Looking for thoughts on a spark plug change I made recently. Originally built the engine and ran R44LTS AC Delco plugs with the gap that they had out of the box (0.040" I think). Recently moved to TR6's gapped at 0.040"-0.045" trying to remove heat from the combustion chamber. Until the motor is good and warm (roughly 10-15 min of runtime), it seems to have an intermittent misfire. Not a full-on dead cylinder miss, but a noticeable incomplete combustion once every 5 seconds if I'm cruising at 2000 rpm. Also, I've noticed difficult hot starting with the car, I've read this can be an issue with TR6 plugs. Any insight on this or others with similar issues and suggestions?

Engine Specs:
LQ4 6.0, flat top piston
11.3cr
799 cnc ported heads
231/238 .629/.615 112+2
Long tube (w/ header wrap)

 

Are you sure that you bought legitimate NGKs? eBay and Amazon are flooded with counterfeits.

https://ls1tech.com/forums/general-l...ark-plugs.html

 

Pretty sure, ordered from JEGS.

 

Might worth pulling & checking the plug in the cylinder misfiring.

~23 years, ran NGK TR-55's or TR-6 in five set ups in three different cars with only one issue. Had a misfire once and found a TR-6 had a cracked insulator. Replaced plug and issue went away. I'm guessing that plug was dropped at some point.

 

Was this misfire there before the plug change?

 

Could also have a coil going bad. Had a similar situation. Mine was a bad coil.

 

I have exclusively ran TR6s for the past 4 years with only a little difficulty with hot starts. Curious as to what is causing the issue.

 

I'm running NGK TR6IX sparks plugs. No issues. LQ9 TEA 243 milled heads, SRD camshaft, long tubes.