best plugs

[metcoll]

what  spark  plugs would be best for a 440 rpm heads

[c00nhunterjoe]

The exact part number will depend on your pistons and cam that are under the rpm heads. But ngk would be the main recommendation.

[metcoll]

would NGK XR5 be good...its got six pack replacement pistons

[justcruisin]

The recommended plug for the RPM head is an RC12YC Champion. However, as Joe said, it depends. In my opinion that plug is too hot, but depending on your compression could be OK. I would start with a colder plug and work from there. I like NGK.

[firefighter3931]

would NGK XR5 be good...its got six pack replacement pistons

The XR5's are good for factory iron heads. The RPM uses a 5/8 plug which is smaller. With that combo I would use the NGK......BCPR6ES and gap them @.040 


Ron

[justcruisin]

I agree, that is the plug I use on my 10.2:1 engine, the BCPR6ES-11 has a 0.043" gap.

[mopar0166]

I use the RC12YC Champion on my eddy rpm heads with little issues.   I also run an MSD ignition/6al box, that being said I usually gap them around .050.  Do you guys think that is too much gap, I believe I got that information from MSD, but I don't remember.  NGK is a good plug, but I have just always gone with the manufactures recommendation, my engine is 10:1 compression with sealed power pistons. 

Reason I ask, is I'm about to change the plugs which I do every spring.

[ODZKing]

I used champion for years and upon recommendation I tried the NGK plugs. They are fine and easier to get but I saw no significant difference in performance. Just my  2 cents.

[firefighter3931]

I use the RC12YC Champion on my eddy rpm heads with little issues.   I also run an MSD ignition/6al box, that being said I usually gap them around .050.  Do you guys think that is too much gap, I believe I got that information from MSD, but I don't remember.  NGK is a good plug, but I have just always gone with the manufactures recommendation, my engine is 10:1 compression with sealed power pistons. 

Reason I ask, is I'm about to change the plugs which I do every spring.

There's really no reason to gap a plug any wider than .040 inmo. That just places additional strain on the rest of the ignition components. I like the NGK's and have been using & recommending them for years. They just seem to work better and aren't as prone to fouling if the tuneup is "off" 

The BCPR6ES  is the correct heat range for a 10:1 aluminum headed motor. Hotter will risk detonation and cooler is more prone to fouling. Heat range is important and it makes a difference in how the engine behaves at low speed and idle. 


Ron

[ws23rt]

This is why I use NGK

[mopar0166]

Ron,

Thanks for the recommendation.  Ill have to dig up the msd info that apparently mislead me on the gap.  Id be willing to try the NGK, just wasn't in hurry to detour from edelbrocks recommendation.

[mopar0166]

I looked up the directions for MSD box and this is what I found, maybe this is what I'm referring to.

FROM MSD DIRECTIONS:

Spark Plugs: Choosing the correct spark plug design and heat range is important when trying to get
the best performance possible. Since there are so many engine combinations and manufacturers,
MSD does not recommend which plug or gap is exactly right for your application.
It is recommended to follow the engine builder or manufacturer's specification for spark plugs. With
that, you can then experiment with the plug gap to obtain the best performance. The gap of the plugs
can be opened in 0.005" increments, then tested until the best performance is obtained. MSD judges
the plug gap by compression and components.
These examples are just starting points to get you going
in the right direction. Every application is different and
should be tested and tuned.

Compression Spark Plug Gap
Up to 10.5:1: 0.050" - 0.060"
10.5:1 - 13.0:1: 0.040" - 0.050"
Above 13.0:1: 0.035" - 0.045"

[firefighter3931]

Yep, seen that recommendation from MSD many times....it's nothing more than a suggestion.  

The basic premise of electricity is that it will take the path of least resistance. So, increasing plug gap will strain components ; caps, rotors, wires, coils unnessarily. Why overtax those components when you don't really have to. The multi spark does a great job igniting the fire.

On a higher compression build or boosted application I can see tightening up the gap to compensate for increased cylinder pressure but for the typical street/strip pump gas combo a .040 gap is a good choice with an MSD box.


Ron

[justcruisin]

Like everything there will be lots of different opinions, here is my take based on my experience - the plug Ron recommended is the best choice for the majority of rpm headed street engines, the hotter plug which you have been using (and what edelbrock lists) may be fine, but there are lots of variables that dictate which heat range is best. Using a colder plug is safer, (plug inspections will tell you what the engine needs) in my own engine I could see small signs of detonation on the plug with the same plug you use, using a cooler plug solved the problem. I do run at sea level which can make a difference when you are on the edge of detonation.
As to the gap, the bigger the gap the harder it is for the ignition system to jump that gap, That means the coil must provide more voltage - harder on the coil, leads, cap, rotor and the controller. Larger gaps can promote a better burn but as compression goes up the gap needs to be smaller as it is harder to fire the plug. In a 10 - 10.5:1 e-headed street car I can't see the point in running excessive gaps, 0.040" is a good number to use, I use the BCPR6ES-11 which come with a 0.043" gap. I am sure MSD's recommendations are based on there testing, but as said, the larger gap does tax the ignition system more and a miss fire is more pron as time goes on.

[mopar0166]

Installed the NGK plugs, lowered gap.   did a test run.   engine seems to start easier and idle better.   I'm going on a trip from nj to md Thursday so we will see what happens.

thanks for the advice.

[ODZKing]

Installed the NGK plugs, lowered gap.   did a test run.   engine seems to start easier and idle better.   I'm going on a trip from nj to md Thursday so we will see what happens.

thanks for the advice.

Now, when you say you lowered gap, what exactly do you mean? Example being, mine are currently spec at .35. Where would you go with that?

[flyinlow]

I  have had good results with the NGK BCPR6ES In Eddy heads. .040" gap . Tried .050 once , no notable  difference (MSD 6425) The ground electrode geometry starts to look strange past .050 gap.

The old HEI plugs that came with .060 gap where designed for that gap.

[mopar0166]

I reduced my gap from MSDS recommended .055 to .041.   Drove it a ton during cruising OC, seemed to start easier, but I noted it ran a tiny bit hotter.  I didn't change the timing etc but may play with that this week. 

[c00nhunterjoe]

Reccomended gaps are like valve lash. Its a starting number. Your particular build and geographic area may want more or less.

[bee1971]

I called the NGK Tech Line

432 Stroker - 10.5 to 1 Compression

They asked a few questions , 30 second conversation

Told me BKR 6E

Replaced the Champion RC12YC that I had in since break-in and about 100 miles when I pulled them out

[justcruisin]

Pretty sure that's the same plug as discussed, as far as I know, BCP and BK is one and the same. Although there is something telling me one is marginally shorter overall than the other