Long story short:

Bought a truck w/ mild.mod 68' 327ci motor. Has Weind Intake manifold and an AFB CARTER Carb.

After I bought the truck I changed the plugs and fluids - have put about 2,000 mi on the vehicle.


I just went out to do some work on the cooling system and for shits I pulled a plug out to check it. TO MY SURPRISE THE PLUG LOOKS BRAND NEW, The electrode is STILL WHITE - no signs of grey or black at all.

I am afraid I am running WAY TOO LEAN & if I haven't already - I am worried about burning the piston rings or possibly a hole right through the piston!

QUESTION:

I have never had a carbureted automobile (always fuel injected) but have had some experience with carbs from my other toys (jetskis/boats). I know I need to turn a screw/screws on the carburetor but which ones and how much? Is there a highspeed & lowspeed screw I should be looking for?

Does it sound like I need to mess with the screws at all???


I really appreciate any directions or advice anyone can give me. Again I am totally a newb when it comes to carbs...


Thanks in advance.

The mixture screws work only for idle and off idle adjustments. To make any real difference you are going to have to change your jets to a larger size. On the AFB there is a bar across the top that raises and lowers the metering rods as the throttle is opened and closed. You might try adjusting the nut in the middle of the bar (if it has one) to raise the needles a bit. That should richen your mixture, but it depends on the type of metering rods and the amount of taper they have.

I wouldn't worry about it much unless the engine pings. A lot of the new blends of unleaded fuel will not leave much residue on the plugs.

If you were running really lean your carb would pop or backfire when you stick it to the floor under load. But if your really worried about it get a metering kit and use one size smaller rod. Ive got a 350 with a big cam and 1.94 fuelies and i run a edelbrock 600 for better gas mileage, i only had a lean spot in the metering stage, wide open throttle runs fine.

So theoretically what should the spark plug look like? It just kind of spooked me because when I pulled the plug - it looked BRAND NEW and I have at least 1000 miles on it!

White is not the color of brand new plugs. It sounds like you need new jets/rods. The color should be more tan than white, tuning your truck at a dyno is always preferrable, IMHO. If you wheel it, I'd look into a Quadrajet, Truck Avenger, or Edelbrock's new off road carb before you invest time and $ tuning the Carter.

Also, you can damage your motor without detonation. If it burns too hot for too long, like a long uphill grade, you can still melt you pistons.

http://www.dansmc.com/Spark_Plugs/Spark_Plugs_catalog.html

Found this - my plug is even WHITER than #24 listed on that chart.

I NEED TO KNOW HOW TO RICHEN OUT THE CARB. It should just be some screws or something... I don't think I should have to change the metering rod or jets just to richen out the fuel/air mixture...

But your telling me those screws are ONLY for idle and low speed?

I don't think I should have to change the metering rod or jets just to richen out the fuel/air mixture...

Yes, you do :flipoff2:

Okay let me rephrase that...

I haven't messed with the carb settings at all - and when I pulled the old plugs they were a light grey color and had carbon deposits on them (4k-6k miles old). My new plugs have 1k miles on them and look BRAND NEW. I don't understand why it would all of a sudden be running hot or lean and it doesn't make sense that I would have to buy new metering rods or jets just to get it back to where it used to be ???

Here is a good place to start http://www.championsparkplugs.com/sparkplug411.asp

If it doesn't surge or pop, white pluge are fine. GREY plugs are bad so you have trouble. Grey means sputtered aluminum so your fragging your pistons. After you richen the jetting, cut the threads off and measure the soot ring, should be 1.5-2 mm wide. Narrow is too lean, wider is richer.

stock setting on you air fuel mixture should be 1 1/2 turns out on both the left and the right in front of the carb.Tighten the screws in until the seat, NOT TIGHT.Then turn both out 1 1/2 turns thats stock setting.When you tighten them count how many turns they were until seat, if less than 1 1/2 probably to lean a mixture.

You aren't going to get an accurate mixture measurement by counting turns. You need a vacuum gauge to do the job properly.

I used to tune carburetors at the track for friends, and I used to raid the junkyards for metering rods and jets for Qjets and AFB's. You can swap metering rods without having to pull the carb apart.

BTW, what heat range are your new plugs? You might want to go with a colder plug.

Kripes,!

1) Setting the idle air screws won't change this guys jetting...anywhere but idle, and thats not where its eating pistons.

2) Changing the heat range won't keep the pistons together...if it greyed the first set of plugs, it will continue to melt aluminum nomatter what plug you pick. Changing the plugs doesn't change the combustion temp, it changes the electrode temp.

Wish I could help more with the AFB but I only know Holleys

Just making sure that he didn't put in a plug that was a couple ranges too high, it's happened before. A hot plug in a normal running engine is going to look alot whiter than a cooler plug will.

Oh yes, I see.

I was just helping with air fuel mixture not jetting. Figured the metering stage might help, sinse the metering rod swap on a afb is about 2 minutes, try smaller diameter on metering rods. replying to traveller i only use the vacuum guage to check the metering springs, use a air fuel sensor in tailpipe for proper adjustments