[78TAWS6]

My pipes are black and sooty. Does that mean I'm running really rich yet. I have a 17057274 qjet with 77 jets and 52M rods with the apt set at 3.5 turns out. With the motor warm, set at 2000 rpm, tip choke in no rpm change. Take the vacuum advance hose off the rpm drops. Plugs are light brown about 1/8" down on the tip and grayish white below. Did have 73 jets with 45 rods in it and the plugs look like they were running lean.
Thanks for your replies.
Todd

[Goatracer1]

Do you have a cam with a lot of duration and overlap? If yes, you are pushing a lot of unburned hydocarbons out the tail pipes causing the soot.

[PONTIAC DUDE]

If your fat usually the plugs will show it around the outside of the electrode.

Pipes Dry or Wet?

Dry could mean a low voltage to the plug issue.

Wet could mean an oil control issue.

[Brian Baker]

Never seen this soot problem as a result of raw fuel being dumped out the exhaust due to large cam overlap. I've never run a jet larger than a 74 in my Q-Jet on a 462 with a 238 @ .050" cam.

[78TAWS6]

It's a 455 and the cam has 234I and 236E @ 50 and 11 deg. overlap. The plugs are dry and have a light sooty layer at the base of the threads. The pipes are dry. I have a D.U.I. distributor with live wires. The rings are total seal. It has about 800 miles on it.
Maybe try changing jets and rods. Any suggestions?

Thanks for your replies.
Todd

[grandville455]

I run a 223 231 cam on a 108 and i also run 77 jets with 52 rods .. APT is at maybe a turn or so...idles awesome at 750 in gear....Make sure your primary rods are seated during idle may need a less stiff spring under ur primary piston?I run a pretty stiff spring only cause the rhoads let me

[JEFF KING]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by 78TAWS6:
My pipes are black and sooty. Does that mean I'm running really rich yet. I have a 17057274 qjet with 77 jets and 52M rods with the apt set at 3.5 turns out. With the motor warm, set at 2000 rpm, tip choke in no rpm change. Take the vacuum advance hose off the rpm drops. Plugs are light brown about 1/8" down on the tip and grayish white below. Did have 73 jets with 45 rods in it and the plugs look like they were running lean.
Thanks for your replies.
Todd </div></BLOCKQUOTE>

Sounds normal all tail pipes get black and sooty. A lite film that builds up over time can be seen in all cars exhaust pipes. Rich??
How is it running? The colors of the plugs sounds ok. Is it strong smelling at idle or just the normal musclecar smell?

[78TAWS6]

Jeff,
The smells a little strong, but not eye watering. I might try turning in the apt. The pipes are from pypes with the crossover and exchange, about 500 miles on them. It seems to run pretty good, idles at 850 and about 750 in gear.

Just put in some 3.42 gears for next weekend in Minot. I'll see how she runs then.

Thanks for your reply.
Todd

[Half-Inch Stud]

Yea, this reminds me to keep er rich, to carbon coat the exhaust system. That keeps the EXH flow good for many years after.

If there is an issue, your issue would be either:

Need more advance at idle & off-idle.
Attain idle with Pri plate closed, or barely open. Idle mixture screws could get a little lean-out; for best result go 1/2 turn out after the stumble.

Not likely: An actual Pri spring or rod/Jet change. Only ADJ PRI Rod/Jet & Spring to perfect the off-idle and Ping-free pull away.

HIS

[Kenth]

The APT adjustment doesn´t reach the power piston pin until 2 turns from seated.

Even with APT seated the rod will not have it´s widest part in the jet, a 52M rod will act like a 50M rod regarding flow area through the jet.

Try to seat the APT screw or replace the 52M with 54M rods.

[Cliff R]

I'm also using a 17057274 carb with the same jet/rod combination. The APT is just about seated nearly as I can remember. I did size both pairs of main airbleeds to .070", use a .135" fuel inlet seat and the small float set at 9/32". Been running it that way for about 2 years, 15mpg's on the street and the car runs well into the 11's at the track in street trim. I've never gandered at the tailpipes, but the pumper is blackened a bit just above the pipes. Never pulled a plug either, figured it wasn't to far off considering how well the engine runs?.....Cliff

[Brian Baker]

"Live wires"...never heard of that brand of plug wires. Are they the ones that light up? If so, *****can them and get a set of quality 8mm wires.

[78TAWS6]

Livewires are plug from D.U.I. They have a spiral wound core with low resistance of 300-350 Ohms per foot. Read somewhere that they are close to 10mm.

Thanks for all the info.
Todd

[boltbuster]

The source of your black soot may simply be the ethanol in the gas you're burning, assuming that you're using pump gas. If the car runs well and the plugs look good, don't worry about it. I got that tip from my local GTO go-fast guy, and I trust his opinion. For your consideration...

Kerm

[JEFF KING]

Sounds right to me.