540 sparkplug issues at idle??? - Team Camaro Tech
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post #1 of 7 (permalink) Old Jan 11th, 08, 08:32 PM Thread Starter
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Location: Newark, Ohio
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540 sparkplug issues at idle???

Just going over th new camaro I just purchased. The motor is a Bill Mitchell 540 and the previous owner just drove the car for 2 years and never really did any tuning maintenance on the car. It has been a bear to start when its cold and it started popping out of the exhaust while it was idleing and getting worn. My good engine buddy told me to pull the plugs, he bet they were fouled and he was right. They were all black from a rich condition but #2 an #4 were extremely dark compared to the rest, and thats the side that was leaving a black spot on my garage floor.

So I installed all new plugs and let the car idle up to 180 degrees and shut the car off. I started pulling plugs #1 and #3 looked great so I went to #2 and #4 and they were black already. I started to think sparkplug wires so I tested the Ohms and I am getting around 900 on #2 so I know its getting spark.

This motor is completely new to me, I haven't even gone around the block yet. I bet the motor has less then 2000 miles on it.

What else should I be looking at? The ignition is a Mallory Unilite and Coil and a Crane Fireball box.

Thanks, Erik

67 Camaro Pro Street, 540 Bill Mitchell Merlin big block, Merlin Aluminum heads, Holley 870, hydraulic camshaft, 2" Hooker Super Comp headers, Mallory and Crane ignition system, TH400, 2600 stahl, Ford 9" w/ 4:10 gears and posi.
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post #2 of 7 (permalink) Old Jan 12th, 08, 12:26 AM
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Re: 540 sparkplug issues at idle???

What kind of intake do you have? Any chance you've got a drip from the carb that is routing a rich mixture to 2 and 4? What about 3 and 5 - are they rich too, but not as much?

Dave
========================
68 Coupe, 350 w/ Edelbrock Performer RPM heads, cam, intake, 700R4, Dave's small body HEI
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post #3 of 7 (permalink) Old Jan 12th, 08, 07:08 AM Thread Starter
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Re: 540 sparkplug issues at idle???

1, 3, 5 and 7 seem fine, the plugs were not bad. The one thing I did notice is after the car is shut off the fuel pressure gauge will remain at 6-7 lbs for a day or so before finally going down. This a fuel cell car but it runs a mechanical fuel pump with pressure regulator. I am not sure if the regulator is keeping pressure on the carb and not draining back down.

I did another ohms test last night and I seem to be able to keep a constant reading on all the wires except #2. It will do an initial reading then not read anymore until I remove and retouch the tester on the wires again. Not sure if this is a problem or not.

Erik

67 Camaro Pro Street, 540 Bill Mitchell Merlin big block, Merlin Aluminum heads, Holley 870, hydraulic camshaft, 2" Hooker Super Comp headers, Mallory and Crane ignition system, TH400, 2600 stahl, Ford 9" w/ 4:10 gears and posi.
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post #4 of 7 (permalink) Old Jan 12th, 08, 02:26 PM
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Re: 540 sparkplug issues at idle???

Some times a thin film of oxidation on the terminals can mess with you while trying to take a reading, but then again you may have a bad connection where the terminal connects to the wire.

There are some pretty crappy wires out there. Some of them have nothing more than a conductive plastic core that often will burn away and create big problems over time. A bad wire can cause the problem you're seeing.

Dave
========================
68 Coupe, 350 w/ Edelbrock Performer RPM heads, cam, intake, 700R4, Dave's small body HEI
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post #5 of 7 (permalink) Old Jan 12th, 08, 08:20 PM Thread Starter
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Re: 540 sparkplug issues at idle???

I installed a new set of plug wires today and the same thing happened. #2 and #4 were black. I am beginning to think it is carb related. I think its time to take the carb off and see. I was also told that a leaking intake gasket could cause the problem as well.

Anybody else have any suggestions as to why #2 and #4 on my 540 are dead rich and the rest are fine???

Thanks Erik

67 Camaro Pro Street, 540 Bill Mitchell Merlin big block, Merlin Aluminum heads, Holley 870, hydraulic camshaft, 2" Hooker Super Comp headers, Mallory and Crane ignition system, TH400, 2600 stahl, Ford 9" w/ 4:10 gears and posi.
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post #6 of 7 (permalink) Old Jan 12th, 08, 08:40 PM
 
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Re: 540 sparkplug issues at idle???

Quote:
Originally Posted by Erik Beckett View Post
I installed a new set of plug wires today and the same thing happened. #2 and #4 were black. I am beginning to think it is carb related. I think its time to take the carb off and see. I was also told that a leaking intake gasket could cause the problem as well.

Anybody else have any suggestions as to why #2 and #4 on my 540 are dead rich and the rest are fine???

Thanks Erik
Are they sooty black? if so that might be too cold of plug. what plugs are you running?
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post #7 of 7 (permalink) Old Jan 14th, 08, 07:06 AM
 
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Re: 540 sparkplug issues at idle???

Since the motor is new, you must check all basics first. Then you will know what your working with, at least then you could really pinpoint the problem. Have you checked timing and compression? You would have to remove the crane CD box in order to check timing (is it steady?) The Mallory setup will then need a ballast resistor when only running distributor and coil. A bad module could effect timinig issues?
Link to test procedure

Could also be an intake gasket leak?
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