Author Topic: Spark plugs in a 383  (Read 1061 times)

Offline Cdnchallenger

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Spark plugs in a 383
« on: October 24, 2011 - 06:08:17 PM »
I just picked up a 70 challenger with a 383 that does not run. The car came with both long and short plugs installed. Which is correct or does it depend on heads or pistons etc? :cheers:




Offline Chryco Psycho

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Re: Spark plugs in a 383
« Reply #1 on: October 24, 2011 - 06:53:57 PM »
the correct plug is RJ12YC from Champion ,that or the Autolite will make the best power .
The J plugs are short thread , N plugs are long thread , the  N plug was used in the small blocks , Hemis & Slant , the B & RB engines use short J plugs

Challenger - You`ll wish You Hadn`t

Offline Cdnchallenger

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Re: Spark plugs in a 383
« Reply #2 on: October 24, 2011 - 07:11:09 PM »
We are trying to get this engine running. Plugs seem to be constantly soaked in gas so i was worried that I was not getting a good spark . Put longer plugs in and seems to run better. Any thoughts? One good thing that this car has is great compression in all cylinders.

Offline 'Cuda Hunter

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Re: Spark plugs in a 383
« Reply #3 on: October 24, 2011 - 08:21:18 PM »
Are the plugs still wet?

If your plugs are wet your carb is dumping too much gas. 
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Offline Road_Runner

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Re: Spark plugs in a 383
« Reply #4 on: October 24, 2011 - 08:43:56 PM »
I've run J11Y's for years in my 383, believe that's what came on the HP 383 motors in 70, but the J12Y's are the current plug since J11Y's aren't made anymore.  Either way J is the right series plug and the number is the heat range.

Later, Jim
1970 383 Roadrunner Tor Red
1973 318 Barracuda Mist Green
2014 Mustang GT/CS Convertible All Black