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I have a set of autolite AP 404 spark plugs that were given to me by the previous owner of my 69 427 390hp. Has any one used these plugs? Would like to know if they are worth keeping for the next tune up
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Send PMFrederick, MD - USA
Joined: 9/8/2003
Posts: 3398
Vette(s): 1969 convertible L71 427/435 4-speed black interior
I have AC spark plugs in my 427 but realistically, as long as the plug you use is of the right heat range for the application, it really shouldn't matter. I know many have their own favorites for spark plugs, the fact remains they are all designed to do the same job.
Unless your car has modifications such as cylinder head work, cam changes, etc., whatever meets factory specs is fine. There's no need to use exotic (read that as expensive) spark plug designs with a stock ignition system. You'll only make the parts manufacturer richer and see no gain in performance.
As I said, if the Autolite spark plugs are the correct application and heat range, there's no reason not to use them. Getting them for free is a bonus.
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Former Member
Send PMManteca, CA - USA
Joined: 11/20/2005
Posts: 3623
Vette(s): 1978,two tone,Metalic Rootbeer & gold
1975 L48 4 speed
Them's my senaments azackly 
.
.Jimmy B.
Just can't wait to get on the road again. 
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7
I agree that w/ our vintage engines, the right heat range is the most important feature but when the mfgs went to EFI, I found that I got the best results w/ the OEM recommended plugs.
For instance, I found that my engine ran best w/ one heat range hotter and w/ a projected tip.
For instance, I found that my engine ran best w/ one heat range hotter and w/ a projected tip.
1973 L-82 4 spd
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I am in the process of getting a tune up and my mechanic will only use ac delco plugs. He is installing the rapidfire # 4. The autolites did not cost me anything, so I will keep them for a late time.
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in Forum: C3 Engines, Driveline and Handling
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