Help Choose new Plugs for worked 360

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392Mopar

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Hey guys, I want to change out the plugs in my 72 Duster and what some opinions on whats the best choice. Heres my specs...

72 Duster 360, 4 speed, 8 3/4 with 3:91's

360 .030 over 10:1 compression
mildly ported J Heads 2.02/1.60
Racer Brown SSH-25 Hydraulic cam (238 duration @ .050 and .485 lift on intake/exhaust with a 108 Lobe separation)
Holley Strip Dominator single plane intake
Quick Fuel 750 DP
Mopar Performance distributer with Crane High 6 Digital Ignition
Timing is 18 at idle and 34 total

Car is quick but lacks a little on the low end, want to switch out the cam and put on a Performer RPM Air Gap once I get some $ together. But for now just tuning her up. What do you guys think for plugs for this motor, its running Champions now, forget the # offhand.

Butch
 

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I would first try bumping your initial timing up to around 26 or so and limit the total advance to around 38. Youmight be surprised. I know I was and mine is even higher.
 
In my own personal oppinion you just can't go wrong with NGK and I have solved quite a few minor running problems just by changing to them. (on all kinds of engines from auto to motorcycles and cars of varied designs.)
The V power series seems like they are a little over hyped, but they are still NGK so it sure can't be a negative to anything.
 
Really? I'll have to give that a try, worth a shot. Thanks!

Also I just looked in my notes and right now I'm running a Champion RC12YC , just stick with those or try something else?

Butch
 
TrailBeast said:
In my own personal oppinion you just can't go wrong with NGK and I have solved quite a few minor running problems just by changing to them. (on all kinds of engines from auto to motorcycles and cars of varied designs.)
The V power series seems like they are a little over hyped, but they are still NGK so it sure can't be a negative to anything.
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Any idea on what part #'s on the NGKs for a worked 360?
 
I would run whatever plugs the heads require. Whatever year they are, just buy plugs to fit them. Sounds like that's what you've done.

I agree about more initial timing. That's the number one consistent thing I see here is people try to time these like chevys.
 
I had bad luck with champions. I run cold Ngk plugs but can't remember the part number and I have aluminum heads so it's probably different anyways.

I was told to run as cold of a plug as possible.
 
I run NGK 5155 in my bored and stroked 360 (408). My compression is 12:1 and I gap them at .050. I run NGK in almost every vehicle we get in the shop. I never have issues with them. I just changed mine a few weeks ago. They looked good but were two years old with 16,000 hard driven, race gas fueled miles.
 
Mo-Par said:
I have always had the best luck with Autolite plugs in any brand engine.
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I used to use autolites also (7 or so years ago), but when I switched to the same heat ranged ngk, it was a noticeable improvement. Since then, I switched everything I own over to ngks and would never consider moving back.
 
If I wanted another brand I would just cross whatever Champion number was correct and go with the stock plug in another brand.

Those of you going to colder plugs are makin a mistake. Colder than stock heat ranges were for engines with high compression and even then were only a couple of steps colder. They were also used in much better fuel without ethanol and with lead to help with spark knock resistance. I wouldn't use anything except the stock plug for whatever year the heads are.

Of course aftermarket heads are a different story. You should use whatever the manufacturer suggests. Even then it's somewhat of a crap shoot, because even they won't know your combination so you may need to swap around until you get the best results.

All in all, people make too big a deal when choosing plugs. Pick one that fits and is the right plug in the book. Done deal.
 
ir3333 said:
..i've used most brands and have never noticed a difference?
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Me either. But I have had the most success with the one plug I see people degrade on a regular basis. Champion. Yall should keep this in mind. Ain't but like three companies in the world that actually MAKE plugs. So that means chances are the plug you are running was made by another company that you don't like.
 
RustyRatRod said:
Me either. But I have had the most success with the one plug I see people degrade on a regular basis. Champion. Yall should keep this in mind. Ain't but like three companies in the world that actually MAKE plugs. So that means chances are the plug you are running was made by another company that you don't like.
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wow kinda like lifters...enlightening...
 
Is your vacuum advance hooked up to ported vacuum or manifold vacuum? Disconnect it temporarily, put a vacuum gauge on your manifold with a long enough tube to have it inside the car for later testing. Keep advancing your timing until your vacuum quits getting higher. That's your initial timing. Weld up the slots and use a chain saw file and a timing light to limit your total timing to 34 or 36 whichever it likes better. Make sure your centrifugal advance is all in at your highway cruising speed 55, 60 or even 65 etc.

Make sure you don't get too much vacuum advance. You may have to weld up the stop and file it to get it dialed in. Re connect it it to manifold vacuum only, then make sure you have 50 to 52 total cruising down the highway 55-60 at barley any throttle.

The vacuum advance should drop to zero as soon as you punch it or take of with significant throttle helping avoid gas knock. Adjust your total mechanical timing lower if you are gas knocking at all.

This will improve your off idle drivability dramatically and give you better mileage on the highway and around town.
 
bad440 said:
wow kinda like lifters...enlightening...
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Exactly. Most lifters are made by Morel. I would say probably 90% of them. Mike from MRL could probably give you a more accurate number.
 
Ok guys great info here, Thanks. So I decided to go with a set of Autolite 3923 plugs gapped at .045 which are equivalent to a Champion RC9YC and a couple steps cooler then the RC12YC's I was running. Went with the Autolites because they are cheap ($1.99 each), if the cooler range works out good I'll by a better set like NGK's. I also found 2 wires boots fried from the headers even though they had heat boots on them, they were 8.8 Moroso Race wires. So I swapped them out to a set of 8mm Accels I had from another motor, I'll have to order a new set with some angled boots for cylinders 5 and 7. I also bumped timing to 24 initial and 34 total with vacuum disconnected, then reconnected to ported.
Took it for a cruise and it made a big difference, I'm sure my 2 burnt wires were the cause of my rougher than usual running. But even compared to before, smoother running, more responsive, and seems to have more torque and power. So I'm gonna bump it up a little more to 26/36 and go from there, then check my plugs to see how there looking.

Now for the ported vs manifold vacuum debate. If you hook to manifold wont that instantly boost you initial timing way up? Always thought ported was the way to run them.

Butch
 
Hope this helps on tracking down NGK plugs and heat range. Higher number the colder the plug.

NHK's HR. Item no.
r5671-7 4091
r5671-8 4554
r5671-9 5238
r5671-10 5820
r5671-11 6596
 
392Mopar said:
Ok guys great info here, Thanks. So I decided to go with a set of Autolite 3923 plugs gapped at .045 which are equivalent to a Champion RC9YC and a couple steps cooler then the RC12YC's I was running. Went with the Autolites because they are cheap ($1.99 each), if the cooler range works out good I'll by a better set like NGK's. I also found 2 wires boots fried from the headers even though they had heat boots on them, they were 8.8 Moroso Race wires. So I swapped them out to a set of 8mm Accels I had from another motor, I'll have to order a new set with some angled boots for cylinders 5 and 7. I also bumped timing to 24 initial and 34 total with vacuum disconnected, then reconnected to ported.
Took it for a cruise and it made a big difference, I'm sure my 2 burnt wires were the cause of my rougher than usual running. But even compared to before, smoother running, more responsive, and seems to have more torque and power. So I'm gonna bump it up a little more to 26/36 and go from there, then check my plugs to see how there looking.

Now for the ported vs manifold vacuum debate. If you hook to manifold wont that instantly boost you initial timing way up? Always thought ported was the way to run them.

Butch
Click to expand...

Thanks for the update and glad you saw some improvements!
:burnout:
 
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