ok i changed my pluges from the **72a extended plug to the **71a short plug...ran my car at the track. on the first run i went 6.04 @ 113.90 every thing felt normal...second run i hit the throttle and the wheels started to come up and boom boom boom.n20 back fire caught the fome on fire. checked 2 plugs thay looked ok.what do you guys think........andis it posible to blow up the map sencer.and car ist running right, right now

 

First thing I would look at is the plug/fuel ring and see if ya are running lean. Sounds like a lean back-fire? Have a picture of your exposed porclean?
Robert

 

i can try to get some pics tomarrow after work

 

my friend said thy could see fire ***** flying around the under neath the car.....and it was cought on video ill post it up as soon as i get it

 

Here is the video

http://www.youtube.com/watch?v=BJW-AFWJD88

 

it doesnt sound clean at all.
was hat 2 seperate passes?

whats the tune up? jets? pressure? timing?

 

yes.. and a 300 shot

 

Need more info if you want help.

Jet sizes , fuel pressure, timing?
Motor, trans ?
What rpm are you leaving at?

What changed from the 6.0 pass to the back fire pass? did you pull all the plugs after the backfire?

 

I think he change the nitrous activation RPM from 3100 or so to 2900.

IDK his jet sizes, fp or timing

forged/built 383 lt1, afr cnc heads and a vic EFI manifold. 4 hole throttle body, TH 400 trans, left off idle. IDK stall either.

no didnt pull plugs yet. I would be doing it now if it was me but IDK when he has to get up. LOL

Hope it's not hurt Mike.

 

nothing changed from the 6.0 pass.but i changed my pluges to a diffrent style the day before.same heat range and same gap 032

 

Do you not know the answers to the questions I asked or do you not want anyone to know your set up?
Like I said its hard to help with no information.

Did you go from NGK's to Autolites?

From the video it sounds like you spraying it at to low of an RPM with a tight converter and its just loading up and backfiring... almost sounded like it was bogging down which will = backfire everytime.
Without any info my shot in the dark fix would be to put some timing in it down low, it will help the converter flash and help burn off any extra fuel.

 

Are you data logging? Using stock PCM? If it's not running right, it could be because the plugs are fucked. Either way, I would be doing a compression check at the minimum.

 

383 lt1 afr 210 heads, vic,4150 tbody, th400,3800 stall,370 gear,nx gemini 6 plate,and a progressive......n20 comes on at 2900 rpm at 60% and ramps up to 300 shot in .05 seconds.......im goint to pull all the pluggs and check them,and make shure my stand alone pump is working to. and thay are ngk

 

im not dataloging and its still the stock pcm

 

How much timing do you have in it? What program are you using to tune it with?

 

You need to pull all of the plugs not just 2...

 

Too low of a rpm to be spraying. THAT "might" be the reason for the backfire.

 

Used to have mine come on at 1800 and it never backfired.

With a auto it is just flashing the converter so there is no real load on the motor (almost like banging the nitrous in neutral). Now if the converter is tight and the timing is LOW with a rich tune up it could bog the motor enough for it to pop.

Check rockers and springs also.

 

Where's yours set at now? I feel a little safer with my window set at 3400 rpms.

 

Mine is set at 0. I had 2 backfires a couple years ago, but they were related to valvesprings, not RPM