Spark plug recommendations
Thread Starter
Pro
Joined: May 2013
Posts: 570
Likes: 22
Spark plug recommendations
Need recommendations on replacement plugs for my 69 427.
After warm up and when under a load engine will intermittently miss and run rough. Just had carbs rebuilt and set timing. Wires have been replaced recently. Next easiest thing to try is replacing plugs.
After warm up and when under a load engine will intermittently miss and run rough. Just had carbs rebuilt and set timing. Wires have been replaced recently. Next easiest thing to try is replacing plugs.
Safety Car
Joined: Apr 2006
Posts: 4,057
Likes: 421
From: BC
I use the R45XLS gapped at .035 on my 69 427/390. I chased a slight miss that only occurred after warm up and light throttle forever. It turned out to be the connector inside the plug boot at one plug wire. It was not on the wire correctly and would arc cold then heat up and expand because of the arcing and then cause an intermittent miss. They were brand new stock type braided wires and the only way I found it was by using a timing light on each cylinder to check for constant/even spark. The wire was just slightly off, or out of the connector inside the boot and it was the last thing I suspected as that expensive set of braided wires was new.
There doesn't seem to be anything visual with those plugs you have that would cause a miss but plugs are cheap.
There doesn't seem to be anything visual with those plugs you have that would cause a miss but plugs are cheap.
Last edited by CanadaGrant; Apr 6, 2019 at 10:56 PM.
Thread Starter
Pro
Joined: May 2013
Posts: 570
Likes: 22
I use the R45XLS gapped at .035 on my 69 427/390. I chased a slight miss that only occurred after warm up and light throttle forever. It turned out to be the connector inside the plug boot at one plug wire. It was not on the wire correctly and would arc cold then heat up and expand because of the arcing and then cause an intermittent miss. They were brand new stock type braided wires and the only way I found it was by using a timing light on each cylinder to check for constant/even spark. The wire was just slightly off, or out of the connector inside the boot and it was the last thing I suspected as that expensive set of braided wires was new.
There doesn't seem to be anything visual with those plugs you have that would cause a miss but plugs are cheap.
There doesn't seem to be anything visual with those plugs you have that would cause a miss but plugs are cheap.
Safety Car
Joined: Apr 2006
Posts: 4,057
Likes: 421
From: BC
Sometimes the wire end will pull out of the crimp in the metal connector inside the boot just by removing it from the plug. The boot sticks, the wire doesn't and the connector stays with the plug boot while the wire slides back slightly. When I had this happen I thought it was a carb problem as it was only when warm and just on light throttle. Accelerator pump? APT adjustment? I didn't suspect the wires as they were new and had never even been removed yet but stuff happens...
Drifting
Joined: Aug 2013
Posts: 1,263
Likes: 512
From: perth Aus w.a
2020 Corvette of the Year Finalist (stock)
C3 of Year Winner (stock) 2019
I use the stock a c delco r44n plugs in my l68 found the r43n plugs to cold ,my wife thinks I am crazy because I have 31 sets of nos plugs .My answer was 'they don't go off '
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Thread Starter
Pro
Joined: May 2013
Posts: 570
Likes: 22
i checked the distributor and there is no play. I changed the plugs and made sure the wire connections were snug. Hopefully this corrects it.