73-87 Chevy _ GMC Trucks > Performance

Tuning Help - Running Rich

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clutchfoot:
Hi All,

Long time lurker, first time poster. Love the forum and has helped answer tons of questions I’ve the years. Got my truck about 10 years ago and have worked on/off since

Most recent upgrade was dual Spal fans thanks to help from the forum, I’ll have more questions on finding an ignition source to cut them off (current go off with temp switch) but that’s a topic for another day

I’ve always seemed to run really rich and I’m finally getting around to addressing it.

Detail:
‘85 C-10
Block: 350 SBC bored .060” over
Heads: 487s with 1.60/2.02 Valves
Intake: Holley Street Dominator Dual Plane Intake Manifold
Carb: New Holley Street Avenger 670 CFM 4150 Vacuum Secondaries
Cam: Duration 288/298, Lift .444/.466
Distributor: Street Fire 8362 Vacuum Advance HEI
Spark plugs: R45TS @.035 gap
Timing: Been a while but I recall landing at 14 initial and 36 total
Headers: Flowtech long tubes w/1.5” primaries

Given that info, and that’s it’s running really rich, where is the first place you check?

I was thinking jets but before I mess with the factory carb setup I thought I’d ask, current jets are 65 Primary and 68 Secondary which doesn’t seem wild from what I’ve read.
Floats are set correctly.

Choke has always seemed to work well but might revisit that after some reading

It’s runs pretty well aside from being burn your eyes rich. If I punch it I do get a slight hesitation, my assumption is too much fuel but I really don’t know.

My plugs have about 200 miles on them and are already black and likely fouled.

Appreciate any guidance the group has. Thanks!

JohnnyPopper:
Welcome from SoCal San Diego.

I found an original product called Colortune. Big glass bulb that lets you see your idle fuel mixture in real time and allows you to adjust it to correct mix. Probably 60 years old, made in England.

Plan to use it on a Rocket V8 soon.

The current model is not the same config, but just as effective and more so, given the extra parts for difficult locations:
https://www.gunsonshop.com/contents/en-us/p209_G4074-G4171-G4172-Gunson-Colortune-See-Through-Spark-Plug-Kit.html

Don't know much about Holley carbs, but would proffer that if you can't lean it out by what's available on the unit, there is some defect allowing extra fuel to enter where it's not supposed to.

Keep us posted, we love to learn!

VileZambonie:
Those carburetors are plenty of hood popping attention lovers. I have a cabinet full of them and don't bother with them anymore. In my opinion, go with the sniper 2

bd:

--- Quote from: VileZambonie on September 29, 2024, 04:21:04 pm ---Those carburetors are plenty of hood popping attention lovers. I have a cabinet full of them and don't bother with them anymore. In my opinion, go with the sniper 2

--- End quote ---

This ^^^^^ is good advice!


Nonetheless, have you adjusted the idle mixture screws?  How many turns out from lightly seated are they?  Do you see fuel issuing from the main nozzles at idle?  What is the measured fuel pressure?

JohnnyPopper:

--- Quote from: VileZambonie on September 29, 2024, 04:21:04 pm ---Those carburetors are plenty of hood popping attention lovers. I have a cabinet full of them and don't bother with them anymore. In my opinion, go with the sniper 2

--- End quote ---

Think of all that cabinet space... ;)

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