What brand of spark plug and model # to use on a stock 383?

[hewi]

383 owners - What do you guys use/recommend?

Cheers,
Bruce

[deputycrawford]

I have used AC   R45S plugs for years. I have switched to Champion RJ 12YC and they aren't too bad. I am looking for a set of NGK's for my next set but don't know the numbers. I went to Champion because they had the plugs two stages colder. I heard NGK and Autolite have good plugs. I guess you could start with the factory plug choice of Champion and go from there.

[firefighter3931]

I have used NGK XR5's on many BB engines with very good results. Good plug for iron headed street motors running up to 10.5:1 compression. The heat range is bang on for pump gas builds. 


Ron

[Chryco Psycho]

Champ RJ12YC

[is_it_EVER_done?]

383 owners - What do you guys use/recommend?

I was lucky enough to buy out a dealerships inventory of Mopar branded Champion J11Y plugs many years ago, so I can't offer any help on what brand or heat range works best out of the available plugs now days, but keep in mind that most the plug manufacturers recommendations have no basis in reality since they will only recommend plugs that still exist, even if they are too hot.

An example is Champion. The stock plugs were J11Y's in the performance big blocks, and frequently a J10Y was a better choice for racing or after header installation, but when the 10's and 11's were no longer made, "miraculously" the J12Y became the proper plug. The fact that it is too hot is simply overlooked and the recommendation and cross-reference charts were rewritten. The same goes for the other manufacturers, some of which combined four heat ranges into a single plug.

Fortunately it's not hard to work around these hotter plugs by slightly richening the fuel mixture and/or reducing the speed of the timing advance, or dropping the operating temperature down, and most people aren't even aware that this is something that is being worked around since the proper plugs haven't been available for about 20 years now, but if fuel mileage is of any concern to you, it might be worth your while to try the coldest available plug from a few different brands to see if any come close to stock and tune your engine to them. A stock Road Runner was an exceptional performer, but would also get 17 MPG or better if you weren't hot roding it. The same car will lose performance and mileage when tuned to a hot plug.

[histoy]

Autolite #86 should work well