[C1] Extended Plugs
Thread Starter
Instructor
Joined: Mar 2021
Posts: 151
Likes: 50
From: Florida
Extended Plugs
Dumbest question of the week… here goes:
I have Autolite 295s plugs in my 1958 283 cubic in with dual carters. I would like to try a slightly hotter plug as they foul out within a few hundred miles. Carbs run great and already set lean.
I read numerous threads and like the idea of trying AC45S plugs as they are ‘extended’ and might help with my low rpm and lots of idle driving.
The engine was rebuilt before I bought the car.
Is there danger of hurting the valves or pistons trying an ‘s’ extended plug? Is there a way to measure and make sure?
thanks all.
I have Autolite 295s plugs in my 1958 283 cubic in with dual carters. I would like to try a slightly hotter plug as they foul out within a few hundred miles. Carbs run great and already set lean.
I read numerous threads and like the idea of trying AC45S plugs as they are ‘extended’ and might help with my low rpm and lots of idle driving.
The engine was rebuilt before I bought the car.
Is there danger of hurting the valves or pistons trying an ‘s’ extended plug? Is there a way to measure and make sure?
thanks all.
Melting Slicks
Joined: Jun 2017
Posts: 2,267
Likes: 1,769
From: Central Michigan
2023 C1 of the Year Finalist - Modified
I had/have the same issue. I'm using the hottest extended I can find (can't remember what brand or number) but they run black. Haven't fouled yet but I think the issue is that the heads run so much cooler (180 degrees) and possibly with some combination of gasahol. If you find anything let me know.
Racer
Joined: Sep 2020
Posts: 388
Likes: 135
From: New Berlin
According to a "Ford Shop Tips", circa 1960's, an extended tip gives a small advance (effectively) without any ignition advance. This is with the same heat range. Keeping the heat range the same whist extending the nose looks like you've got some limitations. I buy the idea, but it does seem some combustion chambers won't have much room - of course it isn't much of a length change. I'm more worried about production differences from original, as our Jaguar head had exposed threads with some supposedly appropriate plugs (obviously I had the head off and was checking this as I thought I'd clock the plugs. I know this is thought to be stupid, but the Jag is a hemi, with odd plug placement and I insist it is a good idea in some rare designs.
Le Mans Master
Joined: Nov 2015
Posts: 7,463
Likes: 2,643
From: Really Central IL Illinois
I run R45S or equivalent in all of my SBs and they are just fine. I had a picture on a prior post where I installed a plug in a head and stroked the valves over 1/2" and there was no clearance issues. I have also ran them with 12.5 to 1 popups, but always indexed them for racing purposes.
