I do mostly city stop and go with my 57 Tbird. I find the plugs get really sooty and start to misfire.

I have a 312 with a holley 4160 4 barrel. I am running pertonix ignitor and a flamethrower. I try to run it as lean as possible. I do have it advanced 10˚.

I am running autolite 46 Copper core gapped at standard 0.36. Would running an Autolite platinum help?

Also when adjusting the mixture screws-dose the right side mixture screw affect the right bank and left side left bank?





thanks

You may want to check your power valve.  The diaphragm is easily damaged and the result is a overly rich mixture.  Re. the idle screws, each side feeds 2 cylinders on each bank.  If you examine the intake passages, you can see how they are split.  Conventional sparkplugs are just fine for your use.  I prefer Motorcraft or NGK.  The current Autolites are not what they used to be, IMHO.

What is the cfm rating on the Holley?

-Gary Burnette-

Nat - I agree, its sounds like a blown power valve. its an easy repair job for your mechanical guy. One backfire will blow one in an older carb that isn't internally rigged with a check valve for protection.

The intake manifold is split into a "cross H" design where there are two chambers that feed four cylinders each - but they are arranged to be every other one in the firing order. So the firing order is 1-5-4-8-6-3-7-2 .... and 1 thru 4 are down the passenger side and 5 - 8 down the driver side. So, if you draw an overhead diagram you see that the front and rear cylinder of each head are tied together - and they are connected to the two center cylinders on the opposing side. After a fashion - a "cross H".

When you have a carb with a "side for side" problem, the cylinders on one of the "H's".... say 1-4-6-7, can be found rich and the other cylinders normal. I have an old Holley 4160 that someone has screwed up an idle mixture screw on the metering block RH side. It will not answer the mixture screw on that side, runs rich as all get out on four cylinders.

 
 Steve Metzger       Tucson, Arizona

The carb is a newer model 4160 not the original one. It has the power valve blowout protection feature. It is a 465 cfm. I would think that If the power valve was blown turning the screws all the way in the car would keep running?

A blown power valve isn't the only thing that could cause your symptoms.  You do not state the list number of your carb but be aware some late design Holleys had reversed idle mixtur screws. 

Maybe there's too much alcohol in your gas.  Alcohol leaves a black soot on the plugs.  My low compression farm tractors and my stock Model T soot the plugs regularly, we have E10 around here.  A couple days ago Marathon posted an ad in the local paper, saying they "inadvertently" sold some gas in our vicinity with 15% alcohol, and advised not running it in small engine equipment, like lawn mowers, chain saws, roto tillers, etc.  If you have some of that gas in them, do not run them, they could lose power, run fast and overheat.  Marathon will pay to have the gas removed, the system flushed, and fresh gas installed.  Sounds like to me they are selling us E15 and not telling us but got caught by the small engine industry.  Inadvertent my a$$.  

John - "The Hoosier Hurricane"

Hi Guys. I think the problem may have been that the car is running at too cool a temperature. I am still waiting on my heater valve to come in from Casco. I have by passed it for the time being. I am running a 180˚ hi-flo thermostat but it seems forever to warm up. It also still cool out here in Canada. As an experiment yesterday I blocked off the front grill and drove the car around town, The temperature came up much quicker and I would estimate it was runnin just past hlf way on the gauge at least 180 -190˚. The car runs smoother and with more power. I took it out on the highway to try and burn off any carbon. I pulled a few random plugs. The porcelain is a light tan colour. The centre electrode and side electrode are clean as a whistle. There is a light residue of soot on outer shell that surrounds the porcelain. I believe Hoosier mentioned on another post that the with Heater valve bypassed the Heater core is acting as a second rad. I hope this is the case.



Thanks all.