Every time I spray a 200 shot, I burn #7 and #8 plugs. All other plugs look fine. Its a nx single nozzle with 78 n20 and 43 fuel pills. A/F is at 11.5 and only have 18 degrees of timing. Im not sure if fuel is just not reaching the back two cylinders or what?? Here are the mods-

408 - compression ratio around 10.5
Callies magnum xl crank
eagle rods
diamond pistons
ported 317 heads
fast 90/ nw 90
42# injectors
comp cam 23x-24x, 612-615

And this only does it on the 200 shot, 150 is fine... Any suggestions?? Direct port time?

 

Switch to a cooler plug if you are using tr6 plugs

 

ya im using tr6 plugs... should i use 7 or 8's???

 

DEFFINATELY switch to a colder plug

 

Tr7s is what you need.

 

i wouldnt trust a single nozzle for a 200 shot i know ppl do it but maybe go to a plate system... but i have my direct port on my 408 now and i wouldn't use anything else.

 

It's not a "TR7"

The number code on the box is a 7 tho...

 

Id run the 8's....With your compression where its at a 7 would be great for MOTOR. then put in the 8 with a non projected tip.

 

What fuel pump are you running? Please tell me its not stock...

 

Colder would or might help, thoug this will not fix the seemingly lean condition. Going down the neck, a dry would and will give better distribution. I also have gone to DP, though dry. I have had no distribution issues running up to a 300rwhp shot down the neck with the dry nozzles. Fuel drop out is a reality on the front mount wet hits. maybe colder plugs and refrain from going bigger? Make sure you run the best gas you can get as an added safety measure. Depending on how lean, this could be a recipe for a lean back fire, been there done that, lol. Good luck anyway, the 408 and a 200 shot is a beast.
Robert

 

2 walbro 255's, 1 in the tank and 1 in line, with an aeromotive adjustable fuel pressure regulator set at 50 psi at wot.

 

Go Dry.....

 

If you are pulling fuel off the rail and/or t-ing it before the rail and still have stock lines, you are starving the injs of fuel. Not due to pressure but due to the volume of the stock lines.

 

Why would you have the regulator set at 50psi?
Robert

 

was told that the injectors would flow better at 50...

 

All you need to do is go with a 2nd nozzle and you will be fine I think.

 

First varify fuel pressure and make sure its not droping.

If fuel pressure is not droping and you are running a solid 11.5 airfuel across the board those runners are not flowing as efficiant as the others. The best fix would be a directport so that you can individually tune those cylinders.

Tuning wise with what you have you can run a colder plug in those cylinders and richen up your over all nitrous tune untill those plugs start reading right.

The best fix though is to go directport.
Dave

 

How about flowing your injectors and putting the 2 richest ones in the back 2 holes.

Or even buying them with say 5% more for the back two. I know you can buy them like that from racetronics.

 

Fuel pressure is not dropping at all.. I guess the easiest and safest way to fix it is to get a direct port setup with a standalone... I had a direct port on the old truck intake and it worked great.. But since I put the fast intake on it I was just going to stay with a single nozzle. Thanks for the advice.