I have a back fire on nos just as i hit high gear and will roll a flame out the top of carb,250 shot 6lbs fuel pressure 82 jets,iam running 31 degrees on motor with nos on rolling down to 21 degrees when nos appied.is it possible that carb.is running out of fuel and going lean??? At the highest demand,iam running just a touch under 6 lbs fuel pressure on carb lines,fuel pressure OR timing problem???? Or neither???

 

What plugs?
Fuel?

21* is to much timing for 250 shot. IMO.

 

Plugs? Wideband reading? Have you looked at the plugs?

I agree with the above. Especially if the tune isn't dialed in 21* is way too much.

 

wow guys ,did not think that timing was too low ,i going to dyno next week on motor see where im at on the plugs and timing,question does a carb set up take more timing than efi set up or is that a myth??iam carb set up

 

Easy way to find out on the dyno .... add timing until it stops making power.

But motor timing and nitrous timing have nothing to do with each other.
If it likes 32* on motor you still need to start at 15* for a 250 shot.
That -2* for 50hp is bullshit.

 

thanks i was not sure if nos timing was alway off the best on motor timing,now so i start with 15 degrees and keep taking less out till plug reading are right???

 

start at 15* and make 1/8th mile hit.
Probably end up adding a degree or 2.... better to start low and creep up on it.

 

-2* per XX is a guideline for near stock motors on sub 150hp shot sizes.

This has nothing to do with highly modified motors, large shots, or when your pushing the limits of your parts or your fuel. I have no idea why the same people who want to be as safe as possible also want the hottest plug and the most amount of timing in there motor.

Pull MORE timing then you think you need to.

If you didn't have an idea of initial timing, chance are you are not very verse in plug reading. Take your time. Get some help and do a little research. If not, pay someone to do the tuning. Don't just read a forum and hurt parts.

I do not mean to be rude, just direct so you can get on the right track.
Agreed.

Also I was not arguing, Just clarifying for inexperienced users.

 

LOL i run that for a 150 shot. I agree with everyone else on starting at 15 and work your way up slowly. Always best to be safe then to push the limits.

 

82 jets? As in 82n and 82f? If that is correct and you are running it @ 6psi than I'd be willing to bet that it is fat as hell. That combined with too much timing is more than likely your problem. You are leaving ALOT on the table with that tune up.

When I run an 82n jet in mine I usually start out with a 76f jet @ 5.5psi and go from there...

 

82 square on speedtech plate safe tuning, i have seen that plate pic up a tenth going down on fuel side6 to 8 numbers.