Hot Rods Spark Plugs

Hi All,

Probably an old subject, but was after some specific recommendations please. Have an iron headed SBC 1970 Vintage I think, 010 block, running 671 Weian blower, NOS and Vertex OAC Magneto. Will be street driven mostly, and occasionally track squirt. But after the best recommendation on plugs for street driving, prefer NGK, currently running Autolite which seem OK. A little confused regarding projected ends, no projections, suppressed blah blah blah etc. Any help welcomed and appreciated.

 

What heads are they? They changed in 1970 to use the small tapered seat plugs, earlier heads used the gasket type plug.

I've put a lot of miles on blown big blocks with normal AC plugs (back when they were US made). If it's 1970 or later heads, R44TS should be fine. That's one heat range colder than stock R45TS.

R means resistor plug
4 means 14mm
5 is the heat range
T means tapered seat
S means projected nose
I expect there is an NGK plug with these specs, but I'm not familiar with them.
see if .035 gap works ok, might need .030 for good low speed operation.

 

Always, read your plugs and adjust accordingly.









Bones

 

Careful on the plug gap.
Vertex mags, even with the OAC coil don't like big spark plug gaps.
You might get away with .030" on the street, but if the engine breaks up at higher rpms during your track...Squirts...close the gap down to .025" or so.

Vertex mags also like copper wires (see "Packard 440"), over spirol wrapped wires.
Plug wise, run what you like on the street. You don't provide much in the way of engine specs, but other than running a "non-resistor", any plug should work fine on the street.
If you are running a lot of compression, and or boost pressure a short tipped plug might be better, But a normally built engine for the street, either projected OR standard tip location will be fine.

Mike

 

thanks, I was wondering about the gap...

 

My 1970 186 heads take the kind with the washers
Autolite 85 was the number

 

Thanks for that info @squirrel. Kind of embarrassing, but I thought those numbers/letters were just some kind of part numbers. I had no idea they actually told you something.

 

Champion and AC both share the system that the lower the number the colder the plug. If memory is right NGK is opposite, the greater the number the colder the plug is. Not sure about Autolite, haven't used them since the days of my last FE motor, that was 1970.