All Small Six NGK Plugs that suit

[Teditor]

I have an 1978 Fairmont GXL XC 4.1 with Extractors, bottom stock end, an Alloy head (XD or XE not sure) ported and polished and port matched to triple 45 DCOE Sidedraft Webers, I was running NGK BP6E S Plugs (I think these were for the cast iron head and probably didn't seat properly and ran black, along with backfiring), I have just put a set of NGK BP5FS plugs in (supposedly correct), improved already, but seems confusion on what is recommended, any assistance appreciated.

 

[chad]

have U tried the recommended but (same) ofa different temp range?
(looks that way w/the '5' & '6')
Post upa pic of how they've burned...

Sometimes I go thru quite a number of plugs (all ways round the book recommended) to get
good burn + stop watch better (need both)...
U need even more trials W/that head. Do some around the off oe head U R uesing as well?
The 'plug chop' is a useful technique too.

Last, I have not been there ina long time but these are the best guys to ask

Aussie Ford Sixes

Inline sixes from down-under or south of the equator.

fordsix.com

(we had folks there 9 d ago)

 

[PSIG]

For the heat range, there are several ways to determine. This is one from Mike Canter:

Spark Plug Heat Range
If you keep on adding timing until your finish MPH falls off, but you still have no color on the plug’s ground strap, but the porcelain has good color then your plug is too cold.

If you have lots of color on the ground strap, but the porcelain is clean and white, then the plug heat range is too hot. The heat from the plug is cleaning off the fuel ring from the porcelain.

Your application is for street, with much greater range demands, so consider that in how you're testing for heat range. Read the whole thing here: https://www.dragstuff.com/techarticles/reading-spark-plugs.html

From Jeff Smith, the whole point of heat range:

The key to a heat range selection is related to selecting a plug that will efficiently burn-off carbon deposits from the center ceramic during normal use of the engine.

I'll note that Jeff's default and mine are a bit different. Jeff's goal is the same, but I use the coldest plug that will stay clean. He uses the "hottest that will survive". Unfortunately, IMO that's dangerous, as a too-hot plug can induce detonation or destructive pre-ignition. A too-cold plug will not stay clean in your normal use, resulting in (at worst) misfire if they foul. I think that's the safer route or direction to approach, but your call.

Another good reference to help fill-in the holes: https://www.crankshaftcoalition.com/wiki/Reading_spark_plugs

Finally, as heat range is strongly affected by other factors, such as tuning, here's this:

 

[Teditor]

have U tried the recommended but (same) ofa different temp range?
(looks that way w/the '5' & '6')
Post upa pic of how they've burned...

Sometimes I go thru quite a number of plugs (all ways round the book recommended) to get
good burn + stop watch better (need both)...
U need even more trials W/that head. Do some around the off oe head U R uesing as well?
The 'plug chop' is a useful technique too.

Last, I have not been there ina long time but these are the best guys to ask

Aussie Ford Sixes

Inline sixes from down-under or south of the equator.

fordsix.com

(we had folks there 9 d ago)

Thanks for the help, I have posted the question on the Aussie forum.

 

[Teditor]

For the heat range, there are several ways to determine. This is one from Mike Canter:
Your application is for street, with much greater range demands, so consider that in how you're testing for heat range. Read the whole thing here: https://www.dragstuff.com/techarticles/reading-spark-plugs.html

From Jeff Smith, the whole point of heat range:
I'll note that Jeff's default and mine are a bit different. Jeff's goal is the same, but I use the coldest plug that will stay clean. He uses the "hottest that will survive". Unfortunately, IMO that's dangerous, as a too-hot plug can induce detonation or destructive pre-ignition. A too-cold plug will not stay clean in your normal use, resulting in (at worst) misfire if they foul. I think that's the safer route or direction to approach, but your call.

Another good reference to help fill-in the holes: https://www.crankshaftcoalition.com/wiki/Reading_spark_plugs

Finally, as heat range is strongly affected by other factors, such as tuning, here's this:

Thanks for the help, I have posted the question on the Aussie forum.

 

[Teditor]

For the heat range, there are several ways to determine. This is one from Mike Canter:
Your application is for street, with much greater range demands, so consider that in how you're testing for heat range. Read the whole thing here: https://www.dragstuff.com/techarticles/reading-spark-plugs.html

From Jeff Smith, the whole point of heat range:
I'll note that Jeff's default and mine are a bit different. Jeff's goal is the same, but I use the coldest plug that will stay clean. He uses the "hottest that will survive". Unfortunately, IMO that's dangerous, as a too-hot plug can induce detonation or destructive pre-ignition. A too-cold plug will not stay clean in your normal use, resulting in (at worst) misfire if they foul. I think that's the safer route or direction to approach, but your call.

Another good reference to help fill-in the holes: https://www.crankshaftcoalition.com/wiki/Reading_spark_plugs

Finally, as heat range is strongly affected by other factors, such as tuning, here's this:

Thanks for the help, I have posted the question on the Aussie forum.