Belching flames

Old 08-30-2009, 05:24 PM
  #1  
slowmotion
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Default Belching flames

My car has developed a problem. Sometimes, not always, after doing a burnout I stage the car. Then the top bulb comes on, I release the delay box button and stab the gas. A huge ball of fire rolls out of the scoop and the car dies. I refire the car and it runs like it never happened. It is a very mild 468. Hydraulic cam, holley 750, edelbrock dual plane intake. It seems to do it when the engine is cold. So I tried staging at a higher temp. That helped until we raced this weekend and the air temp was cooler (50's-60's). It did it's "Puff the magic dragon" fire show 2 out of 4 runs. I had the carb worked on last winter and it was fine until this fall. The guy that worked on it said it might be a little lean but now both sides of the car are coal black.
We are going to take it off, change the jets and probably remove the power valves.

Any other sugestions?
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Old 08-30-2009, 07:44 PM
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dparker
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Your lean, but at idle.....don't change your main jets yet.....turn your idle screws in 1/2 a turn and see how that does.....also go bigger on your squirters....the reason it got worse when it was cool was because you were lean again....if you have screw in air bleeds go down 5 sizes at a time on the idle bleeds....
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Old 08-31-2009, 03:00 AM
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slowmotion
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Thanks for the advice. We'll give it a try. We kinda thought it was lean but like I said the headers and car are black like it's fat. That's what was throwing us off.

One other thing the headers are too big for the car, but that's what came with the car.
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Old 08-31-2009, 09:40 AM
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Originally Posted by slowmotion
One other thing the headers are too big for the car, but that's what came with the car.
That is leaning you out as well. Do they glow red during the run? Dave
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Old 08-31-2009, 10:20 AM
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OneBadGMC
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Originally Posted by dparker
Your lean, but at idle.....don't change your main jets yet.....turn your idle screws in 1/2 a turn and see how that does.....also go bigger on your squirters....the reason it got worse when it was cool was because you were lean again....if you have screw in air bleeds go down 5 sizes at a time on the idle bleeds....
In???? In on the carbs I have are lean, not rich. He wants to turn them OUT.
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Old 08-31-2009, 10:27 AM
  #6  
OneBadGMC
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Originally Posted by slowmotion
Thanks for the advice. We'll give it a try. We kinda thought it was lean but like I said the headers and car are black like it's fat. That's what was throwing us off.

One other thing the headers are too big for the car, but that's what came with the car.
You probably have several issues going on at once.

Just because it's lean at idle and when you nail it doesn't mean it's not pig fat when it's on the main venturi.

Tune one part of the carb at a time.

Idle = Good idle quality

Squirters/Pump Shot/Pump Cam = transition from the idle circuit to the main circuit. Too little can cause lean hesitation or in bad situations, backfiring. Too much will cause it to blow black/blue out the pipes when you hit the go peddle.


You can call it being methodical, or just lack of experience... either way, it takes me about 6-8 hours to fine tune a carb if I do it on the street.

I will disconnect the secondary linkages, and concentrate on the primary side. When it's done, hook them back up and start tuning more on the secondaries.

Without isolating and tuning each side of the carb separately, you can chase yourself all day long.

I'm assuming you're footbraking this? Have you ever tried a T-brake and 2-step? Can you ease it up on the two step, then floor it and get a clean 2-step out of it, or does it pop/bang while on the 2-step?
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Old 08-31-2009, 03:10 PM
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slowmotion
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Originally Posted by OneBadGMC
I'm assuming you're footbraking this? Have you ever tried a T-brake and 2-step? Can you ease it up on the two step, then floor it and get a clean 2-step out of it, or does it pop/bang while on the 2-step?
No, On the 2-step. Sometimes it's clean and runs perfect and then once in awhile it pops.

We pulled the carb off tonight.

It's a 4150, pn 8106B

70's in the front with a powervalve.
74's in the back with a block off.
The front squirters are 28's
The secondaries are 31's

Thanks for all the tips everybody.

We have a pair of squirters that are 32's

We'll probably block off the other powervalve also so if it does backfire again it won't knock it out.

I think my brother has been talking to Ken Jones.
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Old 08-31-2009, 04:26 PM
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Pinky is good.

If you wanna pay my way into the track and throw some grub down my neck, I'll come down to Gateway and help you out.

70 main jets are pretty damn small, even for a mild 468...

Ditch the PV and put 74 square in it...

throw the 32 squirters up front.

That should help out a bunch.
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Old 08-31-2009, 04:31 PM
  #9  
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Default GAteway

There's an offer that would be worth the money, even if you have to bring a chef!!! :lol:
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Old 09-15-2009, 08:17 PM
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If this helps any i run a 750 on my car, 440 cid small block, It is 76 square on jet's, both power valves blocked, 34 squirters, front and rear.


''JUST MY TWO CENT'S WORTH''
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