Hole in the head

[Kaiser2boy]

My wife says I must have a hole in my head for buying this truck, what does she know anyway,,

However after I removed the head from the engine and got it back from the machine shop I notice a perfect 1/8 inch hole bored right up through the top of the combustion chamber . It terminates at a 3/8 inch fine thread plug on the outside of the head. If the plug is removed you can see right through the head.
It is in the #6 cylinder.
Anyone ever see that or have any idea what it is.

[maineSS]

That's the timing port- you find TDC by inserting a rod thru the port- be sure it's long enough to accomodate the entire stroke so you don't lose it inside, then rotate the engine til the rod stops moving up- that's either an intake or exhaust TDC point.

[Kaiser2boy]

Very interesting. Thank you.
I was thinking it was a hole that was drilled by mistake and plugged.

[carter davidson]

I believe the plug and tapped hole are a hold-over from the WC engine series for use with the then issued Timing Indicator.

Pic of indicator and test lamp:


From the manual: "Using the Timing Indicator over number 6 cylinder (Fig.50) bring the piston up on compression stroke until the piston is 2 degrees past top dead center.
Loosten the lock screw (3, Fig.51) and rotate the distributor body until the breaker points just start to open. This may be checked by means of a test connected between the distributor primary terminal and the battery "B" terminal of the voltage regulator assembly. When the points close the lamp will light and as soon as the points break the light will go off.

[Kaiser2boy]

The hole is in the # 6 cylinder so that is what it is.
I guess its a good idea because I can remember times when I would remove a sparkplug and slide a welding rod down the cylinder to achive the same thing .
It is just another interesting item about old school technology. Foolproof and simple.