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Discussion Starter #1
I have a 302 roller motor in a 67 mustang, I just got it
running but engine wasn't smooth. I put the temp gun
on each exhaust port and #5 is 40-60 degrees cooler
than the other 7 cylinders.

I checked compression first it is good so pulled the plug
and compared to other plugs the spark is weak. I figured
the cap may be bad so swapped new cap and its still weak.

I also swapped plugs and wires and still weak. The ignition
is a stock duraspark dist/MSD 6al and Blaster 2 coil.

any clue what I am running into??????????
 

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I've become a big advocate of leak down tests recently. I have found that a compression check will show you some things, a leak down test will show you things that don't show up in a compression check, especially related to the valves sealing.

I doubt it's the distributor, but I would check the wires closely. Other thing that comes to mind are a leaky injector.
 

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If it is a 1-3-7-2-6-5-4-8 firing order make sure 5+6 are not cross firing. Move the plug wires away from each other.
 

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I have a 302 roller motor in a 67 mustang, I just got it
running but engine wasn't smooth. I put the temp gun
on each exhaust port and #5 is 40-60 degrees cooler
than the other 7 cylinders.

I checked compression first it is good so pulled the plug
and compared to other plugs the spark is weak. I figured
the cap may be bad so swapped new cap and its still weak.

I also swapped plugs and wires and still weak. The ignition
is a stock duraspark dist/MSD 6al and Blaster 2 coil.

any clue what I am running into??????????
Check the grounds, add an extra ground to the heads. Let us know what you find
 

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What type/size plug wires? Ohm out the wire to check resistance. Are you using a spark tester to check spark?? Any sign of tracking inside the cap or corrosion? Did you change the plug to rule out bad plug?
 

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Discussion Starter #17
What type/size plug wires? Ohm out the wire to check resistance. Are you using a spark tester to check spark?? Any sign of tracking inside the cap or corrosion? Did you change the plug to rule out bad plug?
ford racing 9mm wires, I even swapped over a good taylor wire
and it was still the same weak spark. I swapped msd caps and even
switched to a different plug and still same result

I probably have wire 5 and 6 right next to each over so
I am going to start by separating them
 
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