spark plug options

**WILMASBOYL78** · #1 10-19-2025, 03:16 PM

Time to put a fresh set of plugs in the 70 TH400 L78 car...stock motor, good fuel.

Just wondering what you folks like for this...

Thanks, wilma

**pdphilson** · #2 10-19-2025, 05:25 PM

could be wrong -- was'nt 70 a transition year from gasket to taperseat ? so becareful

**WILMASBOYL78** · #3 10-19-2025, 05:51 PM

Yes...the small 5/8" peanut plugs with tapered seat are the ones in this car. 291 rectangular port heads...

Ralph Spears · #4 10-19-2025, 06:06 PM

What does the owner's manual call for

**1967 4K** · #5 10-19-2025, 06:18 PM

NGK is what I use in my L78.

**169indy** · #6 10-19-2025, 07:25 PM

I use: NGK 2635 GR4 V-Power Spark Plug
for my 1968 L78
Not a tapered set up.
There must be a tapered version.

**1967 4K** · #7 10-19-2025, 07:36 PM

I used recommended brands like AC, Autolite, Champion. All would foul after a short time of use. Changed to NGK and no problem.

Ralph Spears · #8 10-19-2025, 08:12 PM

What is the AC spark plug number that is listed in the owner's manual

**markjohnson** · #9 10-19-2025, 09:45 PM

Just bought a fresh set of NGK’s for my 291-head’ed LS6 last week so here ‘ya go.

**WILMASBOYL78** · #10 10-19-2025, 10:45 PM

That's great...just the info I needed. Will hit the parts store tomorrow.

Thanks

The Following 2 Users Say Thank You to 1967 4K For This Useful Post:
169indy (10-19-2025), napa68 (10-19-2025)

The Following User Says Thank You to markjohnson For This Useful Post:
RPOLS3 (10-20-2025)