Carbureted LSX forum - Black Black plugs....

Stock 2004+ LS6 long block. Running a Vic Jr and TR5 plugs. Pill 5 is in the MSD box now. Car is a 2000 WS6. Carb is a 780 built to spec by Prosystems. (no I haven't had a chance to call Patrick yet)

Had a racetronix pump in the tank when I bought it. I set the fuel lines up with a Mallory bypass regulator and a fuel Y-block with 6an lines to the primary and secondary bowls separately.

When the engine first fired the return line wasn't large enough and I couldn't get the fuel pressure below 12psi. Ran for 4-5 mins off and on total. Smoked like a diesel it was soo rich. Fixed the return line and now I can get the pressure to hold steady at 3psi on up. Pulled the bowls off to make sure the needles weren't stuck open. Put it back together.

Got the front float set where I want it. The rear float isn't showing in the sight glass and there is fuel spurting out of the rear air horn. While running the car is still rich at 10.5 to 11.5, sometimes I get a reading of 12 before the plugs foul out. Checking the heat in the long tube primaries and the front two are hot and the rear two are cold on both sides. The plugs are no longer wet and black but still dry and black.

I can screw the idle mixture screws all the way in and it doesn't help. I can open the secondary butterfly screw a bit and it will lean out... a bit, but the rpms comes up and over 2000. Lots of smoke and popping out of the exhaust.

Sorry for the long post guys. I'm new to the carb world and have done all I can without outside input. Really don't want to pay to have a shop tune this thing for me.

So even if it seems like a basic thing for you I may have missed it so throw any ideas you have at me.

Thanks for the wonderful forum....

sounds ike the secondary float is stuck

Take plugs out and sand blast them or throw a new set in. I had a similar issue. The plopping out the exhaust. When your car was running with the messed up return line. It wiped the plugs out. Been there. Set fuel pressure at 6.5 . Put idle air screws at 1 1/2 out. Get the throttle plates in line.

Ok, so pull the secondary bowl off and make sure there is nothing thats stuck or snagging. I know I can kinda set the float level with it off the carb. Hang it upside down and set the level right? Should it be around the same level as the primary?

Had a new set of slugs in after I removed the fuel bowls the first time. Thought I had it pretty close. Started with the screws 1 1/2 out and did the same thing.

Take plugs out and sand blast them or throw a new set in. I had a similar issue. The plopping out the exhaust. When your car was running with the messed up return line. It wiped the plugs out. Been there. Set fuel pressure at 6.5 . Put idle air screws at 1 1/2 out. Get the throttle plates in line.

If the plugs are dry sooty black then you are having a similar problem mine did. Once they are sooty it allows the spark to carbon track down into the center of the plug before it arcs to the ground strap. Spark energy is wasted.

The rear float isn't showing in the sight glass and there is fuel spurting out of the rear air horn. While running the car is still rich at 10.5 to 11.5, sometimes I get a reading of 12 before the plugs foul out. Checking the heat in the long tube primaries and the front two are hot and the rear two are cold on both sides.


this ^ is your sign...yes, set the float to be level upside down with the bowl off (good starting point) even if you dont see anything in the needle and seat take it out and blow it off with compressed air.

let us know how it went.

assuming its a 4 corner idle circuit carb DO NOT go 1 1/2 turns out. more ike 1/2 to 3/4 turns.

The rear float isn't showing in the sight glass and there is fuel spurting out of the rear air horn. While running the car is still rich at 10.5 to 11.5, sometimes I get a reading of 12 before the plugs foul out. Checking the heat in the long tube primaries and the front two are hot and the rear two are cold on both sides.


this ^ is your sign...yes, set the float to be level upside down with the bowl off (good starting point) even if you dont see anything in the needle and seat take it out and blow it off with compressed air.

let us know how it went.

So you have gas overflowing the secondary and spilling into the intake and you wonder why it is rich and won't respond to the idle mixture screws?

Not sure I am hearing you right. Sounds like your secondary needle valve is bad, stuck or missing.

Holley has instruction sheets on how to set float levels on or off the car.
http://www.holley.com/data/TechService/Technical/Adjusting%20Your%20Carburetor.pdf

Took the secondary bowl off. Made sure the float moved freely. Using the older bunged up plugs, I started the engine and finally got the float levels right. Now I can lean bog the engine and get it to stall with the mixture screws. Even with the fouled plugs in it it ran better than it ever has and could get my AFRs up over 13 without a problem. Went out to get some new TR5 plugs. It was too late to try and start it. The neighbors like us and I'd like to keep it that way ha. So I'm feeling better and I'll let you guys know how it goes with the new plugs.

I'm still running the pre set pill #5. I know I can get the timing set better with a computer. I'm going to read over the timing sticky to find a setup similar to mine.

Thanks everyone.

:usa: glad you made progress man!