Carburetor tuning is new to me so forgive me for asking basic questions. I pulled a plug on my 292 powered Country Squire and this is what I’ve got. This is after about 5000 miles on new plugs with a new Holley 4010, same as summit carburetor. Car runs excellent but from the look of the plugs it needs some tuning, Where do I start?
you might make sure the choke is working properly, and then play with the idle mixture...which might be a tad rich. Also, let us know when you pulled the plug out--what had the engine been doing the previous 15 minutes? When you adjust the idle mixture you want it as lean as it can be but still idle well, not hesitate when accelerating, and not quit running. Usually, this means that you lean it out until the idle speed starts to slow down, and then go back just a tad richer. Make sure both screws are adjusted the same number of turns as each other.
Thanks! The car had been idling in the driveway for about 20min before moving it back in to the garage. It’s a mechanical choke so I don’t expect that to be a problem
Sitting idling for 20 minutes, I'd expect the plug to look like that....maybe you should take the car for a long drive, then see how the plugs look? But it's a good idea to play with the idle mixture (and idle speed), so you can get it set up to idle and run just right. You can read about doing it, but still you have to get in there and do it, and see what happens, several times, to get it just right.
Adjust with a vacuum gauge… my 292 plugs never look like that in the 10 yrs I’ve had mine; in fact because the fuel today they are very light in color and no soot in the exhaust either. I’ve done many 20 minute warm ups in my garage after repairs or installations (AC etc) and never a load up or black.
It doesn't take much extra fuel to foul spark plugs badly if any of the different carburetor circuits are out of adjustment or defective. To get an accurate plug read on color takes some experience to know what you're really looking at. Tuners use a technique called a "plug chop", by driving at a steady speed on the highway for a while and kill the ignition and coast to a convenient spot to pull over and inspect a plug or two. Fluffy black deposits on the "base ring" means jetting is too rich. The ground strap provides a lot of information on heat range and ignition timing. I would say you need to back up a bit and start with the stock heat range spark plugs ( if they aren't). Oftentimes people look to install "hot" plugs to try and compensate for a carburetor that is way out of adjustment. Check fuel pump pressure output & carburetor float height/fuel height carefully. That's the baseline for the entire carburetor. Power valve # needs to be selected for your particular engine & altitude. If the wrong # for your setup is installed or it becomes defective it will be pig rich.
It is said............you really can't get a 'real' read on spark plugs unless you do a plug chop. Once it idles....goes slow...goes fast...goes 5000 miles....trying to 'read' them is useless. So forget that! Warm it up Plug the vacuum lines going to the carb Turn adjustment screws in until the idle 'just starts' to change sound(you can hear it) Turn " " out " " " " " " " " Turn " " 1/2 way between Just use a vacuum gauge and screw 'em until you get the highest reading! Make sure air filter is CLEAN. Advance distrb. 5 degrees.(Use a timing light... cheap one...not the dial back because they are NOT accurate) Keep advancing the timing until it rattles when going up a hill (or is hard to crank when engine is warm) Then turn the distrib back a few degrees until its gone. There's your tune-up pal !!! 6sally6
The one you show looks like it has a lot of deposits on it ? from what I can see of the porcelain it looks like you have some detonation going on. I would screw a new set in and start fresh. And maybe buy some better gas.
Tuning like this will generally work ok... but on some engines that are resistant to detonation, the timing can be advanced enough to reduce power and not ping..
I can probably do a plug chop on my own street, it’s 3 miles from the end of the road to my driveway with no stop signs between and a 50mph speed limit, so I can make a few laps of the country block, shut her down and coast to my house and right in to the driveway. Unfortunately it’s snowing now so this will have to wait!
When I first got my Y-Block I didn't understand too much about Tune-Ups other than throw parts at it, and nothing about the finer points of plug reading. Plugs were coal black and dripping wet with fuel. Like everybody else at that stage I skipped 3 or 4 pages of Tune-Up instructions and figured a nice new shiny carburetor would fix that. It didn't. Before getting really serious about carburetor tuning and jetting and all that there are quite a frw other things to look at first, make sure the ignition is plussed up, with a good fat hot spark. Good clean tight low resistance grounds and connections, charging system, cap & rotor. Make certain there are absolutely no vacuum leaks, and the ignition timing advance is correct for all RPM levels. Try to use Holley or Autolite power valves, I'm finding that the generic no name valves that come in the cheap kits don't seem to last very long in today's gasoline. Maybe a year or two. When you get a sharp tune going you'll be able to tell when the power valve is shot right away, and the plugs will foul badly. I learned a lot looking at a vacuum gauge needle driving around town and on the highway. What you're doing ultimately is tuning each individual carb circuit independently, or "curving" the fuel mix for your engine. A lot of people will say that because of today's gasoline a carburetor needs to be jetted up. I'm not persuaded that is true at all, because carburetors in general are way, way rich right out of the box. In any case ya gotta give the engine what it wants, not what you think it should want, or what your other brother Daryl did with his engine. The plugs will tell you, they don't lie. Should idle crisply with steady 19" to 21" manifold vacuum and maybe 15" or so just cruising down the highway. A 6.5 or 7.5 power valve should be about right, but before you can decide on jetting see to it that the power valve isn't dribbling fuel on flat ground cruising. Jetting is the first thing you want to look at, but the power valve has to be out of the equation if that makes sense.
Thanks everyone, keep the great advise coming! I really appreciate you guys helping out a guy just starting out
unfortunately no update on this, I took the power steering apart to replace the seals in the ram but had the wrong ones, the correct seals were hard to find and just arrived today so the car has been in stands for a while.
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