[Quick85]

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??????????

 

[pete9857]

Damaged or rubbing reluctor wheel inside dist.? On no. 5 firing.

 

[tomato]

Ls swap will fix it up

 

[Quick85]

Damaged or rubbing reluctor wheel inside dist.? On no. 5 firing.

dist looks like it has a lot of miles on it, may swap msd dizzy in

 

[Quick85]

Ls swap will fix it up

building car for a guy not wanting a car that is ungodly fast so
that won't be necessary

 

[Topfun99]

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.

 

[KILLER BIRD]

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.

 

[oldschool]

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.

Or make sure they cross at 90 degrees somewhere...

 

[Quick85]

it's an H.O. so I may have 5 and right beside each other also it is a carb motor

 

[pete9857]

The OP said weak spark on no. 5? Has to be electrical?

 

[mrdroptop]

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

 

[Quick85]

I've got it grounded with 2 gauge battery cable
From the head to the frame

 

[turbo88coupe]

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?

 

[1wild383]

THE 302 ROLLER IS A DIFF FIRE ORDER THAN THE CONVENTIOAL! LEARNED THAT LONG AGO! 15426378 I BELIEVE?

 

[nuclearcobra]

No 15426378 is the 302 firing order , the newer 5.0 and 351Windsor plus a few others use the 13726548 order.

 

[1wild383]

right see I did the same thing again!
drove me nutz
I built a 302 ho in a ranger.
thx

 

[Quick85]

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

 

[forced5]

Exsct thing happened to me. Switched out msd boxes and problem gone.

 

[Big T Racer]

Hit the newby thread you phuckstick!!

 

[rmk57]

Could it be the PCV pulling oil into the #5 cylinder?