[street rodder 1937]

Hey Guys I have a bbc with a 6-71 blower.I just changed the spark plugs and noticed the electrode on the number 7 spark plug was bent . The peice right above was fine,not bent or push down touching the electrode. Car runs fine.What would cause that and is there anything i can check to know for sure the engine is ok.

[61 chevy]

i would start with a leakdown check of the engine..if you have a zero deck or close to it, and a long tip plug..this can happen. Hope everything checks out fine, it's the wrong time of year for a teardown.

[Rick WI]

Two reasons that will happen, The piston kisses the end of the plug, meaning the plug reach is too long or a piece of piston or valve went through the motor but kissed the plug on it's way out.

The third reason that can happen is it's put in that way and just missed.

Gut would be the third reason. You'll know soon enough once you check it in a day or so after running.

[powerrodsmike]

If I drop a plug when I am installing it, Chances are it bends the electrode. I always check it before I install it. Just a thought, mikey

[docvette]

Doc here,

Something small could have nicked it passing through the induction system (like a throttle plate butterfly screw fell out) and spit it out the exhaust..

Not sure if a heavy Detonation would do that on a blown engine or not..But it may be something to consider..

Most likely, as was said , It probably went in that way and you just missed it..maybe mashed it on a header trying to find the plug hole..

I do know if you over~torque the Plugs the gap can spread, but never heard of one closing without help..

Doc

[IanRiordan]

If I read this correctly it's the centre electrode not the ground electrode that's bent. I've seen this on propane engines with too much total timing, propane likes a short fast curve and seems to detonate up high rather than under load. By all means do a leak down test, but if the insulator is blistered you may have detonation.
I seem to remember some blokes using 2 different heat ranges in the same engine (BBC) in the 70's.