Long story short. I galled the spark plug threads on my TF heads. I had a local machine shop install inserts (not heli-coil). Now it looks like the plugs are approx 1/8" (1.5 turns?) short (shallow in the comb chamber). How deep do the plugs need to go into the combustion chamber? Need help on this one. I took vacation time to put this motor back together and back into the car. Thanks for any help guys.

 

the spark plugs extend into the combustion chamber, so the threads need to go all the way into the combustion chamber, so the plug will be seated properly and seal on the outer part of the head.

hth

andy schuck

 

Yes it does, thanks. I looked at other non-LT1 heads I have and the first thread on the plug lays flush with the bowl. I am taking these back these back now to see if they can countersink the insert so the plugs extend into the chamber. Thanks again.