11/11 01:44 PM
Last year I pulled the 750 SP off my 426 wedge and installed an 800 DP...felt like it added 40 hp to the car! when I stab it now it pulls a HELL of a lot harder than it ever did with the 750 vaccum.
Posted By: Rug_Trucker
Re: how do you use your DP holley? - 08/11/11 02:20 PM
I have a 650 spreadbore that is a great door stop.
Posted By: Mr.Yuck
Re: how do you use your DP holley? - 08/11/11 02:32 PM
huh? just like any other carb. If it smells gassey or uses twice as much gas you didn't set it up right.
as far as launching just come up on the converter and fine the right spot for WOT. Same with clutch see what your car likes and try and hit that spot each time.
Posted By: YO7_A66
Re: how do you use your DP holley? - 08/11/11 03:33 PM
In cooler weather, I can be at a stop and then go from idle to full throttle with no problem. In warmer weather at a stop, I bring up the rpms (mid teens) and then let go of the brake and go to full throttle at the same time.
I am currently using my wideband to retune my secondaries to limit the fuel on the secondary pump so that I do not need to use my brake from a stop to go to WOT in warmer weather. I am finding out that my combo does not need the full 30cc's from the secondary pump even when using the smallest volume pump cam. I am adding an air gap between the secondary pump arm and the cam and that is keeping my cruise to WOT A/F ratio where it needs to be. I am still working on this to lean out the idle to WOT though. I can still mash it at idle in warmer temps without a bog, but it is not as crisp,,, yet.
Posted By: StealthWedge67
Re: how do you use your DP holley? - 08/11/11 04:42 PM
You should be able to just flat mash it. If it coughs or bogs, then either the carb isn't set up properly, or (more likely) the application is not suitable for a DP, and a VS carb would work better.
Posted By: 70Cuda383
Re: how do you use your DP holley? - 08/11/11 04:54 PM
I had the 750HP which is a DP without a choke, on my 438 stroker, 5-spd manual truck.
I had some issues with having to feather/pump the gas to get the motor off idle without stalling, but once the RPM was up, and the clutch pedal was out, I could stab it WOT and it would go. no bogs, no hesitations, no transitions etc.
I played with the pump cam on the primaries, and was able to get the "just off idle" hesitation out of it, so that from a dead stop, I could simply give it a little gas, let the clutch out, then stomp it WOT.
with that 750HP, my 4200 lb truck, 438 cu inches, 4.56 gears...I was able to get about 12 MPG on the highway, and around 9MPG in town.
Posted By: ZIPPY
Re: how do you use your DP holley? - 08/11/11 05:25 PM
I stomp the throttle to WOT off idle.
Big accelerator pumps, lots of initial timing, correct carb selection and so on are needed
to make that possible. High stall converter is helpful.
Quote:
You should be able to just flat mash it. If it coughs or bogs, then either the carb isn't set up properly, or (more likely) the application is not suitable for a DP, and a VS carb would work better.
If you can't hit WOT off idle, there has been a mistake made somewhere.
Posted By: BSB67
Re: how do you use your DP holley? - 08/12/11 02:57 AM
Quote:
I stomp the throttle to WOT off idle.
Big accelerator pumps, lots of initial timing, correct carb selection and so on are needed
to make that possible. High stall converter is helpful.
Quote:
You should be able to just flat mash it. If it coughs or bogs, then either the carb isn't set up properly, or (more likely) the application is not suitable for a DP, and a VS carb would work better.
If you can't hit WOT off idle, there has been a mistake made somewhere.
Mash it at any speed, and rpm, and it should run fine if it is set up right
Posted By: ph23vo
Re: how do you use your DP holley? - 08/12/11 04:15 AM
i had a 750 DP on my 340 car stock converter, 4:57 gears..stock 340 with solid 530 cam and LD 340 intake, stock manifolds, street tires.. the DP would kill the torque surge on launch allowing the car to run hard on street tires/street trim..12:80,s @ 108 mph.. dan
Posted By: goldmember
Re: how do you use your DP holley? - 08/12/11 06:33 AM
Quote:
talking with a buddy and over how you would drive with a manual 2ndary double pumper.
i said its not like a afb/avs vac 2ndary carb,it feathers the transition on the back opening up.
and with a DP,you dont mash it all the way till rpms come up and then stab the rest.
I also say it works better on a stick car with the manual DP
opinions and your way of driveing/luanching/
HUH??? A DP IS the choice for WOT performance. There is no waiting to put the pedal down,unless tire spin is an issue.
Posted By: POS Dakota
Re: how do you use your DP holley? - 08/12/11 08:57 AM
Quote:
I stomp the throttle to WOT off idle.
Big accelerator pumps, lots of initial timing, correct carb selection and so on are needed
to make that possible. High stall converter is helpful.
Quote:
You should be able to just flat mash it. If it coughs or bogs, then either the carb isn't set up properly, or (more likely) the application is not suitable for a DP, and a VS carb would work better.
If you can't hit WOT off idle, there has been a mistake made somewhere.
Exactly!!!!!!
My annular booster 750 absolutely freaking rocks off idle.
I threw it on a friend's car and he didnt want to give it back. 
If it doesnt work that way, you have an issue with the tune.
At least on a more "conservative" cammed streeter. I can see it becoming a little difficult with a huge cam at idle with low vac...but then again maybe not!
Posted By: abodyjoe
Re: how do you use your DP holley? - 08/12/11 12:35 PM
Quote:
talking with a buddy and over how you would drive with a manual 2ndary double pumper.
i said its not like a afb/avs vac 2ndary carb,it feathers the transition on the back opening up.
and with a DP,you dont mash it all the way till rpms come up and then stab the rest.
I also say it works better on a stick car with the manual DP
opinions and your way of driveing/luanching/
not really 100% sure what your asking.
i was running a proform 750DP on my 360/904 street car. i drove it like a regular car. it was great. cruised at low speeds great and when ever i want it to go i just put the pedal to the floor boards and the car just got up and went.. my car ran like an injected car.
if you have to feather the throttle then something isn't set up right.
Posted By: 69Chrgr
Re: how do you use your DP holley? - 08/12/11 12:50 PM
Double pumper, vacumm secondary, either carb with the right tuning/modifications can give you the ability to flat punch the car and have it perform. the double pumper will be easier to tune, but if you go to an nhra race, and go look at the super stock and stockers, you will see cars that will run all the way in the 9's with vaccumm secondary cars, holleys, afb's, quadrejets, thermoquads, and more. They all run well if you set the carb up correct. also a big factor is the motor needs to be set up right and matched with the right converter. sometimes the wrong cam, headers, intake, headers etc will have a guy work on a carb over and over trying to fix a problem. but sometime trying to fix a carb problem is like trying to fix a symptom, not the disease
Duane
Duane
Quote:
Quote:
talking with a buddy and over how you would drive with a manual 2ndary double pumper.
i said its not like a afb/avs vac 2ndary carb,it feathers the transition on the back opening up.
and with a DP,you dont mash it all the way till rpms come up and then stab the rest.
I also say it works better on a stick car with the manual DP
opinions and your way of driveing/luanching/
not really 100% sure what your asking.
i was running a proform 750DP on my 360/904 street car. i drove it like a regular car. it was great. cruised at low speeds great and when ever i want it to go i just put the pedal to the floor boards and the car just got up and went.. my car ran like an injected car.
if you have to feather the throttle then something isn't set up right.
ok,so if its set up correct both can be stomp from off idle to wot and have no bog/stumble/flat spot.
when I had my 4 speed in the A-body,with the manual DP,i would have to have rpm up over 2000 rpm before I could stab it WOT.
some times i would launch 1/2 throttle and when the rpm started to level off stab it WOT.
when i was showboating and spinning the tires in the dirt or around a corner on pavment,i would side step the clutch in 1st gear and keep the rpms up with the tires broke loose...but i would have to "pump" the throttle to keep it right at the redline then snag 2nd.
now the vac 2ndary carb I would just stab it,hold it to the floor and it did its thing and never had to pump/feather the gas to keep rpms under control, when it redline it was just shift it.
it was said you have to learn how to drive with a manual DP,that what I am asking...how do you do it?
I have saw in car vids of road race car with 4-speeds,they seem to stab it and it is pulling but then you see them pumping the 2ndarys(I think?) to get it up in the rpms faster.
like its to much in that gear and they just pump it a few times holding it longer each time as the rpm goes up to feather it till it takes all the carb and is screaming WOT then shift.
my thought is a DP is more for an 4-speed and a vac 2ndary carb is more for an auto car??
Posted By: 340SHORTY
Re: how do you use your DP holley? - 08/12/11 02:32 PM
boat anchor
Posted By: YO7_A66
Re: how do you use your DP holley? - 08/12/11 02:58 PM
If you can watch the affects of a DP carb with a wideband sensor, you will notice that at a steady cruise and then go to WOT, you can see the richening affect of the twin pumps. The A/F meter will go rich immediately at WOT. This can be leaned out with the secondary cam and secondary arm adjustment (I have found that the squirter does not change the A/F much at WOT). But if you are rich at cruise to WOT then you are going to be allot richer from idle to WOT in an auto car. I believe that the trick is to adjust the secondaries on a DP to only give the engine wants and no more. Smaller engines like mine do not need the full 30cc's that a standard secondary pump provides, so limiting that volume is the key for mine. As others have said, it is in the tuning.
Since I have my WOT A/F ratio tuned to 12.8, I am now tuning the A/F ratio from a cruise to WOT and I almost have it. I am currently showing the cruise to WOT spike in the 12.5 range and I hope to lean it out to about 12.8. I have been as rich as 10.8 and changing the secondary cam and secondary cam to arm gap has allowed me to lean it out. The response after leaning out this rich spike is definately crisper now, even at lower rpms.
Next I will test my idle (foot on the brake) to WOT and see how that is affected.
I do know for a fact that too much fuel at any speed/rpm to WOT will kill the performance/response with a DP.
I am a believer that a DP is very tunable for a street driven car.
Posted By: 383man
Re: how do you use your DP holley? - 08/12/11 05:23 PM
Quote:
Quote:
Quote:
talking with a buddy and over how you would drive with a manual 2ndary double pumper.
i said its not like a afb/avs vac 2ndary carb,it feathers the transition on the back opening up.
and with a DP,you dont mash it all the way till rpms come up and then stab the rest.
I also say it works better on a stick car with the manual DP
opinions and your way of driveing/luanching/
not really 100% sure what your asking.
i was running a proform 750DP on my 360/904 street car. i drove it like a regular car. it was great. cruised at low speeds great and when ever i want it to go i just put the pedal to the floor boards and the car just got up and went.. my car ran like an injected car.
if you have to feather the throttle then something isn't set up right.
ok,so if its set up correct both can be stomp from off idle to wot and have no bog/stumble/flat spot.
when I had my 4 speed in the A-body,with the manual DP,i would have to have rpm up over 2000 rpm before I could stab it WOT.
some times i would launch 1/2 throttle and when the rpm started to level off stab it WOT.
when i was showboating and spinning the tires in the dirt or around a corner on pavment,i would side step the clutch in 1st gear and keep the rpms up with the tires broke loose...but i would have to "pump" the throttle to keep it right at the redline then snag 2nd.
now the vac 2ndary carb I would just stab it,hold it to the floor and it did its thing and never had to pump/feather the gas to keep rpms under control, when it redline it was just shift it.
it was said you have to learn how to drive with a manual DP,that what I am asking...how do you do it?
I have saw in car vids of road race car with 4-speeds,they seem to stab it and it is pulling but then you see them pumping the 2ndarys(I think?) to get it up in the rpms faster.
like its to much in that gear and they just pump it a few times holding it longer each time as the rpm goes up to feather it till it takes all the carb and is screaming WOT then shift.
my thought is a DP is more for an 4-speed and a vac 2ndary carb is more for an auto car??
If the DP stumbled on the gas anytime then it is not tuned or set-up right. Just because the vac carb ran good and the DP did not does not mean you are driving it wrong or the DP is the wrong carb. It just means the DP is not tuned to the combo. Vac carbs are more forgiving and can cover up lean spots in the secondary system as it opens. Thats becausae when you slam the throttle to the floor with a vac carb the secondary's dont open until the eng load and the venturi vac let it open. Course on a DP when you slam it to the floor the secondary's go wide open and if you dont have the secondary pump shot right or the secondary's are to lean then it might stumble. You have to have the mixture right for the DP to work good as you are going from closed throttle on the secondary's to wide open in less then a second and if the mixture (pump shot , jets , air bleeds) is not correct it can stumble for sure.
Thats why vac carbs are recomended for auto because if you dont have the DP mech linkage carb set right then you have to tune it to be right. With stick cars you can get the rpm's up before dumping the clutch and can cover up a flat spot easier then an auto car will. But the vac carb is so forgiving as when you slam it it only opens the primary side so you dont have all that extra air coming right in that needs the mixture tuned right as the secondary will open slowly by the venturi vac and does not get a fast blast of alot of air. It smoothly comes in nice and easy and it opens slow enough that you dont need a pump on the secondary's since it opens slow enough that there is no stumble since it does not blast open and go lean. Ron
Posted By: dOoC
Re: how do you use your DP holley? - 08/12/11 05:40 PM
Quote:
HUH??? A DP IS the choice for WOT BBQ-ing.
FIXED ... 
Posted By: Anonymous
Re: how do you use your DP holley? - 08/12/11 05:42 PM
Quote:
Quote:
HUH??? A DP IS the choice for WOT BBQ-ing.
FIXED ...
Posted By: dOoC
Re: how do you use your DP holley? - 08/12/11 05:46 PM
gy ... Are THESE the naughty and uNcorrect pics you have been down-loading ?
Posted By: feets
Re: how do you use your DP holley? - 08/12/11 06:07 PM
Here's how I use a Holley DP:
Posted By: Anonymous
Re: how do you use your DP holley? - 08/12/11 07:06 PM
Quote:
Here's how I use a Holley DP:
Ironic that the door stop has "big foot" moulded into it...
Posted By: feets
Re: how do you use your DP holley? - 08/12/11 08:03 PM
Quote:
Quote:
Here's how I use a Holley DP:
Ironic that the door stop has "big foot" moulded into it...
