Re: Spark Plugs

Posted by PackardV8 On 2011/9/9 10:24:17

Use a small scale with a slight hook on the end or some other suitable measuring device to measure the length of threads in the CYLINDER HEAD. MEasure one hole in EACH that is BOTH heads that is on the car.

U mite do it an easier way by using uing two eyes:
Tell us the casting number(s) on the cylinder head that is directly over the center exhaust port of the head. CHECK BOTH HEADS!!!

Note that it is entirely possible that after 50+ years that it could be ANY combination of 55 AND/or 56 heads on a 55 or 56 block.

Let me put it another way:
There is one thing, exactly one thing and only one thing that determines the which reach of plug that is needed. That is the length of threads int he heads.

Short of measuring the threads in the head then there is one thing exactly one thiong and only onle one way to determine the length of thread needed and that would be those very top secret casting numbers on the heads that noone ever seems to be able to read,reveal or for some reason seem to believe are so eternaly mystical.