Spark plugs for AFR's
Thread Starter
Safety Car
Joined: Dec 2007
Posts: 3,616
Likes: 5
From: Sandhills of North Carolina
Spark plugs for AFR's
I'm trying to figure out which plug will be the best for me to run. AFR says no tapered plugs (14mm x 3/4" gasket) so I guess that is the old type with the washer on them. Most of the Plug numbers they recommend do not come up on Summits site. A couple do an AC 41629 resistor a NGK 7405 non resistor. I have no idea what heat range I should run.
My car is basically a street car but I do take it to the drag strip on occasion.
I'm open for suggestions. Should I just contact AFR on this?
My car is basically a street car but I do take it to the drag strip on occasion.
I'm open for suggestions. Should I just contact AFR on this?
Melting Slicks
Joined: May 2001
Posts: 3,014
Likes: 18
From: Raleigh, NC
If you look at the directions for the heads (either the paper copy or the .PDF on the AFR website) they list a variety of brands and part numbers. The part numbers they list will work for any auto parts store. You shouldn't have to order the plugs from Summit/Jegs, a local auto parts store can hook you up.
Thread Starter
Safety Car
Joined: Dec 2007
Posts: 3,616
Likes: 5
From: Sandhills of North Carolina
If you look at the directions for the heads (either the paper copy or the .PDF on the AFR website) they list a variety of brands and part numbers. The part numbers they list will work for any auto parts store. You shouldn't have to order the plugs from Summit/Jegs, a local auto parts store can hook you up.
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Race Director
Joined: Nov 2003
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From: Overland Park Kansas
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What's a tapered plug? I thought they all had metal washer's built-on them. I was just going to pick one of the x-ref numbers at a local store too. In fact, I was leaning to the Bosch Platinum 2's. Plugs aren't the quickest job in the world, so why not go platinum and let them be for several years?
Melting Slicks
Joined: Mar 2002
Posts: 3,108
Likes: 126
From: S.L.C. UT
If you run a power adder, turbo, S.C., NOS, or high HP, I wouldn't run platinum plugs. They have too many issues with missfires when racing.
AFR doesn't recommend them either. They are good for a stock engine, but have their limitations.
AFR doesn't recommend them either. They are good for a stock engine, but have their limitations.
Race Director
Joined: Nov 2003
Posts: 12,221
Likes: 446
From: Overland Park Kansas
2020 Corvette of the Year Finalist (appearance mods)
C4 of Year Winner (appearance mods) 2019
I did have the RapidFires before the engine swap. Are they platinum? The price seems to indicate it. If not, why are they a $5 plug?
Is a tapered plug one with a tapered electrode (like the RapidFire)?
Is a tapered plug one with a tapered electrode (like the RapidFire)?
Melting Slicks
Joined: Mar 2002
Posts: 3,108
Likes: 126
From: S.L.C. UT
Rapid fires are Iridium, which I would still take a conventional plug for racing over that. It's kind of a PITA sometimes to change plugs, but for max performance sometimes there are compromises. About every turbo/blower/nos manufacturer recommends regular spark plugs.
I have used platinum or iridium plugs in performance engines, and sometimes you can get lucky. They don't missfire. But I have seen alot of problems when racing with platinum plugs... firsthand... and not just in my own car!
Tapered spark plugs just have a tapered end where it seals into the head, and the spark plug doesn't use a washer/gasket to seal to the head. AFR heads require spark plugs that use a small washer/gasket on the spark plug to seal against the head.
Edit: If I had to guess a hp number where I wouldn't run platinum plugs, it might be around 500hp. But STS turbo's doesn't like them in any of their kit's. And alot of their kit's are way below 500hp. And if you get a good set of platinum or iridium, they will work good for a long time. So it's kind of hard to exactly put a hp number exactly where you need conventional spark plugs. And there are people that have probably run more hp than this with platinum plugs.
I have used platinum or iridium plugs in performance engines, and sometimes you can get lucky. They don't missfire. But I have seen alot of problems when racing with platinum plugs... firsthand... and not just in my own car!
Tapered spark plugs just have a tapered end where it seals into the head, and the spark plug doesn't use a washer/gasket to seal to the head. AFR heads require spark plugs that use a small washer/gasket on the spark plug to seal against the head.
Edit: If I had to guess a hp number where I wouldn't run platinum plugs, it might be around 500hp. But STS turbo's doesn't like them in any of their kit's. And alot of their kit's are way below 500hp. And if you get a good set of platinum or iridium, they will work good for a long time. So it's kind of hard to exactly put a hp number exactly where you need conventional spark plugs. And there are people that have probably run more hp than this with platinum plugs.
Last edited by tpi 421 vette; Apr 27, 2010 at 02:36 AM.
