Thread: plug fouling and other tuning problems

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I'm having some driving issues with my blazer. The plugs get fouled all the time and it uses way too much gas. I think I have it tuned but apparently not. It idles very nicely with just a hint of lope with 20"hg vacuum. The exhaust only has a hint of gas smell at idle. At WOT I think it runs lean, because the paint is peeling off the headers, but I don't have much time at the track to T&T. I've only gotten 30 miles out of these NGK V-power plugs and used over 30 gallons of gas. I parked it after a cruise night where I idled around town most of the night and now I can't get it to start again even after cleaning these plugs.

Here are my specs...

'90 S-10 2dr 2wd Blazer
probably 3600# race weight

'97 L29 454 big block 9:1CR
cleaned up stock heads
ZZ502 roller cam 224/234@.050 .527/.544 lift
RPM Air Gap intake
3310 750 vac sec carb w/proform mainbody
1 3/4" long tube headers
3" exhaust thru Dynomax Ultraflows
alternator,waterpump,powersteering

TH350 with shift kit and a few other tricks
Hughes GM25 converter supposed to stall around 2800-3000 behind the BBC
ProStick shifter

Currie 9+ rear curently has 3.25 gears
leaf springs and lakewood slapper bars

5 psi fuel pressure with a Holley blue pump
BG fuel filter
Aeromotive regulator
-10AN line from the cell to the regulator then -8 to the carb.

Here are my questions...

1. What do I use to clean the plugs so I can reuse them? I tried a few things but the carbon is on there good.

2. I only know the basics about carb tuning. Do you think I need to do anything with the idle feed restrictors etc...?

3. Would some dyno tuning with a A/F meter help?

4. Does the Proform main body screw up the stock jetting on the Holley this much?

5. Would converting to a secondary metering block help me out with tuning?

Anyone out there want to help me?

30 gallons in 30 miles!!! You have some serious flooding problems with your carb. It's not jetting or any other tune-up stuff, it's got to be pouring gas in there. Change needle and seats, check float level, and don't drive it like it is, you'll be diluting the oil and washing the cylinder walls.

OK more info. I change spark plugs and now it runs again. I set the timing to 13-14 initial and 34 total and it comes on fast. The vacuum gauge I was using before was faulty and I have a new one. It reads 11"-12" now at idle. Funny thing is when I adjust the idle mixture screws nothing happens. I can turn them all the way in and the vacuum gauge doesn't move and the RPM doesn't vary. If I turn both in all the way the engine runs for about 20-30 seconds as RPMs drop slowly from 700 down to 300 then it dies. The throttle blades are almost closed and no fuel is coming out of the boosters at idle. I have the tech guy at Holley pretty confused. The power valve is good, I took it out and everything seems to be fine with it and it opens. It is rated at 6.5 I wanted to take it out for a drive, but it's getting late.

Anyone have these problems before?

OK I took the carb off and set the primary throttle blades so that the idle transfer slots were "square". I also took the #72 jets out and put in some #68s. I put the carb back on and set the initial timing to 16 degrees.

What is the factory setting for mechanical advance on a MSD Pro billet distributor? I thought it was 21, but to my light it looks like 19.

I still have 12" of vacuum when idling at 700-800RPM, but I have 15" at 1000RPM. The idle mixture screws do work now, but still aren't very sensitive. One thing I noticed with the carb off was that the idle transfer slots were full of carbon. I cleaned them out good and they are extremely rough along the edges. Are all factory Holley carbs like this(sorry this is my first Holley)?

I also noticed something that could be a crack going from the idle tranfer slot down to the bottom of the baseplate. I couldn't tell if it was a crack or not, but I could feel a small ridge. If it is indeed a crack this would cause all sorts of tuning problems right?

How do I put a throttle return spring on the secondary blades after I used the secondary idle speed adjustment screw? My dual return spring doesn't always return the throttle now with the new adjustments. The secondaries want to stay open a bit and then it idles at like 1800 until I lift the pedal with my foot.

Thanks for all the help...

You did mention "Pro-form carburetor body" added to your 3310. Did you add the secondary metering block to it and assuming you did was the secondary metering block configured for idle screws?

I have noticed alot lately that folks are using these proform add-ons without further attention to the idle circuits. Remember that the 2-corner idle 3310 carburetors also have 2-corner idle baseplates which need to be converted over to 4-corner idle use.

I have done tons of applications with 3310 carburetors, specifically bolted to BBCs. From the looks of it your combo is right on, but I think your tune is drastically off. Idle vacuum, when properly tuned should be around 15" with those BBCs. Check again for vacuum leaks (top-end leaning).

If the motor is fresh consider checking the valve lash again. Make sure you're not too tight.

Also make sure you have a good 12-volt source of power. I've seen dead batteries on the dyno become the direct source of headaches when sparkplugs starting fouling and reversion kicking up carbon back through the intake (hence the souty black on the carb and inside of the intake)

Hope that helps some.

~Ty @TLI/TPC

Well I am completely stumped. I bought a new carb(0-9380) and replaced the spark plugs AGAIN. Still won't start. It just ran yesterday.

See more at http://www.cardomain.com/profile/slowride454

I haven't updated the interior pics since I finished the inside. It now has a full interior. Also that is before I changed fuel systems. It now has -10AN line to an Aeromotive regulator, instead of the Holley one in the pics. It didn't maintain good pressure, it would go way too high and the drop too low.

I am soooo relieved and pissed off!!!! I farted around with the Blazer a little while after I put the intake on the wife's car. I adjusted the rear float level and then went to the primary. A must have turned the nut the wrong way because fuel shot out of the vent tube as soon as I turned on the pump. So tried the other way and guess what? Fuel shot out of the vent tube again. I dropped the pressure down to 4psi and cleaned up my mess. I turned the damn key and it started right up. After spending $650 and missing a whole freaking weekend of racing fun!!!! I still think the other carb needs a new baseplate, because the fuel didn't come out of the vent tube, but instead went right into the engine. I'll change oil AGAIN and take it for a ride when I get a chance. I'm going to get a book on Holley tuning, I've never had a high performance double pumper before.