Spark Plugs in a modified 258?

Spark Plugs in a modified 258?


Broadalbin, New York
1979 CJ7 Rebuild Project, 258 Aluminum Intake, 4 bbl Holley, Split Headers, Dual Exaust, T-150.
Having trouble figuring out what plug to use in my 1979 CJ7 I just bought. It calls for Autolite 985 but I pulled out a Splitfire SF426E that is about a 1/4" shorter than the AP 985. The motor has an aluminum intake and a 4bbl Holley with split dual exaust. Anybody got any ideas on this one?
I would go for the 985s, then check the deposits on the spark plugs, and adjust the carb jets until a good air/fuel mixture shows on the plugs. That Holley four holer is a bit on the big side in my opinion.
Thanks Torxhead, I think I will do that. Yes! I think that the 4 holer is a bit much too! I just bought it last month and it's a project jeep so that set up will probably change down the road! Thanks again!
I've used the 985's for years in my heavily modified 4.2 as well as my 401 without any issues. I've never had any desire to use the splitfires or the platinums or any other snake oil plugs. The key is proper gapping, timing, and fuel mixture for the application...
Thanks CJim7! I did put the 985's in and gapped them at .35. After the plug install I notice it's running like on high idol now? I'm trying to find someone local who can come take a look at the Holley and check the timing. This jeep has been sitting for quite some time before I bought it.

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