1966 Monaco 4 BBl conversion ( Camshaft ?)

[Gerald Morris]

Wich model of NGK?
I can't find any cross reference chart to translate my Champion RJ14YC to a iridium spark plug

7355. Rock Auto carries them for $6.11/ea. You use the same Champion I do, so the NGK 7355 should work for you. When I get a little more $$ God-willing, later this summer, I plan to do my annual spark plug replacement w them. THEN I'll see how long they last. I'll even gap them out to .038" for the better spark. My Champions weren't in too bad a state either, so I'll likely hit them w a wire brush and a little solvent, and use them on the 400 I copped and will be a-building, as backup for my 383.

More Information for NGK 7355

 

[Ripinator]

Wich iridium spark plugs can you recommend for a mild street 383?

Iridium schmeridium. . . Throw a set of Autolite AP85s in it and fergit it.

Autolite - Online Parts Lookup

 

[Turboomni]

Everyone hates Champion I take it.

 

[Polara_500]

I never had any problems with Champion but recently no longer carried in town so I have to make do...

 

[Turboomni]

I have used Champions too in the past with no problems. But most people I know say "Champions SUCK!!!" and I don't know why.

 

[70bigblockdodge]

I've had problems with champions years ago but may have just been a thing. I've had good luck with all brands. I would not waste the $ on Platinum, iridium, etc those are for longevity like 100,000 mi before you change plugs, if you are doing that with a classic car you need to have the car taken off of you and go buy something new.
To OP put a Mopar Performance Magnum resto cam, however for some reason the price has gone through the roof which leads me to believe either the manufacturer changed or FCA is just sticking it to us, both make me shy away.
A substitute is comp cams has a similar profile. The one you listed is okay, I would choose something in that neighborhood but a split pattern with more exhaust duration to deal with the exhaust manifolds you most likely have but it will not make a terrible difference.

 

[CBODY67]

The Champion J14Y is the OEM spec plug for a whole bunch of 383 2bbls over the years. What you have is the resistor ("R") Copper Plus ("C") version.

The RockAuto listings shows NGK 7355 (which should be the number for individual plugs, as NGK might also sell them in boxes of 4, with a different part number -same plug- for that quantity. The individual plug for this number XR5IX. Their listings show the XR5IX (RJ12YC)and XR4IX (Champion RJ14YC). NGK heat range numbers are the reverse of other plugs, higher heat range number=colder.

I've run the XR5 V-Power plug in my '67 Newport 383-4 (906 heads) with no problems. So that heat range will work for a decently good motor, I suspect.

If the Champions are working well now, whether in the J14Y or J12Y variations, the only other spark plug brand I've found that might be better is Motorcraft (in normal plugs). The NGK V-Power plug is interesting, though. That's another story. Just depends upon how much money you want to spend and how many times. RockAuto lists the normal plugs at about $1.50 each, thereabouts, with the NGK Iridiums at about $6.50each. Whereas the normal plugs would need to be looked at about every 30K miles, the Iridiums are more like 100K+ miles. First, there were Platinums (50K-100K before needing replacement. Those who used platinums in OEM are now almost all using Iridiums now, OEM production.

I know the underhood of the '66 C-body cars is generally good for easy spark plug changes anyway (#7 is better with the gravel shield removed from the bottom of the steering column), so changing plugs is not as much or a deal as the '69-'73 cars, or some B/RB B-body cars (some plugs from underneath!). So it's your choice of how much money (less) and time (more) taking care of plugs every so often. To me, the harder the plugs are go get at, the less you want to do them, so get the longest-lasting plug you can buy and afford for those vehicles.

FWIW, the NGKs are supposed to take a little less "juice" to fire than other brands. I saw that somewhere about 15 years ago. The V-Power plug was used OEM by Toyota as they'll fire leaner mixtures than a non V-Power plug. The Denso U-Groove plugs don't seen to work as well. SplitFires? I spent the $50 for a set of them in my '80 Newport 360. Poor durability and no additional performance or mpg. I chunked them and went back to NGKs. In magazine performance tests, they appeared to work. NOT in my car, though.

CBODY67

 

[CBODY67]

I never had any issues with Champions in our '66 or '72 Newports (J14Y/J13Y, respectively). They always burned well and lasted good. I used then I'm my '70 Monaco "N", too. No issues. I ended up with a stash of used Champions that worked well instead of the "specific" lawn mower spark plugs in my Briggs&Stratton lawn mower engines. Just filed and gapped them.

I ventured off into Motorcrafts on our '69 Chevy pickup. I got a Magic Santa Gift Certificate to the local Ford dealer and the only thing I could think of that I could use from them was spark plugs. At the time, I was using the OEM spec ACs in it. I did the research for the heat range and they had some. I'd usually pull the ACs out for a check and re-gap every couple of months I put the Motorcrafts in and remember to check them 6 months later. They were fine so I put them back in. I used them in my '77 Camaro, later discovering that my new friends with similar cars had changed form AC to Motorcraft in their Chevy motors long ago. Similar reasons of durability.

I found a NGK fold-out at a Toyota dealer that detailed what was the V-power NGK. I had a friend in the auto supply business so I went up there and got into his NGK catalog after work. There was a direct cross for the N14Y plugs in the '80 Newport 360, so I had him get some for me. The car had Motorcrafts in it when I got it and they were all burning nicely. The car ran as expected. The first time I fired it with the NGK V-power plugs, I could tell it was better. Throttle response was crisper, idle quality was better, and it sounded better. No noticeable power increases, but throttle response was better off idle. From experiences in other engines, the open chamber of the A-block combustion chamber (less active air flow?) needs these plugs. The other more wedge-shaped chambers on my '67 383 and other GM motors, improved throttle response, especially on a cold engine that's a little lean on the choke, but not quite the same amount of improvement as on the A-block engine.

The ACDelco Rapidfire has all of the electrode "tricks" for the best exposure of the flame kernel to the mixture in the combustion chamber. The shorter ground electrode (J-gap Champion race plugs from the 1960s), tapered to a blunt point. But no platinum or other stuff. You can do the same things with a point file and time on a Sunday afternoon, if you are so oriented. Or, you can use a pair of pliers to rotate the ground electrode so that it only covers 1/2 of the center electrode, with the correct gap measurement, rather than using a point file and shortening it that way (or with a diagonal cutters, then dressing it with a point file). DIY or buy them "ready made".

Enjoy!
CBODY67