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chasing spark plug threads on head?

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Jer

Jer

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I have the head off my 74 (1275) because the #2 would not come out since I got the car just over 2 years ago... penetrating oil did nothing so finally I bit my lip, hooked up the impact (on light setting) & walked the plug out (back & forth) it didn't break off, but the threads on the plug itself had a slight dishing near the middle (I assume PO over torqued or something), I can start a plug into the socket on the head & then it starts to tighten up...
I want to chase the threads on the head - anyone know what tap size I would need?
 
Can't remember what size. But most auto parts houses have spark plug thread chasers. Usually one that is doubled ended for the two normal size threads.

Don
 
Do get a thread chaser, not a tap. The chaser will clean and somewhat reshape existing threads with little danger of cutting a whole new thread which could be a disaster. Don't ask how I know this.
 
Thanks for the advice on the chaser, I will get one next time I'm at the auto parts store !
 
It's 14mm but I forget what pitch. Last chase I bought cut like a tap and made the hole too big.
 
Pretty sure the pitch should be 1.25.
 
Take in the correct plug and if your parts store is any good they ought to be able to get it right!

Kurt.
 
Got a 14mm/18mm chaser at advanced auto parts last week, past weekend, I tried it out (the 14mm) & worked perfectly, the only debris I seen was dirt, not fresh metal shavings! ran it thru all sparkplug holes, reinstalled the head & installed new plugs - all good, Thanks for the advice :smile:
 
Glad to hear it worked out for you.
 
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