Calling all gear heads!

[tomme boy]

Have a problem I am going nuts with. I have a 496 Chevy big block with procomp aluminum heads and a Victor Jr intake. Mechanical Camshaft and roller rockers. 11:1 comp. Holley 750 carb. Fuel PSI is set at 6 PSI.

Every time I go to run it will foul the plugs. I will change them out and it will do it the next time I go to get the car out again after it has sat over night.

I have put 2 new carbs, a new ignition. I went from a MSD with a 6al to a Accell HEI. It still does it.

I have had it. It is driving me nuts.

Anyone have an idea???????

[Gofaaast]

What octane fuel you running.

[tomme boy]

93 shell

[labradigger1]

Fouling plugs how? Oil fouled? Fuel fouled? Not firing?
Have you checked your spark with the simple arc jumping tool?
11:1 compression should require higher octane

[tomme boy]

Fuel. Just can not figure out where it is coming from. Almost think it may be pooling on the bottom of the intake.

[Hannibal]

Street or Strip?

[tomme boy]

Both. Mainly street.

[Gofaaast]

Try taking a little timing out of it if you haven't already. 11.1 is really pushing it with only 93 octane. Your cam makes a big difference also. Do some research on dynamic compression ratio if you haven't already. Your aluminum heads and intake are a plus though to try making 93 fuel work. Research what jetting you need in your carb vs what you have.

[edler7]

Try running a plug 2-3 heat ranges colder. Champion suggests 1 range colder for every point of compression increase between 9:1 and 12.5:1 to prevent fouling.

[MaryB]

Carb floats sticking and fuel is seeping in overnight?

[Hannibal]

Well, you need to establish the circumstances under which the fouling is occurring. Drive it (I presume that's how you're getting there?) to the strip, shut it down and pull all plugs ASAP. Put in a new set and drive it on the strip like you just stole it. Again, shut it down and pull plugs ASAP. Put in 1 more new set and drive it (again, I presume) to your hacienda. Pull plugs ASAP and install a new set. In manana, fire the beast up, let it idle for a couple of minutes (if it will) and, yeah, you guessed it, pull the plugs again.
If you haven't identified the source of the fouling by now, well I'd have to ask if this is a new carb or some cast-off.

I prefer to work off solid evidence. If solid evidence is unobtainable, then something is WAY off with the basics.

Plug readings are a time tested method for a reason.

A guy can change parts and spend money 'till the cows come home. But if you don't know why, you're grasping at straws.

Huh. My approach to firearms is identical.

[bob208]

is the carb a double pumper mechanical secondary's or vacuum ?do you have the proper power valve installed ? make shore it is not blown. are the primary blades set right? if not you pull too much vacuum and get leakage from the accelerator pump nozzles. what is your jetting sizes? do you have the right gaskets on the jet blocks?
and the big question has the carb been modified as in holes drill screws put in linkage?

[oneokie]

By fouling, are the plugs sooty or wet? If either you need a hotter unning plug or hotter spark, or both. The higher the static compression, the greater the spark quenching from the compression.

[tomme boy]

Carb is brand new. Have not been touched other than set the float and the idle circuits. The timing is set at 15* initial. And vac adv is hooked up. Have not checked for total adv.

The fuel pressure is the same the next morning as when it shuts off. So if it was leaking down, it should be lower after shutting it off. Going to try shutting off the pump and running it a little before shutting down to check this.

I am bad at reading plugs with unleaded gas. They are black and wet when this happens. Don't think it was the spark as it is doing it with a MSD and a brand new HEI with a Accell super coil. I am running the plugs that Pro-comp suggested for the heads. I went with one set hotter to try and it did the same thing.

This all started when I put in this new motor. I had a 402 with iron heads and the same cam, intake, ignition. I just changed the long block. The new long block has a little higher comp, alum heads with larger runners and valves. I gasket matched both the intake and heads to increase flow. That was it when I put it together.

One thing I an going to try to find this weekend is a new fuel pressure gauge. I want to make sure the old one is reading right.

[Artful]

https://www.youtube.com/watch?v=fiMM2S0aADM
another if you don't like the first
https://www.youtube.com/watch?v=saCDmyiBmb0
don't want to watch a video
http://ngksparkplugs.com/tech_support/spark_plugs/faqs/faqread.asp



Condition
Clues
Probable Causes
Remedies


Normal plug
Brown or grayish- tan deposit on side electrode,
Everything’s fine.
Just clean and regap the plug.


Carbon-fouled plug
Black, dry, fluffy soot on insulator tip and electrodes.
Overly rich fuel/air mixture, dirty air filter, too much driving at low speeds, or idling for a long time.
Switch to “hotter” plug. (The higher the plug number, the hotter the plug.)


Oil-fouled plug
Wet, black, oily deposits on insulator tip and electrodes.
Oil may be leaking into cylinders past worn pistons or poorly adjusted or worn valves.
Clean and regap the plug, or replace it, but find out where the leak is coming from.


Burned plug
Blisters on insulator tip, melted electrodes, burned stuff.
Engine overheating, gap is too wide, wrong or loose plugs, overly lean fuel/air mixture, or incorrect timing
Replace the plug.


Worn plug
Severely eroded or worn electrodes
Plug has been in there too long
Replace the plug.



Is the air-fuel ratio too rich? or is the fuel just dumping in past the carb after shut off? Or oil fouled *(does the wet go away just sitting on the bench or does it stay wet)?

Check for such things as a stuck choke, a heavy or misadjusted carburetor float, a leaky needle valve in the carburetor, low coil output or high resistance in the plug wires.

If it is a single wet spark plug means the plug has not been firing. If not due to engine flooding, the problem may be a bad ignition cable (excessive resistance, shorted or arcing). But wet fouling can also be caused by dirt or moisture on the outside of the plug that provides a conductive path to ground, or by an internal crack in the ceramic insulator that shorts the plug to ground.

Oil fouled spark plug Heavy black deposits with an oily appearance. These are the result of oil entering in the combustion chamber, probably past worn valve guides, guide seals or rings. Switching to a hotter plug may help prolong plug life somewhat, but no spark plug will survive long under such conditions. The only permanent cure to this condition is to fix the oil consumption problem.

Can you take some MACRO pictures of your plugs and post them up?

[RED333]

I am going with smaller jets in the carb, sounds like to much fuel.

[oneokie]

Check the voltage of the wire that feeds the Dist. Should be battery voltage. Does it have an electric choke? If it does, check to see if the choke plate is in full open position after the engine reaches operating temp. Just because something is new does not rule out it being defective.

[rockrat]

Thinking RED333 is on the right track. Too much fuel. You may have poor atomization and a poor burn. I would also try a hotter range plug. You might put hotter plugs, maybe two ranges hotter, in one bank of cylinders , then run it and see how they compare.
What carb are you running?
What is your vacumn reading at idle?

[runfiverun]

I would suspect the carburetor for sure.
I am not a fan of holly just because of issues like this in the past.

you might have the floats set a tick too high and they aren't allowing the trapped pressure to bleed off pushing it through the runways and into the engine, then sucking it up when you start the engine.

you could pull the adjuster when you shut it down and let the gas pressure bleed off and see if it does it the next day.

[tomme boy]

OK just got it running again. Fuel is pouring out the venturi. So I need to go find a new gauge to check this. 6 psi should not be doing this.

[oneokie]

Did you check the fuel level in the bowls with the sight plug on the bowls when you first got it running? Could be defective float/s or needle and seats.
What kind of fuel pump do you have feeding the carb? In tank pump similar to what is used for FI? If it is in tank, are you sure the return line is unobstructed?

[bnelson06]

If it's a holly read the instructions on setting it up. Sounds like the idle mixture screw could go in a few turns.

[tomme boy]

Elec Holley in the rear run through two filters. Fuel cell. 1/2" line run to a regulator. No return line.

Float is set to bottom of brass plug front and back. Here is the newest one on it right now.

https://www.holley.com/products/fuel_systems/carburetors/hp/street_hp/parts/0-82751

[tomme boy]

Been messing with engines and racing my whole life. This one just has me baffled. This is also the first motor that I did not put together myself. I bought it off EBAY from a place out in Cal. All of this started with this motor. The old 30 over 402 I had in it ran like a top.

Once it heats up, it runs awesome! But I have to get it to heat up first. Kind of thinking the rings may have never seated.

[runfiverun]

it's in the carb.
I'd bet the needle seats are leaking and the pump is just pushing fuel right through the carb flooding the engine.
I went through this before, a pressure regulator won't help.[it looks cool though]
I had mine turned down to 0 and still had the problem until I finally pulled everything down, once on top of a dark canyon at 4 am.
I finally just bought an Edelbrock and was done with it.

[Duster340]

Not sure what your gaping the plugs at, but may want to open the gap up a bit. Just a thought.

[popper]

Intake manifold heat riser? Definitely carB related. Bleed on the fuel system? Dripping from the Venturi is bad gasket or fuel pressure, bowel level should be below the port.

[therealhitman]

One more idea...is manifold vacuum low enough with your cam that the power valve is never getting "sucked" shut? Mine are plugged for just that reason on my Firebird and GTO...

[Three44s]

I have a International PUP with a 392 V8.

I took the 4 br. Holley and soaked it and kitted it.

We pulled our hair out over gas pouring into the engine.

We re-set float chambers, blocked the secondary fuel supply and tried everything under the sun and I went to town looking for answers and solutions.

I came home with an Edlebrock 600 cfm and that 1210 4X4 purrs like a KITTEN now!

It turns out the new from the kit power valve was blown ....... one little back fire and you can toss one.

There is a modification that places a check valve ahead of them but when a motor head told me the Holley was a good carb on level ground and I am working on a 4X4 for a RANCH .... well my days of wasting time on a Holley carb came to a screaching HALT!

I am done with Holley and UP with Edlebrock! I hated to spend the $324 out the door but now I am slap happy I did .... and it's still running great after four months! The previous owner said he had nothing but trouble with the old Holley ..... she's practically a hot rod now ......... !

Best regards

Three 44s

[tomme boy]

New holley's you can't blow the power valve. I need to walk away for a few days before I set a match to this whole thing!

[jsizemore]

Maybe this will help:

http://www.huntsmachine.com/383ss01p3.html

I'd bump the octane a little and see how it acts.

[30Carbine]

Tomme boy you have the holley 0-82751 carb right. I put that same carb on my 540 in my Camaro. had the same problems your having. Take the float bowls off pull the needles out throw them over your shoulder, order a set of 6-513 spring loaded off road needles and seats. adjust floats until the fuel is about a 3\16 inch below the site hole. then check fuel psi with know good guage adjust if needed. the stock needles in the carb are junk. I wasted a whole Saturday at the track because of them.