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Old 08-01-2005, 09:16 PM
Too Damn Slow
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plug fouling and other tuning problems

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

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?

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Old 08-02-2005, 06:51 AM
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I would think the reason for posting would be to help you if we could.
with the engine at idle, remove the air cleaner, shine a light in the throat of the carb, see if you see any fuel dripping out of the boosters. If so, fuel pressure is too high, float level or levels too high, trash in needle and seat assembly, butterflies open too far due to lack of enough spark advance.
Don`t just check the primary side, check the secondary side as well. Have you checked the ignition? what color spark are you getting?
Paint peeling off the headers is common, after they get hot and cold a few times factory paint or spray paint won`t stay on. It sounds to me as if your running too rich. Is the vacuum advance connected to a manifold source? what`s the spark timing set at? Sometimes you can clean and reuse plugs, other times you can`t, I`ve cleaned them mostly with a die grinder with a wire brush attachment set at a low air pressure so it doesn`t turn too fast.
I don`t like proform products period, but I`ve heard good and bad things about there main bodies. Set the idle mixture with a vacuum gauge, get it as high as you can and it`s set, if it continues to run rich, you have a problem in one of the areas I mentioned above.
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Old 08-02-2005, 07:53 PM
Too Damn Slow
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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?
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Old 08-04-2005, 07:35 PM
Too Damn Slow
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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...
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