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Carb help! #2733831
01/17/20 10:00 AM
01/17/20 10:00 AM
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Indiana
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dragracer1 Offline OP
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Hello to all my fellow mopar brethren!! up

I am building a 1050 carb w/3 circuit metering blocks on 110 race fuel from scratch and I need some help with some baseline components. My specs are:

408ci SB in my 2900lbs Scamp on 28x10.5 radials with leafs and caltracs.
10.5 to 1 comp.
550 solid lift cam
Super victor intake w/2" super sucker spacer
904 w/trans brake
8" 5500 ptc converter
4.56 gears

I leave at 3100 and shift at 6400

I currently run a 750 double pumper on 110 race fuel with the following setup:

Jets
Front - 80
Rear - 78

50cc pump front and rear

.110 needle front and rear

Notched plastic floats front and rear set with fuel level half way up sight plug at 8.5psi.

The car has gone 6.68 @ 100.75 in the 1/8 with current carb but with a 9.5" 4500 ptc converter.

So what spec parts should I use for a baseline?

Thanks
BP

Re: Carb help! [Re: dragracer1] #2733834
01/17/20 10:18 AM
01/17/20 10:18 AM
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Benton, IL.
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DaveRS23 Offline
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Get a hold of Thumper. Maybe if you buy the parts from him, he will share some of his hard earned knowledge. IMHO, nobody has a better handle on the 4500s than him.


KOS
Re: Carb help! [Re: DaveRS23] #2733842
01/17/20 10:41 AM
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dragracer1 Offline OP
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Originally Posted by DaveRS23
Get a hold of Thumper. Maybe if you buy the parts from him, he will share some of his hard earned knowledge. IMHO, nobody has a better handle on the 4500s than him.
up

Re: Carb help! [Re: dragracer1] #2733846
01/17/20 10:43 AM
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dragracer1 Offline OP
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I did fail to mention that I am running stock volume virgin port 65cc eddy aluminum heads

Re: Carb help! [Re: dragracer1] #2733873
01/17/20 12:32 PM
01/17/20 12:32 PM
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Thumperdart Offline
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First off, why 110 fuel w/that low compression. And that's way too much fuel pressure along w/backwards jetting and several red flags including a 1050 3-circuit on that motor......call me.......760-900-3895 I'll get ya going in the right direction.......

Last edited by Thumperdart; 01/17/20 12:34 PM.

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.....
Re: Carb help! [Re: Thumperdart] #2734639
01/19/20 09:10 PM
01/19/20 09:10 PM
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Irun5snd8th Offline
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What would be your alternative to the VP 110?


AFCO, Rons Fuel Injection sponsored Dodge Challenger Mention Street Lethal Motorsports
Re: Carb help! [Re: Irun5snd8th] #2734650
01/19/20 09:41 PM
01/19/20 09:41 PM
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Puyallup, WA
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StealthWedge67 Offline
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@ 10.5:1 with Eddy heads, you could be running 93 octane pump premium no problem.


LemonWedge - Street heavy / Strip ready - 11.19 @ 119
Re: Carb help! [Re: StealthWedge67] #2734677
01/19/20 10:54 PM
01/19/20 10:54 PM
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justinp61 Offline
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Originally Posted by StealthWedge67
@ 10.5:1 with Eddy heads, you could be running 93 octane pump premium no problem.


I've ran up to 11.4-1 on pump 93, my Dart ran 6.57 in the 1/8 @ 3260# with a 10.8-1 408.

Last edited by justinp61; 01/19/20 10:55 PM.
Re: Carb help! [Re: justinp61] #2734684
01/19/20 11:00 PM
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Irun5snd8th Offline
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The inconsistency of pump premium is not an option in his car.


AFCO, Rons Fuel Injection sponsored Dodge Challenger Mention Street Lethal Motorsports
Re: Carb help! [Re: Irun5snd8th] #2734739
01/20/20 02:03 AM
01/20/20 02:03 AM
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StealthWedge67 Offline
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Originally Posted by Irun5snd8th
The inconsistency of pump premium is not an option in his car.


Care to explain?.... while the owner may choose to buy race fuel, pump gasoline certainly is an option. My experience says it won’t run one lick different with one vs. the other.

To the OP: don’t think twice; call Dom (thumper).


LemonWedge - Street heavy / Strip ready - 11.19 @ 119
Re: Carb help! [Re: Irun5snd8th] #2734842
01/20/20 11:46 AM
01/20/20 11:46 AM
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Thumperdart Offline
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I have a 3430 lb pump gas Chevelle racing on 94 octane running 8.84 at 150+ with a 1250 I built at 572 cubes and 11.4 comp...........


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.....
Re: Carb help! [Re: Thumperdart] #2734859
01/20/20 12:18 PM
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RustyM Offline
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Suggest calling thumper carbs.
High octane fuel in that engine is just costing you hp.
Never run more octane than you need to stay out of detonation.
Higher octane burns slower than lower octane thus, the lowest octane you can safely burn will make the best power.

Re: Carb help! [Re: StealthWedge67] #2734921
01/20/20 02:45 PM
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Irun5snd8th Offline
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I would say I have a fair amount of experience at works and doesn’t work in competitive bracket racing. If you want to put pump gas in your bracket car, have at it. While I’m certain it has enough octane to run his engine, it will never be as consistent.


AFCO, Rons Fuel Injection sponsored Dodge Challenger Mention Street Lethal Motorsports
Re: Carb help! [Re: RustyM] #2735100
01/20/20 11:05 PM
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StealthWedge67 Offline
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Originally Posted by RustyM
Suggest calling thumper carbs.
High octane fuel in that engine is just costing you hp.
Never run more octane than you need to stay out of detonation.
Higher octane burns slower than lower octane thus, the lowest octane you can safely burn will make the best power.


This isn’t exactly how it works. Higher octane fuel does not burn slower, it merely resists ignition to a higher capacity than lower octane fuel will. Once ignited, it burns just as fast. I’ve done specific testing with non-ethanol 93 pump premium vs 100 octane race fuel. It made absolutely no difference whatsoever in my 10.6:1 451. Over the course of 7 races, I switched back & forth day by day looking for any data variation and found zero. I do like the smell it releases better, but that’s not worth 3 times the price to me.

Last edited by StealthWedge67; 01/20/20 11:09 PM.

LemonWedge - Street heavy / Strip ready - 11.19 @ 119
Re: Carb help! [Re: StealthWedge67] #2735111
01/20/20 11:50 PM
01/20/20 11:50 PM
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Cab_Burge Online content
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Fuels, gasoline, alcohol, Diesel, nitro all have a energy rating in BTU per gallon, find the fuel that will make the most heat for your application and get the AFR and tune up dialed in and go faster, no magic on that up work twocents


Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
Re: Carb help! [Re: StealthWedge67] #2735142
01/21/20 01:15 AM
01/21/20 01:15 AM
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Thumperdart Offline
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I remember hearing that leaded fuel needs more timing due to a slower burn rate weather or not true no clue but I did add timing to my motor running 110 leaded and it did like it....


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.....
Re: Carb help! [Re: Thumperdart] #2735189
01/21/20 09:05 AM
01/21/20 09:05 AM
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BradH Offline
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Start with straight 93 unleaded (E0) and it makes best power at X degrees of advance...

Add 10% ethanol, and you'll require more ignition lead.

Instead of adding ethanol, blend in 50% leaded fuel and your ignition timing requirements will change again.

Start with 93 E10 and then blend in 50% leaded fuel... you're working with yet another set of ignition timing requirements.

This doesn't touch on the changes to the AFR that go along w/ the changes in the fuel being used, either. Stoich for straight 93 is around 14.7; 93 E10 is closer to 14.0; 110 leaded is closer to 15.0...

My apology for stating the obvious if everyone already know this stuff... shruggy

Re: Carb help! [Re: Irun5snd8th] #2735191
01/21/20 09:19 AM
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Originally Posted by Irun5snd8th
I would say I have a fair amount of experience at works and doesn’t work in competitive bracket racing. If you want to put pump gas in your bracket car, have at it. While I’m certain it has enough octane to run his engine, it will never be as consistent.

This ties into my last post nicely. If your program demands consistency in your fuel supply, regardless of whether you're running 15:1 or 11:1 CR, that's going to have to come from buying a known product at a premium price compared to the latest tanker truck's load of fuel that ended up in the Sunoco or Shell station at the local shopping center.

I don't have to worry about it, but recognize it can be a requirement for others.

Re: Carb help! [Re: StealthWedge67] #2735243
01/21/20 12:13 PM
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RustyM Offline
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Dear Stealth: Burn rates and evap rates DO matter, its not just the heat produced but, how fast the fuel will burn completely.
There are hundreds of articles on this by a plethora of Manufacturers and racing programs.
We are in the age of some pretty exotic fuels as the additives get more and more complex.
We did dyno testing on our known 512 /10.75 /trick flow heads engine to find out what fuel it liked and, yes, race fuel is certainly most consistent, but the engine made best power at 93-95 octane.
100 octane lost 15 hp, no timing adjustments or carb adjustments would bring that back.
110 race fuel lost almost 25 hp.
89 OCTANE was down as well, even with pulling a little timing, but down less than the 110..
When we talked to VP RACING FUELS we were told that the 93/95 octane fuels do, indeed, have a faster burn rate than the higher octane "simple fuels" .
If we were to go to oxygenated or more exotic ( very expensive ) fuels we could pick up a little power as they do, indeed, have faster burn rates .
We were looking for ways to offset the really bad air quality we have in Texas these days and that is only going to get worse as our humidity levels are going to continue to increase year over year- Da values will only increase.
Its normal in summer here to be at a track 500 ft above sea level but Da at 3500-4000 ft thus, we are constantly looking for ways to offset that, the water molecules displacing oxygen in the air.
Of course Vp recommends a fast burn oxygenated fuel thats correct for the compression ratio/cam profile etc.

Still a bit reluctant on those fuel because of the extra maintenance program required and Dom hasn't put out much info yet on working with these fuels.
All that to say, ( sorry for the long post) every time i talk to Vp racing fuels, burn speed is something they bring up .
Its not nearly as critical in 6500 rpm engines as it is in 10-12 k rpm engines but, is indeed, part of current fuel technologies as far as im told, literature we receive.

Hope this is of some small help.

Re: Carb help! [Re: RustyM] #2735248
01/21/20 12:21 PM
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RustyM Offline
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from Vp Racing fuels:

Too Much Octane

You may have heard the following: “don’t use too high of an octane fuel or you will lose power.” This is a half-truth. Having a fuel with too high of an octane will not cause your engine to lose power. The problem is that the popular components used to make the octane of a fuel higher slows the burn rate and a fuel with a burn rate that is too slow can result in an engine power loss. Of course, that is just typically what happens and it does not hold true for all fuels. As an example, VP Racing Fuels worked with the Scranton Brothers and their turbocharged Pro Class Celica throughout the 2002 season to develop a new fuel blend. This blend was designed to provide 120+ motor octane with the quickest burn rate possible. The result was the VP Import blend which produced six percent more power in the Celica than VP Racing C16.

Energy, Burn Rate and Vaporization

Let’s say we have a fuel that keeps our tune-up from experiencing knock. From this point, we would want to find a fuel that packs the most energy, has a compatible burn rate and has a vaporization characteristic that allows for peak performance.

Racing fuels are essentially blends of anywhere from three to 50 components. According to Steve Burns of VP Racing Fuels, “Putting together a racing fuel is like putting together a salad. There are different types of lettuce, olives, tomatoes and dressings. A great salad is one that complements the engine combination being used.”

Some fuel components add energy value to the fuel, some components are good burn accelerators and some components help vaporization. In general, energy values of different racing fuels are usually within three-to-five percent of each other. The burn rate and vaporization characteristics of different fuels are more likely to vary from fuel to fuel. Burn rates need to be fast enough so that all of the air-fuel mixture can combust in the cylinder. If the burn rate of the fuel is too slow, energy will be lost through the exhaust valve. As engine rpm increases, the amount of time that is available for the burn to take place is reduced. In that sense, a fuel that works well in an engine that revs to 6,000 RPM, may not be the best fuel in an engine that revs to 10,000 RPM.

As for vaporization, here is the ideal scenario: The fuel would enter the combustion chamber as a liquid. The reason you would want it in liquid form is that this would not displace any of the air that could potentially make its way into the cylinder. However, when the intake valve closes and the compression stroke gets under way, all of the fuel should change from a liquid to vapor state. With the fuel in a vapor state mixed with the air in the cylinder, the air-fuel mixture can be ignited and a high percentage of the charge will go from reactants to products.

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