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Author Topic:   Carb Problem
Limited Mod 57
Dirt Forum Racer

Total posts: 86
posted July 11, 2005 07:15 AM  
Holley 3310 on a mild 350 with Vortec heads.
Car has been sitting for 3.5 years.

Removed the sight plugs in the float bowls so we could adjust the foat level. We were able to adjust float levels and the car ran fine, but as soon as I reinstall the sight plugs, carb starts spitting fuel back up through the vent holes at the top of the carb.

Any ideas as to what's causing this?

Thanks
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(edited for clarification & additional information)

[This message has been edited by Limited Mod 57 (edited July 11, 2005).]

[This message has been edited by Limited Mod 57 (edited July 11, 2005).]

leapinlizard
Dirt Freak

Total posts: 402
posted July 11, 2005 08:28 AM  
floats to high, fuel pressure to high, bad float.

ss99
Dirt Maniac

Total posts: 120
posted July 11, 2005 01:48 PM  
Float vent may be clogged. Sounds like your float bowl is venting through the sight plug when it's open.

Limited Mod 57
Dirt Forum Racer

Total posts: 86
posted July 11, 2005 02:18 PM  
quote:
Originally posted by ss99:
Float vent may be clogged. Sounds like your float bowl is venting through the sight plug when it's open.

Makes sense. Unfortunately I don't know enough about these carburators other than bein able to read the instructions and install new gaskets. I didn't even know there were float vents.

Can you describe to me where the float vents are located?

Thanks

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leapinlizard
Dirt Freak

Total posts: 402
posted July 11, 2005 02:21 PM  
Two tubes with a angle cut(usually)sticking up about 2" above the area the air enters the carb.

Limited Mod 57
Dirt Forum Racer

Total posts: 86
posted July 11, 2005 03:31 PM  
quote:
Originally posted by leapinlizard:
Two tubes with a angle cut(usually)sticking up about 2" above the area the air enters the carb.

I believe I know what you're refering to.

Facing the carb from the radiator, they're at the 12 o'clock and 6 o'clock positions, correct? About a #2 pencil size in diameter?

But just thought about something. If they were clogged, wouldn't they have become "unclogged/blocked" when the gas shot out of the top of them?


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[This message has been edited by Limited Mod 57 (edited July 11, 2005).]

[This message has been edited by Limited Mod 57 (edited July 11, 2005).]

KPLugnut
Dirt Forum Champ
Total posts: 1019
posted July 11, 2005 07:49 PM  
Are the floats currently set so the fuel level in the bowl is just a hair below the bottom of the site plug when the motor is idling? Fuel will "shoot" out the vent tubes if your fuel level is far too high, too...so for that matter, how did you set the float level?

KP

Limited Mod 57
Dirt Forum Racer

Total posts: 86
posted July 12, 2005 08:11 PM  
KP, I'm not sure as I was working on another part of the car while the car owner was "adjusting" the floats.

But I think I may know what is the problem.

Just to be on the safe side, I bought 2 new needle/seats. Took the rear bowl off, installed the new n/s, turned bowl upside down and adjusted the n/s until I could just slip a 3/8" drill between the float & float bowl.

Went to do the front and something seemed weird about the way the float was sitting in the bowl.

Anyway, put the new n/s in, tuned bowl over to adjust and the float was touching the bowl. No matter how far into the bowl I screwed the n/s into it. I think the owner had removed the float and bent the tab.

So I think I found my problem. However my next question is, how critical is the squareness or the float to the tab?

I can bend the tab enough so I can get plenty of adjustment travel out of the n/s. And it seems pretty level/parallel to the bowl. But I'm not sure how tight the tolerances are on the whole float arrangment.

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[This message has been edited by Limited Mod 57 (edited July 12, 2005).]

[This message has been edited by Limited Mod 57 (edited July 12, 2005).]

[This message has been edited by Limited Mod 57 (edited July 12, 2005).]

KPLugnut
Dirt Forum Champ
Total posts: 1019
posted July 12, 2005 08:31 PM  
If it was bent THAT much, I'd prefer to see you install a new float, but it's not severely critical as to the tab-to-float orientation as long as you get the float adjusted so that the float seam is parallel to the bowl ceiling when the bowl is upside down, and you wind up with enough fuel flow through the needle/seat to allow the fuel level to be just a hair below the bottom of the site plug hole's threads.
If it's been bent that much, tho, like I said, it'd be safer to just install a new float.
KP

Limited Mod 57
Dirt Forum Racer

Total posts: 86
posted July 13, 2005 02:10 PM  
quote:
Originally posted by KPLugnut:
....If it's been bent that much, tho, like I said, it'd be safer to just install a new float. KP

Purchased today (2) new Oval Track floats (floats with a cut-out/wedge on the passenger side of the float). They will replace the "stock" center-hung brass floats that were in the carb.

As you said (or inferred), better to be safe than sorry


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[This message has been edited by Limited Mod 57 (edited July 13, 2005).]

xhubby
Dirt Freak

Total posts: 376
posted July 13, 2005 05:13 PM  
We had the EXACTLY the same problem 2 yrs. ago. After spending a week & a half, & $200.00, we were told on here to draw our fuel from an alternate source. We unhooked the fuel line from the fuel cell, & put it in our 5 gal. fuel jug, & it ran perfect. Found out the fitting into the fuel cell was sucking air.
KPLugnut, You might remember me e-mailing you about this problem. We had just gotten our carb back from you when this happened.

BTW, KP, our car ran perfect last weekend as we won our A-feature from the 5th row. The car still died twice on yellow flags though when he was idleing around the track at about 2000 RPM.

KPLugnut
Dirt Forum Champ
Total posts: 1019
posted July 13, 2005 08:22 PM  
That's great about the win. That symptom now makes me believe there's a plugged fuel cell vent that is causing the stalling, or at least a partial restriction someplace.
Very strange....

KP

xhubby
Dirt Freak

Total posts: 376
posted July 13, 2005 08:43 PM  
Could the vent hose be sucking shut? It's just a piece of fuel line that is open on the outer end.

KPLugnut
Dirt Forum Champ
Total posts: 1019
posted July 15, 2005 08:09 AM  
Yes, it could be a cause for that symptom, for sure. Plus, it's a good idea to put a small breather/filter on the end to keep dirt from getting into the cell...

KP

xhubby
Dirt Freak

Total posts: 376
posted July 15, 2005 09:04 AM  
KP, got to looking at the vent hose, & I really don't think it's been sucking shut. It' way too stiff of material. We also made sure the safety ball valve wasn't stuck shut.The darn motor won't stall in the garage., & so far, it's never stopped running during a heat race. Can the diaphram in the fuel pump(a Holley Performance) be going bad, or do they just go bad all at once?
Symptoms again were: Idling around the track on yellows, in 3rd gear, around 2000 rpms, the motor just dies, as if you shut off the switch. Keep rpm's above 3000 & it seems to run fine.
Limited mod 57, Did you fix your problem?
I kinda stole your post, I apologize.

[This message has been edited by xhubby (edited July 15, 2005).]

Limited Mod 57
Dirt Forum Racer

Total posts: 86
posted July 15, 2005 09:43 AM  
quote:
Originally posted by xhubby:
Limited mod 57, Did you fix your problem?
I kinda stole your post, I apologize.

[This message has been edited by xhubby (edited July 15, 2005).]


Ha Ha. No problem.

As far as the problem. Hope to find out this weekend.

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KPLugnut
Dirt Forum Champ
Total posts: 1019
posted July 15, 2005 10:07 AM  
Fuel pumps do go bad (diaphrams, etc), but I've not seen them "just shut off" the motor as you described. That sure sounds fishy to me, like an electrical short or something, since you haven't mentioned that the motor skips or runs "wrong" as tho it's a carb-related issue (or even fuel related at all. Does it just go from running/cruising fine at 2000rpm to a "click! we're shut off now" type of thing?

KP

xhubby
Dirt Freak

Total posts: 376
posted July 15, 2005 10:42 AM  
KP, Yes. Basically, he puts it like this: Your following a car on a yellow flag, at say 2500-3000 rpm. Then the car in front of you suddenly slows down. You lift off the throttle and "boom" it dies. He said he pumps the throttle, hits the switch, & it fires back up. It seems to be fine at 3000rpm & above. The thing that prompted us to initially think "fuel prob." was 2 weeks ago when it fell on it's face while racing. He said it just acted like it suddenly flooded the carb as he came out of turn 4. He had it to the floor, & it suddenly felt like he had another car tied to his back bumper with it's brake on. He pumped the throttle, put it to the floor, & it still did the same thing. Then it went away as fast as it came, & ran 16 laps perfectly. Could an MSD modual in the dist. go bad, & cause this "shutting off" problem? I can't figure out what would make it die at low rpms on the track, but idles fine in the garage. AAAHHHHHH, I HATE MOTOR BUGS!!! LOL. Thanks for taking the time to help, as I'm not much of an engine guy as you can probably tell.

Limited Mod 57
Dirt Forum Racer

Total posts: 86
posted July 15, 2005 10:49 AM  
quote:
Originally posted by xhubby:
I can't figure out what would make it die at low rpms on the track, but idles fine in the garage.

Therefore a load (load on motor) related problem.

(Just trying to help you diagnose the problem)

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KPLugnut
Dirt Forum Champ
Total posts: 1019
posted July 15, 2005 11:26 AM  
Ahhh....yes....MSD....Major Skippy Distributors....

I'm not sure, but it might not hurt to try sticking just another stock distributor in there and see what it does....or at least a "normal" HEI module.

KP

xhubby
Dirt Freak

Total posts: 376
posted July 15, 2005 02:43 PM  
KP, I take it that your not a big fan of MSD ignitions. The dist. was purchased & installed by our engine builder. This motor has not been touched since it was new. We ran it 4 ro 5 races in 2003, all of last season,(about 20 shows), and 12 nights so far this year. Not a single glitch until now. We did pull some rod & main caps off at the beginning of the year, & the bearings looked like new. Not even any blow by yet.
limted Mod57, your MORE than welcome to jump in with any suggestions. Thanks for any input you or anyone else might have.

xhubby
Dirt Freak

Total posts: 376
posted July 15, 2005 05:11 PM  
My bad, I just found out that it's not an MSD ignition. It's a Moroso dist. with a OEM modual in it that is only good up to 6800 RPM. We normally run between 6800 & 7200, depending on the track conditions. I told you I wasn't an engine guru. LOL.

Limited Mod 57
Dirt Forum Racer

Total posts: 86
posted August 05, 2005 09:03 AM  
Just an FYI for anyone that may have been following this.

Problem casued by dirty elements in the needle/seat area, bowl, etc.

I had taken the carb apart and cleaned it before it's initial run, and had even disconnected the fule lines and blew them out with some compressed air.

But I had NOT cleaned the in-line fuel log. And that was the problem.

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[This message has been edited by Limited Mod 57 (edited August 05, 2005).]

[This message has been edited by Limited Mod 57 (edited August 05, 2005).]

leapinlizard
Dirt Freak

Total posts: 402
posted August 05, 2005 10:19 AM  
Fuel pressure at low rpm's?

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