Stick with autolite 63's or go to 65's?????????????

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duster360

duster360

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I have been running autolite 63 plugs in my 340 for a while now. They do fine, but I have been noticing that others here have been running the autolite 65. I know the 65 is a hotter plug. Should I consider running this plug? The reason I run the autolite 63 is because it is the same heat range as the factory champion RN9YC plugs that came in my engine and now I can't get through my local parts store without special ordering them. I realize that was back in the day when the engine had a points distributor and ran 100 octane gas. The engine now has MSD 6AL ignition and MSD coil. I run 93 octane fuel. Would the 65's be a better choice for my setup or should I just leave it alone and stick with the 63's?
 
well the autolite 65 is the stock plug for a street hemi...

what is your build? unless your running high compression, high rpm, then you probably dont need a plug that cold...

i would do a 64 or 65...
 
The engine is a 1970 340 with the factory 10.5:1 pistons. I know the compression isn't that high because I am using the felpro .039" gaskets vs. the factory .025" steel gaskets. I do know the compression is still high enough that the engine will absolutly not run on low octane fuel. I accidentally shot some 87 octane in it (all my other newer vehicles run 87, habbit I guess ) and it rattled like crazy on the way home and kept running after I tried to shut it off. IT really liked the 100 octane I used to be able to get from the pump.
 
Since I am running the MSD now, should I open the gap up on my plugs or stay with the stock .035" gap?
 
duster360 said:
The engine is a 1970 340 with the factory 10.5:1 pistons. I know the compression isn't that high because I am using the felpro .039" gaskets vs. the factory .025" steel gaskets. I do know the compression is still high enough that the engine will absolutly not run on low octane fuel. I accidentally shot some 87 octane in it (all my other newer vehicles run 87, habbit I guess ) and it rattled like crazy on the way home and kept running after I tried to shut it off. IT really liked the 100 octane I used to be able to get from the pump.
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i hear ya... when i throw the 100 leaded in my dart it runs and smells SO much better!!

but yea 64 or 65 will be better...

duster360 said:
Since I am running the MSD now, should I open the gap up on my plugs or stay with the stock .035" gap?
Click to expand...

i think under 11:1 your able to go up to .050" gap... i havn't been able to test different gaps yet at the track so im still at .037
 
Sorry, ran Autolites in my HP 273 and it ran like crap. Compression seems to make a difference with the heat range. Lower compression, hotter plug. tmm
 
I used to run the champions until it became an act of congress to get them through my local parts dealers.
 
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