We have a 51 Dodge pickup in the shop being restored, and the engine (Flathead inline 6) needs a bit of a freshing up. Pulled the head and during the cleaning up of the combustion chambers a hole of about 3/16th of and inch was uncovered in # 6 cylinder. No others, just #6. Turned the head over and there is a 1/8th pipe plug in the same approx location. Curiosity has a hold of me now, that plug has to come out of there. Sure enough they line up. You can see clean through. At first when I seen the plug, I just thought it was in the water jacket...nope. Customer has a manual for the truck, skimmed through it but didn't see anything pertaining to it. I have a couple of theories, (also know as guess's) as to what it is and for. I would like to hear your thoughts on it, or knowedge if you know for sure what it's about. I've been in the wrench pulling game for a lot of years but have never run across this "hole in the head" deal before. Although I have been accused of having a hole in my head a couple of times. It definitely looks factory, take a look at the pictures and post your thoughts. Sniper.
I'm thinking it might have been there to used that cylinder as a compressor?
I never thought of that, could be. I was thinking of more along a timing thing. I did see something mentioned in the manual about using #6 at TDC to set the valves, a hole for a probe maybe. Then again you could likely pull a plug to do the same thing. Still don't know...still guessing. I have yet to go through the manual and see if there is any mention of it or any 'tool' used in conjunction with it.
only one cylinder .. might be for a cylinder head temp gauge in a stationary or boat motor ..maybe?
The customer was lead to believe the engine is the original to that vehicle. By the look of it and how everything was still all hooked up, I would agree. Doesn't look like anyone has messed with it or made any changes to anything.
In the head there is a small pipe plug over the #6 cylinder. If you remove the plug you can drop a screwdriver down on the piston and see it rise and fall as you turn the engine by hand. This allows you to find top dead center.
#1 and #6 rise and fall together. You can tell which is on compression by the *woosh* of air out the plug hole.
When the piston is at TDC and #1 is on compression the rotor is pointing to #1 firing position.
By checking this way there is NO mistake about it. Timing marks can be wrong but this method is fool proof.
I'm thinking it might have been there to used that cylinder as a compressor?
I never thought of that, could be. I was thinking of more along a timing thing. I did see something mentioned in the manual about using #6 at TDC to set the valves, a hole for a probe maybe. Then again you could likely pull a plug to do the same thing. Still don't know...still guessing. I have yet to go through the manual and see if there is any mention of it or any 'tool' used in conjunction with it.
It looks like the spark plugs are over top of the valves.
In the head there is a small pipe plug over the #6 cylinder. If you remove the plug you can drop a screwdriver down on the piston and see it rise and fall as you turn the engine by hand. This allows you to find top dead center.
#1 and #6 rise and fall together. You can tell which is on compression by the *woosh* of air out the plug hole.
When the piston is at TDC and #1 is on compression the rotor is pointing to #1 firing position.
By checking this way there is NO mistake about it. Timing marks can be wrong but this method is fool proof.
Well that was interesting little exercise, thanks Carl. Hey Jarvis....what do you mean " a relief valve sorta thingy"....everybody knows it for firing spitballs on the ceiling, in auto class.
