I have a 383 all stroke ls1 with 12.1 compression ported 5.3 heads ls6 intake, ported throttlebody stock mas air flow cam is 248/254 622/612 on a 114, Pacesetters headers ORY flowmaster with a cutout 3600 converter 3.73 12bolt.

Ok when i had the car tuned it only put down 412hp on the motor and 602hp on a 150 dry shot.
Today i went to a dyno party and got two pulls motor was 358.2hp and 402.9tq Nothing changed on the motor air fuel was 13.1 on the 412 pull and 12.0 on the 358 pull. Where did 55hp go? the car feels fine car is 3680 race ready and runs a 6.98 at 100mph in the 1/8 2days ago.

I did a N20 run Now i did have a 150 dry before went 602hp now i have a wet and a dry kit I had a 50shot in the dry and a 150 tnt wet it pulled 610.4 and was lean.

Can someone explain this Is something wrong or what

 

N20 pull

 

Were they both Dynojets? or was one a mustang dyno and the other is a dyno jet?

 

Yes I'm sorry both dyno jets

 

Something changed - the AFR on the motor was 13.1 and is now 12.0?? It shouldn't change like that. Has the car been tuned completely? I would look at getting it tuned completely with a wideband if it has not been.

What about your fuel system? Do you have a bigger pump?

You are going way lean on that new nitrous setup - was that pull the first time you sprayed that setup? If you sprayed it more than that time, you may need to check your plugs to see if they have any electrodes left!

Your headers and intake are choking that engine - a 382 needs to breath! With a cam that big, and decent flowing heads, you need a 90/90 setup and some 1-7/8 headers.

 

Nothing has changed it was fully tuned less than 2 months ago by jeremy from rev extreme and yes that was the first time it was sprayed on that kit the wet kit is on a stand alone low pressure system set at 6.5 psi I'm not too worried about the n20 pull i will tune that out but the NA run has got me I agree it is rich but 55hp from 12.0 to 13.0
We will be doing a 90/90 in the next couple of weeks.

The car has 42lb injectors and a 255 walbro with a booster

 

But why did the AFR change - something is up there. You would be surprised how much being that rich could drop you - might be causing some knock that will pull timing on top of the rich condition. I would find the reason for the richer AFR on the motor and I think you'll find your power - at least some of it.

You will be happy going to a 90/90 - my car picked up over 30 rwhp when I put mine on. I still need the 1-7/8 headers myself - will be getting those on before spring.

I hope you get to the bottom of it and get it straight!

 

You might be only running on 7 cylinders. That would show it down quite and bit and also show it pretty rich.

 

Your long term fuel trims could have drifted to the plus side since your original tune causing your WOT a/f ratio to go more rich. Have your trims checked with a scanner. There are some other possibilities, such as, you are using two different dynos and wide bands. If you were running on seven cyl you would show too lean of an a/f reading with a wide band O2.

 

Looks like you hit it dead on the head after thinking about what BLK02WS6 said I did spray it on the street on the way to the dyno but only for a few secounds I thought i had it set up on the rich side but anyway i pulled the plugs today and # 2 ground strap was gone all other 7 plugs look fine.
I couldnt feel a miss nore hear one but after changing the plugs it runs smoother and pulls alot harder on the wot run.

So does this mean i pulled 610hp on 7 cylinders?

Thanks for your help guys its going back on the dyno this week to get tghe wet kit right i'll post the #s

 

duno if u pulled that on just 7 cylinders or not,but bet it will be alot better now,re dyno and see

 

Get is fixed and get us some new numbers, that should be a stout set up!

 

And get bigger header, I could see you picket up a lot going with a set of QTP's.