Looking for advice on spark plug selection
Thread Starter
Burning Brakes
Joined: Oct 2000
Posts: 877
Likes: 59
From: Minneapolis, MN USA
Looking for advice on spark plug selection
OK, with many thanks to all of U, my car is up and running. Now I am working on tuning it up a bit, etc…need to change the plugs and would like Ur opinion on what to use.
I have a 1970, 350hp/350 engine, double-pumper Holley carb (I’m told it’s way over carbureted…the previous owner raced it), Edelbrock intake, exhaust headers, standard coil/cap/rotor/points, it also has a different cam (but I know nothing about it…again, previous owner’s work).
The options I’m considering are –
AC Delco R44S – this is what the previous owner has in the car now
Autolite R84 – the previous owner used these plugs in the past
AC Delco R43S – the guys at NAPA recommended these for me
AC Delco Rapid Fire #2 – I’ve seen many of U here are using these
Champion somethings - this was being considered...but dropping out of the race
I don’t race the car or anything…but it’s always nice knowing you have the power if U want it - U know how it is! I guess I’m not sure if I will notice the difference going with the Rapid Fires or not? The guys at NAPA didn’t think I would? I would appreciate any recommendations from this group!!
I have a 1970, 350hp/350 engine, double-pumper Holley carb (I’m told it’s way over carbureted…the previous owner raced it), Edelbrock intake, exhaust headers, standard coil/cap/rotor/points, it also has a different cam (but I know nothing about it…again, previous owner’s work).
The options I’m considering are –
AC Delco R44S – this is what the previous owner has in the car now
Autolite R84 – the previous owner used these plugs in the past
AC Delco R43S – the guys at NAPA recommended these for me
AC Delco Rapid Fire #2 – I’ve seen many of U here are using these
Champion somethings - this was being considered...but dropping out of the race
I don’t race the car or anything…but it’s always nice knowing you have the power if U want it - U know how it is! I guess I’m not sure if I will notice the difference going with the Rapid Fires or not? The guys at NAPA didn’t think I would? I would appreciate any recommendations from this group!!
Team Owner
Joined: Jul 2004
Posts: 23,957
Likes: 174
From: South West - but north of Dayton, Ohio
I like the Bosch Platinums - been running them for over a year and haven't had the first issue. I run a hot coil and have them gapped an additional .010 for hotter spark.
74 L-82 Modified
74 L-82 Modified
Safety Car
Joined: Aug 2000
Posts: 3,943
Likes: 44
From: Florham Park NJ Port Credit Ontario
Originally Posted by gkull
When I had tapered peanut plug heads the best I found was Bosch P+4
The 4 tip makes it so you don't have to index the plugs.
The 4 tip makes it so you don't have to index the plugs.
Tech Contributor
Joined: Aug 1999
Posts: 14,373
Likes: 6,371
From: At my Bar drinking and wrenching in Lafayette Colorado
Stewart -
Indexing the plugs is when you make all the plugs align their electrodes in the same "clocking" relative to the combusion chamber. Idea is to get the "open" spark front of the electrode facing the chamber for improved and uniform flame front travel. There is some discussion whether or not this is actually effective in a street driven car... Plugs that do not use the conventional "J"-shaped negative electrode cannot be indexed.
By the way, I use standard Autolite resistor plugs. They are very easy to "read" when tuning and working on the car, whereas the platinum plugs burn so clean that they can "mask" problems that need to be corrected. I'm sure the platinum plugs have longer life, but I like the "readability" of the Autolite standard plugs, and there is no difference in power output with either plug.
Indexing the plugs is when you make all the plugs align their electrodes in the same "clocking" relative to the combusion chamber. Idea is to get the "open" spark front of the electrode facing the chamber for improved and uniform flame front travel. There is some discussion whether or not this is actually effective in a street driven car... Plugs that do not use the conventional "J"-shaped negative electrode cannot be indexed.
By the way, I use standard Autolite resistor plugs. They are very easy to "read" when tuning and working on the car, whereas the platinum plugs burn so clean that they can "mask" problems that need to be corrected. I'm sure the platinum plugs have longer life, but I like the "readability" of the Autolite standard plugs, and there is no difference in power output with either plug.
Safety Car
Joined: Mar 2000
Posts: 3,541
Likes: 448
From: Central Pennsylvania
Originally Posted by lars
They are very easy to "read" when tuning and working on the car, whereas the platinum plugs burn so clean that they can "mask" problems that need to be corrected. I'm sure the platinum plugs have longer life, but I like the "readability" of the Autolite standard plugs, and there is no difference in power output with either plug.
Platinums aren't the best choice for the older ignition systems. They're just not "hot" enough to justify platinums. They might have a tendency to foul quicker, as they don't accept any type of oil or fuel well, especially without the juice popping thru them to burn the stuff off.
Standard Bosch plugs for me. Work great. Never an issue.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
2027 Corvette vs The World: Every C8 vs Its Closest Competitor
Joe Kucinski
Melting Slicks
Joined: May 2004
Posts: 2,084
Likes: 1
From: Aussie expat in Saudi Arabia
I dunno if you can get them in the US, but I used to run Golden Lodge spark plugs in my race car. Can't remember if they were platinum or what, but they had 4 negative electrodes on each plug - good spark and they never seemed to foul...
Instructor
Joined: Mar 2004
Posts: 188
Likes: 0
From: La porte Texas
Lars is right (as usual) Also on my race motors , with the dome height required for 15 - 16 to 1 ratios, if indexed wrong the piston has actually kissed the ground electrode closing it up leaving a dead hole. I have gone through as many as 100 new plugs just to get a couple of useable sets.
