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Old 02-12-2010, 11:12 AM
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Fouled spark plugs

Last summer I had a new engine built for my car. It is a 327 4 bolt main block with alum Dart heads, steel crank 11/1 Eagle pistons, Comp Cam with a 750 d.p feed it. The problem is I can't keep the plugs from fouling wettish,black.

I am not a seasoned gearhead. Just a 50 year old having fun with my dream car. I do know the basics but I am too nervous about turning screws on the Holley. Also, the exhausts pipes have the too rich black soot on the insides of them. Since the car is a 59 Corvette, the smell of exhaust even when I drive the car with the top down (which is 99% of the time) is pretty intense. I know these cars have that problem to a degree, but I think this is excessive.

I have tried to check the float levels but the cam is such that the motor shakes and does not give me a true visual reading. The company that built the engine builds Pro Stock drag racing engines and are about 7 hours from me. They are my cousins and did me a favor by building it between racing builds. So I can't take it back to them the every time it needs adjusting. Any help would be greatly accepted.

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Old 02-12-2010, 01:00 PM
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Quote:
Originally Posted by tahats
Last summer I had a new engine built for my car. It is a 327 4 bolt main block with alum Dart heads, steel crank 11/1 Eagle pistons, Comp Cam with a 750 d.p feed it. The problem is I can't keep the plugs from fouling wettish,black.

I am not a seasoned gearhead. Just a 50 year old having fun with my dream car. I do know the basics but I am too nervous about turning screws on the Holley. Also, the exhausts pipes have the too rich black soot on the insides of them. Since the car is a 59 Corvette, the smell of exhaust even when I drive the car with the top down (which is 99% of the time) is pretty intense. I know these cars have that problem to a degree, but I think this is excessive.

I have tried to check the float levels but the cam is such that the motor shakes and does not give me a true visual reading. The company that built the engine builds Pro Stock drag racing engines and are about 7 hours from me. They are my cousins and did me a favor by building it between racing builds. So I can't take it back to them the every time it needs adjusting. Any help would be greatly accepted.
What intake manifold do you have on it. Did you have any issues with backfires at all. You may have blown a power valve in the carb.
Cam specs would also be helpful. If you have an electric fuel pump you can set the floats without the car running. Have the key on and the engine off and let the pump fill the bowls. If it is to high adjust it down and try it again.
A vacuum reading may also help but it may not be relevant if the cam is to radical. Also what are you running for plugs
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Old 02-12-2010, 01:04 PM
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What cam is in the motor?

what is the initial timing at idle?

What is the vacuum rating of the carb's power valve?
What carb? What intake manifold?

What spark plugs are in the heads?

This isn't something that cannot be solved but takes a bit of tuning savy.
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Old 02-12-2010, 01:07 PM
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Quote:
Originally Posted by F-BIRD'88
What cam is in the motor?

what is the initial timing at idle?

What is the vacuum rating of the carb's power valve?
What carb? What intake manifold?

What spark plugs are in the heads?

This isn't something that cannot be solved but takes a bit of tuning savy.
Beat you to most of it
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Old 02-15-2010, 06:16 AM
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Thanks for the replys fellows, sorry for the lack of info. Here is what I have (I hope it is enough)

Intake: Vic Jr low profile
Carb: Holley 750 D.P
Fuel pump: Mechanical - Holley
Dart Pro 1 heads 200cc 64cc
Competition Magnum rockers w/hydroller lifters
Competition Cam w/ .544 lift

I am not sure what the timing is set at. The car is stored away in the garage for the winter. I will get it up and running this spring. I am just bored from the winter and thinking ahead.
Thanks:
Tim
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Old 02-15-2010, 09:11 PM
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You will need to check the ignition advance at idle and total advance. Normally
what's needed is to limit the centrifugal advance, this allows you to add initial
advance to improve idle quality with the big cam.

In addition carburetor modifications may be needed (not just making adjustments)
Depending on the amount of duration in the cam, you might need to drill the
throttle blades to allow closing the butterflies out of the transfer slots. You
can pull the carb and flip it over to inspect the transfer slot exposure.

Another consideration is the quality of the ignition system. Modern setups
like from MSD can help to keep the plugs from fouling.

Last edited by automotive breath; 02-15-2010 at 09:25 PM.
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Old 02-15-2010, 10:11 PM
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Everyone here has given you a good list to start on. I'll add one or two more thoughts. A carburetor is limited on the amount of pressure it will tolerate before the pressure over-powers the needle and seat in the bowl and allows raw fuel to pour into the motor. No modern carburetor needs more than 5 psi fuel pressure at the carb inlet. Put a gauge on the line at the inlet and monitor the pressure. If it exceeds 5 psi, install a regulator that has a return line to the tank.

The other thought is that if the intake manifold gaskets are not sealing properly all the way around every port, the motor can be pulling in oily vapor from the crankcase (internal vacuum leak). You will never find this type of leak using conventional means (spraying a combustible gas around the intake manifold). I'll refer you to a wiki article I wrote on the subject.....
http://www.crankshaftcoalition.com/w...leak,_internal
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Old 02-16-2010, 05:16 AM
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Thanks again fellows. I'll try those things out when the weather breaks a little. Baltimore has had 80 inches of snow this February and so I think the car will remain tucked away for the next month or so. I will report back to you when I get in to it.
Tim
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