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Old 04-13-2013, 08:16 AM
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Weird Edelbrock carb problem

Drive-ablity is great. Went to the track for T-n-T and only made two runs. Both runs at around 6-7k in 1st gear the front carb started shooting gas out of the accelerator pump. This continued through all gears for the rest of the run. Hard to tell if it was shooting out gas or being siphoned out but only done it on the front carb and not the rear. Didn't see anything wrong with the pump. So made the 2nd run and it done the same thing. Running 5 1/2 lbs of fuel pressure. Electric pump.



355 CI
11:1
Comp cams XR292R
Duration @ .050 254 intake 260 exhaust
Lift .582 .588
Edelbrock TR1YX tunnel ram 2 x 750 Edelbrocks
Ported double hump 2.02/1.60 3891462 64cc heads
700R4/3500 stall
3.90:1 ford 9"
Race weight 3257
80% Street/ 20% strip car
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Old 04-13-2013, 08:19 AM
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did you take the top off carb? rotate the carbs? paintedjester just had a similar situation,contact him if he doesnt drop in.
what ets/mph did you get,wounded?
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Old 04-13-2013, 09:12 AM
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Quote:
Originally Posted by vinniekq2 View Post
did you take the top off carb? rotate the carbs? paintedjester just had a similar situation,contact him if he doesnt drop in.
what ets/mph did you get,wounded?
ET's and MPH were 13.82 @ 109.46 and 13.08 @ 106.31. up from the 12.4s from before. 60 ft times (2.5's) really suffered since changing to the 2 750's from 2 450's cause it'll really light up the tires now! Had the ET street radials at 20lbs, may need to go up on pressure? Had the top off the problem carb. Didn't think to swap them around.
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Old 04-13-2013, 10:13 AM
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Usually going up on pressure will make it worse unless you're way too low to start with. May need to look into rear springs, or shocks.
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Old 04-13-2013, 12:03 PM
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Is the choke closing by itself?

Blower scoop? no scoop? Carbs out in the breeze with no air cleaner? Fuel filter? Float setting.
Edelbrock warns against high speed air flowing across the top of the carbs.

Drag radials 14psi.

carter afb tuning manual
www.mymopar.com/downloads/carterafbtuning.pdf

Last edited by F-BIRD'88; 04-13-2013 at 12:27 PM.
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Old 04-13-2013, 12:16 PM
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Missing accelerator pump anti siphon-anti pullover check or shooter gasket or defective -out of adjustment accel plunger-linkage .

The accel plunge travel and and travel end points is critical or it will siphon.

carter afb tuning manual
www.mymopar.com/downloads/carterafbtuning.pdf

Re air cleaners and air flow over the carb
from the Edelbrock tuning manual
quote:
Air Cleaners: Your Edelbrock carburetor was originally calibrated with a low restriction open element air cleaner configuration; a 14"x3" Edelbrock Signature Series unit. It was also
evaluated for proper metering and vehicle performance using a variety of other air cleaner designs and will perform as intended with nearly any reasonable air cleaner design. While the
Edelbrock Performer Series carburetor does not exhibit excessive sensitivity to the air cleaner, there are several guidelines you should follow when selecting an air cleaner:
•Running without an air cleaner is strongly discouraged for a street-driven vehicle. Dirt and varnish will accumulate in critical bleeds and upset the fuel metering. Dirt and debris may
easily get into the fuel bowl through the bowl vents or larger bleeds and cause a multitude of problems.
• Any calibration testing should be performed with the air cleaner in place. Depending upon the air cleaner used, the metering typically will be leaner with the air cleaner in place.
— A large 14"x3" open element air cleaner, such as Edelbrock Elite Series, Signature Series and Pro-Flo air cleaners, offers almost no resistance to air flow. Flow bench results show
virtually no reduction in air flow. Also, this design should cause no change to the fuel metering.
—A 10"x2" open element design will result in some definite air flow restriction but little change to the fuel metering.
— Elements smaller than 10"x2" are more restrictive and have the most effect upon metering. The fuel metering at WOT will be shifted LEANER, especially at higher rpm ranges.
•If you have a dual-purpose vehicle that is sometimes used in competition without an air cleaner, it may be necessary to have two separate calibrations. If you are running a smaller air
cleaner and have optimized the WOT with it in place, do not be surprised to find that the metering shifts RICHER when the air cleaner is removed. This may require you to calibrate the
WOT with leaner Jets and Rods at the drag strip.
•DO NOT allow the vehicle air-stream to blow across the top of the carburetor(s) such as on an open-bodied car or full-bodied vehicle with a tunnel-ram manifold. The flow of air across
the carburetor will result in an upset to the fuel metering that cannot be accommodated by recalibration since the change to the A/F Ratio will be different for every vehicle speed.

Last edited by F-BIRD'88; 04-13-2013 at 12:33 PM.
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Old 04-13-2013, 01:34 PM
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Quote:
Originally Posted by F-BIRD'88 View Post
Is the choke closing by itself?

Blower scoop? no scoop? Carbs out in the breeze with no air cleaner? Fuel filter? Float setting.
Edelbrock warns against high speed air flowing across the top of the carbs.

Drag radials 14psi.

carter afb tuning manual
www.mymopar.com/downloads/carterafbtuning.pdf
BDS blower scoop. Front carb accel pump sets 1.5" below hood cutout, rear carb pump is 2.5 below cutout and no problem with it. It's the Willys in the pic. No filter other than the one mounted by the pump in the back. The pic of intake is without the scoop as I was tinkering on it. Oh, and no choke. I'll try the 14lbs. Thanks for all your help.
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Old 04-13-2013, 10:08 PM
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How did you see/detect that the front carb was spraying fuel out the accelerator pump shooter
when the scoop was on? (as opposed to just pain flooding {float issue}
Check the accelerator pump plunger and check valve for a fault.
Check the float level.
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Old 04-14-2013, 07:47 AM
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[QUOTE=F-BIRD'88;1666184]How did you see/detect that the front carb was spraying fuel out the accelerator pump shooter
when the scoop was on? (as opposed to just pain flooding {float issue}
Check the accelerator pump plunger and check valve for a fault.
Check the float level.[/QUOTE

I can see the pump area of the carb from the seat. There are spacers between the carbs and scoop to get the scoop into the wind. The spacers are 1.5" and 2" the 1.5 being on front. The gas was coming out of the pump, up onto the scoop at an angle such as being pulled by the wind. There was a lot coming out! Up at an angle, down the side of the scoop and onto the windshield. Which may be a hint as to the siphon question as this continued (both runs) until I let off and slowed down. Unfortunately I didn't notice at what speeds this all took place. I can tell you that is was around 6500 and then continued after shifting. Checked the float level, pump etc yesterday. The float level needed adjusted back to the 7/16 required so that may have been it. I have 1" spacers between the carbs and manifold and may need to remove them, or at least the front one to get the carb down out of the siphon area.

Thanks for the "fire" pic!!!!! LOL
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Old 04-14-2013, 10:30 AM
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Ok I see now. It is leaking fuel out of the pump plunger seal on the top of the carb, not out of the shooter nozzles, into the carbs @ WOT.
Or was it also going into the carb too, making the AFR's rich during the runs?
Was the engine misfireing, black exhaust smoke @ WOT too?
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Old 04-14-2013, 11:27 AM
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Quote:
Originally Posted by F-BIRD'88 View Post
Ok I see now. It is leaking fuel out of the pump plunger seal on the top of the carb, not out of the shooter nozzles, into the carbs @ WOT.
Or was it also going into the carb too, making the AFR's rich during the runs?
Was the engine misfireing, black exhaust smoke @ WOT too?
Oh yeah, coming out of the pump hole. AFR's were way lean so stepping up on the jets. It was running strong but can do better with jetting.
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Old 04-14-2013, 11:51 AM
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go up 4 jets sizes all the way around at least. (the jetting may even need more than this..).it nice to start WOT tuning a bit rich
and tune down leaner from there. Much safer.
watch the plugs.

Verify float settings. and fuel pressure at idle and @ WOT This is critical.

I would blend some good 110+ octane unleaded race gas in, while tuning.

How lean were the afrs during WOT? flat lean (all the time) or shifted leaner with rpm speed? or...?
Did the engine stumble ?..or .? plugs appearance?

Remember the O2 sensor will not may not read right with open headers @ WOT
may need collector extensions to read right @ WOT.

The big manifold plenum carb spacers will defenalty require larger main jets all around.
I did not realize it had carb spacers under rhe carbs. This make the plenum volume much bigger, requireing larger main jets.

Last edited by F-BIRD'88; 04-14-2013 at 12:11 PM.
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Old 04-14-2013, 12:00 PM
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Why was the traction so poor? No suspension travel? weight transfer on launch? rear axle squat.
What is the rear suspension and what is it doing?

With the "old school" high front end weight transfer is limited and air gets trapped under the car at speed.
A chin spoiler under the radiator support may help a lot. High speed stability and under hood air flow at speed.

Last edited by F-BIRD'88; 04-14-2013 at 12:06 PM.
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Old 04-14-2013, 12:15 PM
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I found with my edelbrock carbs that the float setting spec is a start point and you have to fine tune it from there to get it just right.
The float setting is critical. It has an effect on every other tuning/jetting aspect of the carb.
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Old 04-14-2013, 12:24 PM
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If you run the little dual air cleaners in the scoop like on the street this will definatly change the jetting
usually richer. It may be more stable with the air cleaners on/ in the BDS scoop. (function as a defuser)

i was not going to use this style scoop on my SBC tunnel ram/edelbrock carb project.
i was going to build my own (fiberglass) scoop. (to allow for and employ some car scoop air flow management (defusing)
so the carbs can function better at high speed. Carbs like to inhale smooth non turbulant air so tnhey can meter correctly. There is more to this than meets the eye.
I never got to finish my tunnel ram project.
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