Re: Another Carb question...
[Re: Benforsp]
#2413318
12/04/17 11:30 PM
12/04/17 11:30 PM
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Joined: Nov 2003
Posts: 36,040 Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
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Lincoln Nebraska
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It’s a 451 and am running a Holley 950 on it. I’ve tried a number of things but am having trouble with it back firing through the carb when I mash the throttle. This carb ran great on a buddies BBC with similiar cubes and a big solid cam. I'm assuming nothing was changed on the carb from him to you. at what RPM are you mashing it? vacuum leak? at the offending RPM is the carb being delivered enough fuel? A locked dist means no vac adv so no potential rotor phasing issue (near zero vac so a can loses its timing/rotor phasing shifts back CW). can you run it up to the offending RPM in your driveway & mash it & check the squirt? (fuel delivery needs would be less than a driveing mashing but it'd be a start). Keep us posted.
live every 24 hour block of time like it's your last day on earth
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Re: Another Carb question...
[Re: Thumperdart]
#2413464
12/05/17 06:51 AM
12/05/17 06:51 AM
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Joined: Jul 2005
Posts: 153 Bradenton, FL
Benforsp
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For starters, make sure the secondary squirter is not plugged but those need help regardless......... [quote=Thumperdart] Squirters are not clogged. I have gone from a 31 to a 37 and checked to make sure everything was clean.
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Re: Another Carb question...
[Re: Dragula]
#2413465
12/05/17 06:53 AM
12/05/17 06:53 AM
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Joined: Jul 2005
Posts: 153 Bradenton, FL
Benforsp
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ITS LEAN...under load.
I like #45 squirters in everything! It has 31’s up front and 37’s in the back so you think 45’s in front and back?
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Re: Another Carb question...
[Re: BradH]
#2413538
12/05/17 01:08 PM
12/05/17 01:08 PM
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Joined: Jul 2005
Posts: 153 Bradenton, FL
Benforsp
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What model # "950"?
What's the COMPLETE carb tune?
CR?
Cam specs?
Gear, tire, stall speed?
Launch RPM? It's a 0-82951. The engine has 440-1 heads, CR is 11.0 to 1. Pump Gas. Mostly a street car, 4.56 gear, 275/60/15 MT tires, 3800 stall. I haven't really driven the car much. I am just trying to get the carb to respond right then I can fine tune it, but I feel like I am too far off.
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Re: Another Carb question...
[Re: Benforsp]
#2413563
12/05/17 02:05 PM
12/05/17 02:05 PM
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Joined: Jul 2004
Posts: 19,317 State of confusion
Thumperdart
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I Live Here
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State of confusion
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What model # "950"?
What's the COMPLETE carb tune?
CR?
Cam specs?
Gear, tire, stall speed?
Launch RPM? It's a 0-82951. The engine has 440-1 heads, CR is 11.0 to 1. Pump Gas. Mostly a street car, 4.56 gear, 275/60/15 MT tires, 3800 stall. I haven't really driven the car much. I am just trying to get the carb to respond right then I can fine tune it, but I feel like I am too far off. I did one for a BB Chevy and does not have these issues so call me and I will shoot you the tune and compare to yours if u'd like.......
72 Dart 470 n/a BB stroker street car `THUMPER`...Check me out on FB Dominic Thumper for videos and lots of carb pics......760-900-3895.....
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Re: Another Carb question...
[Re: Benforsp]
#2413746
12/05/17 07:15 PM
12/05/17 07:15 PM
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Joined: Jan 2003
Posts: 15,439 Val-haul-ass... eventually
BradH
Taking time off to work on my car
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Taking time off to work on my car
Joined: Jan 2003
Posts: 15,439
Val-haul-ass... eventually
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You still haven't given any details of the cam or the carb's current tune. That doesn't make it any easier to try and help.
The 0-82951 is the "Street HP", right? Check the actual venturi diameter and see if it's 1.38" or 1.56" I've seen conflicting specs, depending upon when the carb was made I guess. The tune would likely vary quite a bit depending upon which size it is.
I have no first-hand experience w/ the "Street HP" stuff. I'd hope that they're "flexible" enough to be tuned to work w/ your combination.
Last edited by BradH; 12/05/17 07:21 PM.
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Re: Another Carb question...
[Re: BradH]
#2413852
12/05/17 09:59 PM
12/05/17 09:59 PM
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Joined: Jul 2005
Posts: 153 Bradenton, FL
Benforsp
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Bradenton, FL
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You still haven't given any details of the cam or the carb's current tune. That doesn't make it any easier to try and help.
The 0-82951 is the "Street HP", right? Check the actual venturi diameter and see if it's 1.38" or 1.56" I've seen conflicting specs, depending upon when the carb was made I guess. The tune would likely vary quite a bit depending upon which size it is.
I have no first-hand experience w/ the "Street HP" stuff. I'd hope that they're "flexible" enough to be tuned to work w/ your combination. Hey BradH, This is from the Holley site. It should be all the same with the exception of the larger rear squirter, accelerator pump change and 2.5 PV's. I'm not with the car at this moment to know any of the air bleed sizes. What other information is needed? Barrels 4 Booster Down Leg Brand Holley CFM 950 Choke None Emission Code 3 Finish Shiny Fuel Gasoline Fuel Inlet Dual Material Zinc Model 4150 Primary Main Jet 84 Primary Power Valve 6.5 Primary Pump Nozzle Size 31 Product Type Carburetor Secondaries Mechanical Secondary Main Jet 84 Secondary Pump Nozzle Size 31 Supercharged Application No Throttle Bore 1.750 inch Venturii Size 1.563 inch Part Number 0-82951
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Re: Another Carb question...
[Re: BradH]
#2413860
12/05/17 10:07 PM
12/05/17 10:07 PM
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Joined: Jul 2005
Posts: 153 Bradenton, FL
Benforsp
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Bradenton, FL
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You still haven't given any details of the cam or the carb's current tune. That doesn't make it any easier to try and help.
The 0-82951 is the "Street HP", right? Check the actual venturi diameter and see if it's 1.38" or 1.56" I've seen conflicting specs, depending upon when the carb was made I guess. The tune would likely vary quite a bit depending upon which size it is.
I have no first-hand experience w/ the "Street HP" stuff. I'd hope that they're "flexible" enough to be tuned to work w/ your combination. http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=739&sb=1Installed straight up with 1.6 ratio rockers to bring the lift up. Cam Detail....
Last edited by Benforsp; 12/05/17 10:09 PM.
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Re: Another Carb question...
[Re: Benforsp]
#2414161
12/06/17 01:28 PM
12/06/17 01:28 PM
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Joined: Jan 2003
Posts: 15,439 Val-haul-ass... eventually
BradH
Taking time off to work on my car
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Taking time off to work on my car
Joined: Jan 2003
Posts: 15,439
Val-haul-ass... eventually
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Hmmm... -> 440-ish cubes with "big" heads that work better on 500+" -> moderate CR -> 260+ at .050" street roller -> limited stall speed -> street-tuned(?) carb w/ 1.56 venturi & downleg boosters ... Starting to look to me like a mismatch of parts, of which the carb is likely one of the "What's wrong with this picture?" items, along w/ the converter being too tight. The carb may be workable, but I'll take a s.w.a.g. that the way it's set up right now is... uh... "wrong". FWIW, the backfire upon WOT acceleration (IIRC what you posted originally correctly) would point me to verifying fuel bowl levels are high enough & accelerator pump passages & pumps are clear and working properly, and then making sure none of the air bleeds are plugged up (dirt or whatever). My (which are usually only worth about $.0125) is to tear it down completely and get (buy/borrower) the proper tools to measure all the circuits & orifices so that you KNOW what the current tune is. Post 'em, and get some feedback on what makes sense to change from there. This is still a pretty basic carb... it can't be THAT effed up.
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Re: Another Carb question...
[Re: BradH]
#2414189
12/06/17 02:08 PM
12/06/17 02:08 PM
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Joined: Jul 2004
Posts: 19,317 State of confusion
Thumperdart
I Live Here
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I Live Here
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Posts: 19,317
State of confusion
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I agree w/Brad.......miss matched parts and not "ideal" however, I've modded a few of those w/excellent results and one friend picked up 500 rpm's and mph in a v-drive boat and the rest complain of traction issues........ If you're handy w/drillin n tapping I will help ya out for a cold beer............
72 Dart 470 n/a BB stroker street car `THUMPER`...Check me out on FB Dominic Thumper for videos and lots of carb pics......760-900-3895.....
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Re: Another Carb question...
[Re: BradH]
#2414200
12/06/17 02:35 PM
12/06/17 02:35 PM
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Joined: Jul 2005
Posts: 153 Bradenton, FL
Benforsp
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Posts: 153
Bradenton, FL
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Hmmm... -> 440-ish cubes with "big" heads that work better on 500+" -> moderate CR -> 260+ at .050" street roller -> limited stall speed -> street-tuned(?) carb w/ 1.56 venturi & downleg boosters ... Starting to look to me like a mismatch of parts, of which the carb is likely one of the "What's wrong with this picture?" items, along w/ the converter being too tight. The carb may be workable, but I'll take a s.w.a.g. that the way it's set up right now is... uh... "wrong". FWIW, the backfire upon WOT acceleration (IIRC what you posted originally correctly) would point me to verifying fuel bowl levels are high enough & accelerator pump passages & pumps are clear and working properly, and then making sure none of the air bleeds are plugged up (dirt or whatever). My (which are usually only worth about $.0125) is to tear it down completely and get (buy/borrower) the proper tools to measure all the circuits & orifices so that you KNOW what the current tune is. Post 'em, and get some feedback on what makes sense to change from there. This is still a pretty basic carb... it can't be THAT effed up. I had the carb apart and physically went through everything. I did not go to the extent of measuring all of the orifices though...I've never actually done carbs to that point.
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