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Old 04-13-2013, 09:16 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, 09:19 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, 10:12 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, 11:13 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, 02:34 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 04-14-2013, 08:47 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, 12:27 PM
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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, 01:43 PM
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Quote:
Originally Posted by F-BIRD'88 View Post
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.
Changed the jetting to 3 stages rich. Will go 4 richer as you suggest. Running the street exhaust.
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Old 04-14-2013, 01:54 PM
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Firebird has this covered I can't think of anything to add to what he already stated? LOL

I would ask if that scoop is sealed completely under the carbs or is it the copy cat Hilborn scoop with an open space on the bottom between the carbs? I track tuned a car with the open space on the bottom of the scoop with the Edelbrocks and the front carb was out of wack but when we filled the open space and sealed under the scoop (Good old duct tape) for a test run, it cured the problem! The front carb had high speed air flowing over it and shooting down the opening on the bottom of the scoop While the rear carb wasn't effected in the back of the scoop! That would effect your carb tuneing the next time your at the track to test & tune when your current problem is fixed

But that wouldn't effect your current accelerator pump problem!!

Jester
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Old 04-14-2013, 02:14 PM
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Quote:
Originally Posted by F-BIRD'88 View Post
Did you data log the AFR's on those strip runs?
Why so much different than on the street?

Open headers? air cleaners? or???
I'll try to answer all your questions.
Have no way to verify the pressure at WOT. It's at 5.5 lbs at idle and 5.5 at 6K in park. Attached is a table of the 2nd run AFR's. 1st run was much the same. Includes the burnout, stage and run.
traction: Had the tires (m/t ET street radials at 20 lb.) Not much travel in the front end. 4 bar IC has been adjusted to race weight but sure it could use some more although there is is no way to put more angle to the bars. Could you go into the chin spolier in more detail? Size etc.
Yes, run the little dual air cleaners k&N in the scoop.
3 edelbrock chart tuning stages on the primary jets, both carbs. The AFR's look like they richen up nicely once the secondarys open.
O2 sensor is in the right hand collector 2" from exhaust pipe connecter.
Jetting is now 116 and 71x47 rods. Was 113 and 71x47 rods.Secondarys are 107.
Very little difference in the 2 runs.
1/8 mile:
60ft: 2.5867
ET 8.5863
MPH 89.14
1/4 MPH 106.31
ET 13.0862
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Old 04-14-2013, 02:18 PM
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Quote:
Originally Posted by painted jester View Post
Firebird has this covered I can't think of anything to add to what he already stated? LOL

I would ask if that scoop is sealed completely under the carbs or is it the copy cat Hilborn scoop with an open space on the bottom between the carbs? I track tuned a car with the open space on the bottom of the scoop with the Edelbrocks and the front carb was out of wack but when we filled the open space and sealed under the scoop (Good old duct tape) for a test run, it cured the problem! The front carb had high speed air flowing over it and shooting down the opening on the bottom of the scoop While the rear carb wasn't effected in the back of the scoop! That would effect your carb tuneing the next time your at the track to test & tune when your current problem is fixed

But that wouldn't effect your current accelerator pump problem!!

Jester
Good to know. It's a BDS scoop, no opening as to what u said. Had 2 of those cheapys n didn't like them.
Glad to get your input as I heard u'd had this problem also.
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Old 04-14-2013, 03:13 PM
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Quote:
Originally Posted by F-BIRD'88 View Post
The data is all over the place. is this from your drag testing or a street test?

i don;t see 3 gear changes.

Your 1/8th mile MPH says you let off the gas before th 1/4 mile ended.
Should have could have gone 113 MPH. Got to keep your foot in it.

Why is the idle AFR so lean? should be in the 12.5 to 13.5:1 zone.
14's and 15+ is way too lean.
O2 sensor error at idle??? or ????
exhaust gasket leak???

When you jet a carb for WOT power you should increase or decrease ALL the jets up or down from default base line.
not just the primaries.

Is the distributor locked out? timing?

I don;t see gear changes during the burn out either? or enough rpm.
You want to 1-2-3 shift on the burn out. Let off the brake when you see tire smoke.
Do not sit in the water. drive thru, then start the burnout beyond the water puddle.
Is this a street radial or a real drag radial.?

With a treaded tire you want to avoid the water box all together. Drive around the water box
and back onto the wet pavment/concrete IN Front of the water box.
Normal street radials are useless at the track.

I don;t see a crisp launch.or converter flash . Did you do dog it...walk it out of the hole at part throttle?
Chart is from 2nd run
Idle AFR: thought It suppose to be 14.7 range so adjusted for that. No exhaust leaks.
Do the burnout in 1st with 700r4.
Kept my foot in it but it bogged after launch.
Launch @ 3500
He wet the whole track so couldn't drive around it as I usually do. Never have seen any smoke from the tires and I've burned them til the cars moves sideways. M/T ET street radials.
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Old 04-14-2013, 03:16 PM
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I used to do 3rd gear burnouts and count to 10
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Old 04-14-2013, 03:17 PM
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Quote:
Originally Posted by Fang16 View Post
Good to know. It's a BDS scoop, no opening as to what u said. Had 2 of those cheapys n didn't like them.
Glad to get your input as I heard u'd had this problem also.
Ive been running & tuning tunnel rams and cross rams since the 60s LOL I think they are the best intakes for power on normally aspirated engines and are very adaptable for street use for rodders ( I'm one of the few LOL) I ran high front end fat fendered Gasers! The front fenders are like para shoots and will lift front tires right off the track and you lose your steering at top end! It only takes one time to happen to end your racing in a disaster So be careful and take precautions to prevent it!! Don't take for granted it won't happen because it never happened on your other runs! You have no Idea What you feel when your steering is lost at 130 MPH and your drifting into the other lane or the wall!!!!! There is nothing you can do to slow the car fast enough to get your steering back And your life is in gods hands


Your speeds aren't there yet but as you run you are probably like me and will get the car to run faster and faster and lay awake at night dreaming up ways to get more speed out of it! I drilled 3 inch holes in my fenders and hood to let the air out on some of the Gasers I ran, and some I had louvers pressed in them and the hood!

Be careful

Jester



A suggestion I would Make Is get the spacers out from under the carbs and add tubes to fit the carbs bellow the scoop to raise the scoop into the air stream the increased velocity of the air down the tubes will increase power more then the spacers under the carbs and different length tubes will make differences also in the ram effect!

Last edited by painted jester; 04-14-2013 at 03:35 PM.
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Old 04-14-2013, 03:24 PM
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Quote:
Originally Posted by F-BIRD'88 View Post
I am not seeing a complete drag pass including burnout gear shifts and drag WOT shifts etc.

its is going to be near impossible to track tune with no traction.
It's all there. Do burnouts in 1st gear only. Mostly to just clean the tires. He wet the whole track n couldn't drive around it. M/T says it's usually better to not heat them up to much and this worked last year with the holley 450's but it now seems I have much more power about 3500 with the edle 750's. usually only use 1st n 2nd in a run. 390 gears n 30" tires. Put foot on floor n hold it there to the end. Trip the lights right at 7K in 2nd. At 6500 just push the shifter to 2nd and let it do it's thing.
No traction: yep! burning'em up in 1st now. Good squat and burn.
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