Vintage J-13Ys or new AP85s ?

[GG-1]

Good morning C-friends!

The 1967 FSM specs J-13Ys as the best choice for spark plug replacement on my 383HP, which can still be had NOS onlne. I see many here with Chrysler big blocks running new Autolite AP85s as the comparable contemporary choice. Does it really matter?

Thanks, Alex

 

[Yatzee]

Good morning C-friends!

The 1967 FSM specs J-13Ys as the best choice for spark plug replacement on my 383HP, which can still be had NOS onlne. I see many here with Chrysler big blocks running new Autolite AP85s as the comparable contemporary choice. Does it really matter?

Thanks, Alex

Yes it does! I actually run iridium plugs in my engine for a couple of reasons. There is no gap change either when the engine is cold or hot and there's less surface for carbon to build up on as far as the electrode goes. You can literally throw the whole "heat range" thing out the window with these type of plugs as they have low heat retention for quenching. They're a bit pricey but mine have been in for a lot of miles with no signs of fowling or distortion of the electrode. They truly are a serious improvement from conventional style plugs.

 

[Ripinator]

Good morning C-friends!

The 1967 FSM specs J-13Ys as the best choice for spark plug replacement on my 383HP, which can still be had NOS onlne. I see many here with Chrysler big blocks running new Autolite AP85s as the comparable contemporary choice. Does it really matter?

Thanks, Alex

I know that Champion and Autolite both have their fans, but in my opinion, the Autolite (regardless of whether or not its platinum) is a superior plug. Years ago, I had a friend who used to drag race a '63 Dodge super stocker with the 426 High Perf engine with 13.5:1 compression, staggered Carter four barrel carbs, aluminum front end, etc. He replaced his Autolites (with fifteen runs on them) with some new Champion plugs furnished to him by a Champion factory rep. After the second run with them, the engine began to miss. He pulled them and re-installed his old Autolites. The miss went away. I've run Autolites ever since.

 

[GG-1]

Thank you.. Quite the endorsements!

 

[CBODY67]

Actually, Chrysler spec'd between J-10Y for the 4bbl HP motors to J-14Y for the 383 2-bbls. Many were J-12Ys, too. From my experiences, you'll find that some of the other brands will kind of blend the Champion heat ranges together, covering two of them with one plug.

I haven't used Autolites, but I have used Motorcraft plugs and they hold up well, even the standard ones. Spend the money for the Iridiums if you drive a lot, but the plugs on the '67 are better to service than the '70s and such. I've used the NGK V-Power plug and like its gap style, but some of the same orientations can be had other ways, too. PM me for details.

I'd aim for a J-12Y plug in the other brands, then gap them closer to .040" than .035"(but not .040" unless you have an electronic ignition), and add about 2.5 degrees BTDC to the initial timing and see how it goes. NO need to use NOS plugs when new ones are available from normal vendors!

CBODY67

 

[GG-1]

Actually, Chrysler spec'd between J-10Y for the 4bbl HP motors to J-14Y for the 383 2-bbls. Many were J-12Ys, too. From my experiences, you'll find that some of the other brands will kind of blend the Champion heat ranges together, covering two of them with one plug.

I haven't used Autolites, but I have used Motorcraft plugs and they hold up well, even the standard ones. Spend the money for the Iridiums if you drive a lot, but the plugs on the '67 are better to service than the '70s and such. I've used the NGK V-Power plug and like its gap style, but some of the same orientations can be had other ways, too. PM me for details.

I'd aim for a J-12Y plug in the other brands, then gap them closer to .040" than .035"(but not .040" unless you have an electronic ignition), and add about 2.5 degrees BTDC to the initial timing and see how it goes. NO need to use NOS plugs when new ones are available from normal vendors!

CBODY67

Thanks for the info.
My 67 FSM specs are for Champion J-13Y for 383 4bbl HP, J-12Y if need be.
All that said, I just put basic copper core Autolite 85s in yesterday and gapped them at .035, now wonder if I should pull & re-gap at .037 based on your suggestion. We'll see how she runs after adjusting new points, and getting into all tuning/timing.

 

[Polara_500]

For .002 difference, nowhere near worth the required effort.

 

[Ripinator]

Thanks for the info.
My 67 FSM specs are for Champion J-13Y for 383 4bbl HP, J-12Y if need be.
All that said, I just put basic copper core Autolite 85s in yesterday and gapped them at .035, now wonder if I should pull & re-gap at .037 based on your suggestion. We'll see how she runs after adjusting new points, and getting into all tuning/timing.

After another 80K miles, you might wanna do that - but with an upgrade to a new set of AP85 Autolites. For now you are good to go.