I was at the track last year spraying a 150 shot and I heard a loud bang. It wasn't the engine blowing up, but I think it was a nitrous backfire. I think the head may have lifted at the time also because I had some antifreeze on the top of the block in the valley and there was antifreeze around the overflow radiator cap. The vacuum line connection blew out from the the lower intake manifold.
I spray with an NX kit and use PSP nitrous plate. I never noticed any obvious damage. Is what happened the sign of a nitrous backfire and what should I do to prevent it other than going direct port?

 

9 times out of 10, Nitrous backfires are caused by running to lean. Not supplying enough FUEL VOLUME and FUEL PRESSURE will cause it.

Dual 255's pumps just arent enough for a 150 shot and 14-16 psi of boost. If you havent done so, step up to 50#/hr injectors and look into the Aeromotive fuel pumps. They even have some new higher volume ones that drop into the tank.

Always over engineer the fuel system, never under engineer it.

 

Nitrous backfires can be caused by two situations.
1. A nitrous system that is too rich or a system that atomizes the fuel poorly, thus causing pooling or puddling of fuel in the intake manifold.
2. A system that is operated too lean.

Backfires are much less common in dry shot applications.

 

Rob those dual 255 pumps are pretty big for his setup. thats moe then double the fuel of the stock 110 pumps and I knew people spraying 150 shots with a 2lb lower also with no problems. I think he's still got plenty of fuel at this point. If he was going to spray a 250 shot, well yeah then I might upgrade a little more, HEHEHEHE Easter are you running a KB???

How do you have the nozzle facing inside the upper plenum? I always try and locktite that little bastard in there cause it likes to move around on you if you don't. that might be part of the problem if its not aimed properly to let the nitrous and fuel atomize.

 

Easterisland

Was it hot or cold out ? How much fuel pressure at WOT
And give me fuel jet # size__ and nitrous #__ .


JEFF

 

I always thought backfires were caused by the nitrous being activated at to low of a RPM?

 

When you lug A motor it will lean it out.

Jeff

 

This is the reason I don't use nitrous on my truck, I just don't have the time nor the income to be changing head gaskets or replacing a short blocks. I've run nitrous on two other vehicles with zero problems but that thought of tossing a notoriously week rod for for a few tenths just isn't worth it to me. Build a motor for it , get your fuel system up to the task and crank up the jets, if your going to run Nitrous run it big because theres nothing like 250 shot to drop you into the seat. Just my .02 Todd

 

Easterisland's motor should be stout enough for a sizable shot...

 

Are you sure you didn't hit the rev limiter.....my truck looked exactly like that a couple of different times and is why I have the motor out right now......the head gaskets were toast. The detonation was severe enough that it crunched a couple of ring lands on the CP pistons so they are getting replaced.

The last nitrous backfire I saw at the track......it was raining fiberglass hood down on everybody from about 100 feet in the air, it was an awsome site. It blew up the guys intake manifold and even deformed the fire wall of his Chevy.
Dale

 

The last backfire I saw the guy didn't purge after he hooked up his NOS and blew the hole hood off of his mustang. I have it on tape somewhere, I'll see if I can find it and post a link to it. Before he was running 680's in the 8th

 

This is the first nitrous backfire that I have heard of on a Gen2. It is extremely hard for the fuel and nitrous to puddle with the blower sucking in the air so quickly. The only way that I can see it happening is if the nitrous is engaged at too low of an rpm.

 

It did break some rings. This was last year at near the end of an 1/8th mile track run...

I want to make sure I do it right this year. I already have to replace the head gaskets again this year. Stock head gaskets ARP head studs and KB blower at 20psi don't work.

 

Do you have an rpm window switch?

 

I never heard of anyone having this problem before, and I never heard of anyone running an rpm window switch.

That is why I like this forum. Information comes out eventually instead of people having to spend and guess...

Maybe a thread should be started about head gaskets. Which brand, part #, and torque specifications. I thought I had mine right and turns out I didn't torque then exactly perfect and have the correct gaskets to start out with for 20 psi. Time for the engine to come out again...