Belching flames

[slowmotion]

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?

[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....

[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.

[oldandtired]

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

[OneBadGMC]

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.

[OneBadGMC]

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?

[slowmotion]

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.

[OneBadGMC]

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.

[fla1976]

There's an offer that would be worth the money, even if you have to bring a chef!!! :lol:

[mopar1968]

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''

[slowmotion]

We've made some other changes. I had a guy from Dynotech racing engines look at the car. He thinks the timing was going crazy on the 2 step. We welded the weights in the distributor to lock it down. We bought a couple of cheap reducers for the headers. We went from 4"-3". We put a hotter plug in it also. We were going to test last night but other things came up. We'll be going to the UBDRA race Friday.

[chevyfireball]

I'm thinking all them changes are gonna mess you up. How are you going to know what change affected what? And what change fixed the prob?
GOLDEN RULE: ONE CHANGE AT A TIME

[slowmotion]

I'm thinking all them changes are gonna mess you up. How are you going to know what change affected what? And what change fixed the prob?
GOLDEN RULE: ONE CHANGE AT A TIME

We didn't have that kind of time. We had to throw everything at it. We had a big race this weekend and no time to test. The results were...
1st pass the car ran 6.86 @ 93. Slow but no flame show, no hesitation, good pass.
We took off the reducers and the car ran 6.46 @ 103.
.4 and 10 mph increase. Right where it should be running.
The plugs looked lean so we jetted it up.
I got my bell rang on the line when the car launched, stumbled for a milli second and lauched again. Bounced my helmet off the rollbar.
So we leaned it out a little and the car ran good.

Bad news is that some of plugs are still black. They are not reading the same from cylinder to cylinder. Some are fouled and some aren't. We are getting closer but still not right. It seems to be rich on idle. possibly lean on the pass.

One of the problems are we can't get enough passes at Gateway to make many changes. Tuesday nights can be a joke. My brother was there a few weeks ago and made 1 pass in 4 hours. This coming weekend is Monster Mopar. We go straight to Megabucks after that.

[MEMRACING62]

if its not to far ,greatlakes dragaway is open a few nites a week , you should be able to get the passes in you need there to get it tunned.

[slowmotion]

if its not to far ,greatlakes dragaway is open a few nites a week , you should be able to get the passes in you need there to get it tunned.

Thanks for the info but we are near St. Louis. It's at least 2 hours to the next closest track.

[OneBadGMC]

if its not to far ,greatlakes dragaway is open a few nites a week , you should be able to get the passes in you need there to get it tunned.

Thanks for the info but we are near St. Louis. It's at least 2 hours to the next closest track.

Benton is 90 minutes from Gateway.

[slowmotion]

if its not to far ,greatlakes dragaway is open a few nites a week , you should be able to get the passes in you need there to get it tunned.

Thanks for the info but we are near St. Louis. It's at least 2 hours to the next closest track.

Benton is 90 minutes from Gateway.

I forget about that track. I haven't been there since the 80's.

Mapquest from my town 2 hours 4 minutes / 113.31 miles

[slowmotion]

Car runs ok. Still fat at idle. Ken Jones has the carb.
The down side is that at Megabucks I was sitting under the tower with the car idling in nuetral. The planatary gears exploded while sitting still. The tranny is at Transmissions to Go in Arnold Mo. Hopefully I'll get all my parts back in time for the last T&T at Gateway.