Need Advice On Choosing Carburetor , New Build
#1448277
06/05/13 11:37 PM
06/05/13 11:37 PM
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Joined: Dec 2004
Posts: 192 central Florida
titan
OP
member
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OP
member
Joined: Dec 2004
Posts: 192
central Florida
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Getting Towards The End Of My Project, And Am Looking For Advise On What Carburetor Would Be A Good Choice For My Application, Which Is:
451 Low Deck, 10.5 TO 1 comp. Hughes Solid Flat Tappet .543/.563 242/248 @ .050, Stealth Heads,1 7/8 Headers, Street Dominator Intake. 727 W 3200 rpm convertor, 3.55 Gears, In A '68 Dart, 26" Drag Radials 70% Street/ 30% Strip
So, What Size/Brand Holley Type Carburetor ?
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Re: Need Advice On Choosing Carburetor , New Build
[Re: titan]
#1448278
06/06/13 02:20 AM
06/06/13 02:20 AM
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Joined: Jan 2003
Posts: 5,486 SoCal
Brian Hafliger
master
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master
Joined: Jan 2003
Posts: 5,486
SoCal
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850 double pumper, or QuickFuel 850.
Brian Hafliger
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Re: Need Advice On Choosing Carburetor , New Build
[Re: titan]
#1448281
06/06/13 10:48 AM
06/06/13 10:48 AM
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Joined: Jan 2003
Posts: 12,108 Benton, IL.
DaveRS23
Special needs idiot
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Special needs idiot
Joined: Jan 2003
Posts: 12,108
Benton, IL.
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The double pumpers are a race oriented carb and are very, very rich for street driving. They work good but will wash down your cylinder walls and foul your oil without a good bit of re-work on the transition and cruise circuits. 850 is a good CFM range for 451". But a more street oriented carb would be better suited to the majority street time the car is intended for. Either way, some tuning will be in order. But a street carb should be closer OOTB than a race carb for a predominately street car.
Master, again and still
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Re: Need Advice On Choosing Carburetor , New Build
[Re: Dodgem]
#1448285
06/06/13 08:53 PM
06/06/13 08:53 PM
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Joined: Jan 2003
Posts: 12,108 Benton, IL.
DaveRS23
Special needs idiot
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Special needs idiot
Joined: Jan 2003
Posts: 12,108
Benton, IL.
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Quote:
There is nothing wrong with an 850 DP with stock jetting as new! Carbs are calibrated to give 12.5 to 13. to 1 AFR at wide open throttle and 14ish at part throttle. carbs do not know what is under them only how much air is being pulled through it.
Anyone who washes the walls has problems and no crab tuning and fixing skills. washing the walls would indicate floats to high, blown power valve, bad gaskets and so on.
870 is a good choice if you intend to do some racing then I would lean to a 850 DP. new or at least properly rebuilt and set up.
many get a carb then their expert buddies talk them into jetting it up 10 sizes cause it's a "race motor" I could tell you stories.
Have you ever plugged in a wide band while running an 850 DP? There is no way they cruise in the 14s OOTB.
Most of the carbs we are talking about will be 13ish at WOT, so that is not an issue with either a street or a race oriented carb.
What do you think is the difference between a race oriented and a street oriented carb? Nearly all carb companies build carbs for street duty and other carbs for the track.
There is a reason for that. Most of our street cars (not all, but most) will like 14.5-14.7 for a cruise ratio. And on the cruise circuit is where a street engine spends a good part of it's time. Even most of the street carbs will start a little on the fat side of that just for safety's sake.
But any race/track oriented carb will be considerably fatter than that. A lot of times in the 13's at cruise. And that will wash down the walls and foul the gas. Guaranteed!
Bottom line: either style of carb can be made to work good. One will just start off a lot closer than the other.
Master, again and still
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Re: Need Advice On Choosing Carburetor , New Build
[Re: DaveRS23]
#1448289
06/07/13 02:58 PM
06/07/13 02:58 PM
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Joined: Aug 2003
Posts: 43,204 Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,204
Bend,OR USA
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Quote:
The double pumpers are a race oriented carb and are very, very rich for street driving. They work good but will wash down your cylinder walls and foul your oil without a good bit of re-work on the transition and cruise circuits.
850 is a good CFM range for 451". But a more street oriented carb would be better suited to the majority street time the car is intended for.
Either way, some tuning will be in order. But a street carb should be closer OOTB than a race carb for a predominately street car.
Holley has made many different jetting and circuit changes on a lot of there HP DP carbs, the 4781 in particular. I have three of them now, a 4781 no dash #, a 4781-2 and a 4781-7. The -7 is a lot better at part thtrottle on my wideban than the other two. As I agreed to on Brian post, a new 4781 with the curent dash # should be awesome, the Holley 950 HP works very well on the street also
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Need Advice On Choosing Carburetor , New Build
[Re: Cab_Burge]
#1448290
06/07/13 09:35 PM
06/07/13 09:35 PM
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Joined: Jan 2003
Posts: 12,108 Benton, IL.
DaveRS23
Special needs idiot
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Special needs idiot
Joined: Jan 2003
Posts: 12,108
Benton, IL.
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Quote:
Quote:
The double pumpers are a race oriented carb and are very, very rich for street driving. They work good but will wash down your cylinder walls and foul your oil without a good bit of re-work on the transition and cruise circuits.
850 is a good CFM range for 451". But a more street oriented carb would be better suited to the majority street time the car is intended for.
Either way, some tuning will be in order. But a street carb should be closer OOTB than a race carb for a predominately street car.
Holley has made many different jetting and circuit changes on a lot of there HP DP carbs, the 4781 in particular. I have three of them now, a 4781 no dash #, a 4781-2 and a 4781-7. The -7 is a lot better at part thtrottle on my wideban than the other two. As I agreed to on Brian post, a new 4781 with the curent dash # should be awesome, the Holley 950 HP works very well on the street also
The part throttle and cruise has always needed the most help on the 850DPs I have tuned. It is good to hear that Holley addressed that issue. I haven't had one of the new ones on my wide band, but if they have gotten the cruise in the 14+ range, then that would obviously be a good choice.
I agree that a 950 would not be too much either. I run a 1050 Dom on my street/strip 499 wedge and it cruises at 14.5+/- after a good bit of work.
Master, again and still
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Re: Need Advice On Choosing Carburetor , New Build
[Re: Darryls-Demon]
#1448292
06/07/13 10:43 PM
06/07/13 10:43 PM
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Joined: Feb 2005
Posts: 4,314 Prospect, PA
BSB67
master
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master
Joined: Feb 2005
Posts: 4,314
Prospect, PA
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Quote:
I have a Holley 950 Ultra HP part #80676 on my street strip car and I would not recommend one unless you have a wideband, carb needed lots of changes to work right. My understanding is that the new Ultra HPs are even worse, if that is possible. Wish I had enough cash to try a QF carb.
Is it the common pig rich condition is transition, or something else?
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Re: Need Advice On Choosing Carburetor , New Build
[Re: BSB67]
#1448293
06/11/13 12:45 AM
06/11/13 12:45 AM
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Joined: May 2013
Posts: 80 new york
68HEMIRR
member
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member
Joined: May 2013
Posts: 80
new york
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give patrick a call at pro-systems.com a call
BORN TO BE WILD
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Re: Need Advice On Choosing Carburetor , New Build
[Re: 68HEMIRR]
#1448294
06/11/13 10:19 AM
06/11/13 10:19 AM
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Joined: Jan 2012
Posts: 2,652 Stuttgart, Arkansas
rickseeman
master
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master
Joined: Jan 2012
Posts: 2,652
Stuttgart, Arkansas
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I've always ran faster with a carb much larger than all the recommendation charts for the application. Didn't the Boss 302 and Z/28 have a 780 Holley? And you have an engine 50% larger? Obviously, I would have at least a 1050 Dominator on your car.
2011 Drag Pak Challenger
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