No clue!

[Fathead Racing]

Ok, someone has to set me right. I have AC Delco plugs in my BWR heads. The plug number is 41-630. Now I know the 630 number is the important part. A member that knows his way around suggests I run a colder plug, one step colder to start. I have been all over the AC Delco web sites and am now more confused than ever. I don't even know how I ended up with the plugs I have now! HELP!

 

[Don Jacks]

Ray,the second number indicates the heat range on most AC plugs.In your case you'd want a 40-630 AC.Go to a near by parts house and look at their spark plug cross reference catalog.Look up your plug and see what it interchanges to and in the case of all but NGK go down one number .With NGK's [excellent plugs by the way] go up one number for colder plugs NO Champion,Bosch Platimum or any of the "trick" or irredium plugs since you're running leaded race gas.

 

[dm62409]

I don't know if AC Delco has racing plugs anymore. Just going to throw out a suggestion, NGK , the -7 is almost stock heat range for a 11-1 compression engine, the -9 is more for a 14-1 engine, I would suggest the -8 heat range for the 60 Ray. The 5671 number is not an extended tip, if you wanted an extended tip plug it would be 5672 . The larger the dash number the colder the plug. These are the smaller 5/8 hex to fit the BWR's. ( I know the -7 is hard to resist with 409 in the stock number. ).

 

[Fathead Racing]

Don, in AC Delco lingo the 41 is the Delco number for spark plug. I can find no 40-630 Delco plug.

 

[Fathead Racing]

Dave, am I to assume I need the extended tip?

 

[dm62409]

The AC Delcos that I do have are the large 13/16 hex and won't work in the BWR's

 

[dm62409]

Dave, am I to assume I need the extended tip?

I wouldn't use the extended tip in a racing application.

 

[Fathead Racing]

The AC Delcos that I do have are the large 13/16 hex and won't work in the BWR's

That's why I have the 41-630's. But I don't think these are the plugs I should be running. I'm going with -8 NGK's. Thanks Dave. I'll study up on the NGK plugs.

 

[Fathead Racing]

Just ordered the NGK plug, https://www.amazon.com/gp/product/B071NB6W2X/ref=ppx_od_dt_b_asin_title_s00?ie=UTF8&psc=1

 

[Don Jacks]

You'll be happy with them Ray.

 

[Fathead Racing]

I have used NGK plugs in the past for my Honda motorcycle's and some of my cars/trucks. This will be the first time for the 409, any of them. If it's good enough for Mills, it's good enough for me.

 

[Ishiftem]

Just ordered the NGK plug, https://www.amazon.com/gp/product/B071NB6W2X/ref=ppx_od_dt_b_asin_title_s00?ie=UTF8&psc=1

Those are what I run.

 

[boxerdog]

Resistor vs. non-resistor is not important?? Just asking.

 

[Don Jacks]

Not really an issue with today's ignition systems,but I'd want resistor plugs just to keep the electronics happy.

 

[Ishiftem]

I run the racing plug which is nonresistor. I’ve seen tests where the resistor type cut spark by quite a bit. In a new car I can see where a nonresistor would play havoc with all the electric doo dads.

 

[Fathead Racing]

I run the racing plug which is nonresistor. I’ve seen tests where the resistor type cut spark by quite a bit. In a new car I can see where a nonresistor would play havoc with all the electric doo dads.

As you see I ordered the race plug. Is that resistor or not? There is an R in the number. Why would they do that? I didn't know there was an option. Dave mills runs the same number plug! With the R designation.

 

[Ishiftem]

In this case the r stands for racing. They are non resistor. It’s a great plug!

 

[boxerdog]

I'm so far behind I've been running MSD iridium with race gas (leaded) but I haven't really noticed any problems.

Upon digging through MSD tech stuff, it seems like they prefer copper plugs with resistors. So now I feel like changing plugs just because why not??

 

[Ishiftem]

Didn’t know msd wanted a resistor plug. Is that for analog or digital box?

 

[boxerdog]

I think it was in the 6AL tech material? I think I had heard that before, and also I saw something referencing no solid wires. But I didn't bookmark it or anything. Could also go back to old standby 3923 or 3924 Autolites I guess.