ZR-1 Net Registry Forums - Spark plug gap

Quote:

Originally Posted by efnfast (Post 153619)

This was the answer I got from Mr. Haibeck

Hi Steve,

For high load operation I recommend a spark plug that is one AC heat range cooler than the OE plug. The best spark plug is the NGK TR7IX. Part number 3690.

It has a tapered seat. All LT5's are machined for both tapered and flat seat plugs. Carefully open the gap to .050"

Best of luck.

Marc

You have to be careful when you say that.

Actually, all LT5 heads were not "machined" for both types of seats. The heads were cast with spark plug mounting and threads designed for both, but on the 90-92 heads the taper seat is not there.

When you use taper seat plugs in early heads for the first time you purposely overtorque the plugs then back off a turn and retorque to the normal tightness. The "first-time-overtorque" forms the taper seat in the head.

Once you do that, then the head will accept either flat or taper seat plugs.

As for gaps, since my engine doesn't have a dual mass, in search of more stable idle and less gear rattle, I installed more powerful ignition coils, lower resistance MSD Super Conductor wires then opened my plug gaps up to .070-in.

As for plugs, I use a Denso IT-22 which, heat range wise is close to that NGK 7 which Marc likes. Use them in LS7s, too.