New sbc 400 blueprint engine keeps fouling plugs with gas

[HEG77k10]

I have a new blueprint engines 400 Chevy in my k10 and so far it’s fouled 3 sets of plugs. It had started missing after I drove it for a while so I checked the plugs and they were all black and sooty and smelled heavily like gas. The first thing I did was installed a fuel pressure regulator between my mechanical fuel pump and Holley 850 carb and set it around 6 psi. This is my first time doing a build and didn’t think to put in a regulator to begin with. So new plugs and regulator, it ran good for while then started missing. Then I replaced those plugs and and hooked up a pcv valve. After one 10 minute drive the plugs were black again. I’m at a loss and getting kinda frustrated. Also the timing is set at 34 total and 14-16 initial. Hopefully someone on here had the same problem and knows how to fix it haha. Any advice would be very appreciated.

 

[Bextreme04]

I have a new blueprint engines 400 Chevy in my k10 and so far it’s fouled 3 sets of plugs. It had started missing after I drove it for a while so I checked the plugs and they were all black and sooty and smelled heavily like gas. The first thing I did was installed a fuel pressure regulator between my mechanical fuel pump and Holley 850 carb and set it around 6 psi. This is my first time doing a build and didn’t think to put in a regulator to begin with. So new plugs and regulator, it ran good for while then started missing. Then I replaced those plugs and and hooked up a pcv valve. After one 10 minute drive the plugs were black again. I’m at a loss and getting kinda frustrated. Also the timing is set at 34 total and 14-16 initial. Hopefully someone on here had the same problem and knows how to fix it haha. Any advice would be very appreciated.

Have you adjusted the carb at all? Mixture screws? Checked float level? Changed jets? What is your vacuum reading at idle?

 

[Bextreme04]

The obvious answer is... if its running that rich you need to dial in the carb

 

[HEG77k10]

Yeah I’ve done lots of tuning on the carb, haven’t messed with jets tho. It actually is running pretty lean with both floats below middle.

 

[HEG77k10]

would running the stock fuel lines have anything to do with it? The return line is pretty small 1/4 hardline.

 

[Bextreme04]

Its not the fuel lines. I would almost guarantee you just need to get the jets right. I don't see how you could have done lots of tuning without changing any jets... the engine is obviously pig rich to foul the plugs like that. What is your idle vacuum? Did this carb come with the motor?

 

[HEG77k10]

The carb came with the motor, i will go double check the idle vacuum.

 

[Snoots]

It actually is running pretty lean with both floats below middle.

With black fouled plugs? I don't think so.

 

[HEG77k10]

Sorry I meant leaner than the original setup.

 

[richard A lindner]

850 is big need a 650 is plenty

 

[Bextreme04]

850 is big need a 650 is plenty

He is saying that this is a new Blueprint Engines 400ci. Its a big motor. All of them come with a tuned carb and an engine dyno sheet showing they hit AT LEAST the advertised numbers, which in this case is 508hp... I'd say 500hp is not going to be happy with 650.

I'm assuming it's this one? https://blueprintengines.com/produc...ck-gm-dressed-longblock-carburetor-bp4002ctc1

 

[HEG77k10]

Yessir that one

 

[Bextreme04]

That's a whole lot of cam and compression for a truck. I'd bet it's going to be really hard to dial in the part throttle fuel mix. Its probably running pig rich because the factory carb tune is trying to keep it out of detonation and provide enough fuel at WOT. It's going to be really hard to dial that beast in without an AFR gauge and a dyno.

 

[HEG77k10]

Anyone you can recommend that’s good at tuning carbs in the Washington/Oregon area?

 

[richard A lindner]

Sorry my 650hp circle track motor on the dyno only took a 750. But it also cost2500 and the builder fine tuned it at the track