Hello all,

First, thanks many times over for all the good advice freely offered to me on this site. My project would never have gotten to the point of the kind of little problems I have now if y'all hadn't directed me to solutions to the big ones!

My application is slant six block casting 2806830-1 (with the xtra ribs). Numbers on boss under number six plug at firewall end on passenger side are 2B212047. Problem is oil pressure gage sender hole in block.

In my long used engine that came in my '64 d100, the oil pressure sender is screwed into the block in a hole that has been made in a flat boss on what is likely an oil gallery on the block. THe gallerey is a half round part of the casting that sticks out beyond the block wall. Above this gallery the block wall rises flat and straight up to the top of the head, about 4 inches of rise.

In my present engine in use the boss is drilled and tapped and the sender is inserted so as to stick "straight up" , or pointing to the top of the block. In my new block the boss is not drilled. There is a 1/2 inch diam fine threaded hole going INTO the block. Its direction into the block is such that if you drilled on through everything, you would come out on the driver side of the block. THis is perpendicular to the hole drilled in the boss which if extended, would come out of the gallery and hit the ground.

Of course, the sender is about 1/4 inch in its threaded part so will not readily go into the 1/2 inch hole without an adapter. HOWEVER, I am not even sure the sender does go in the large hole. In my in0-use engine, the large hole is plugged.

SO, is the large hole an oil hole, or a water jacket hole?

If I have to drill and tap the boss to install the sender, is this drilling done just as in mild steel...(I have not drilled cast iron so don't know what lube to use on the drill bit, etc) Because I would have to have a drill bit about a foot long to get down to the boss past the head and so on, it would make life easier if I could use the existing block hole, add a tee, and do both mechanical and electrical gages in that hole.

I KNOW someone knows all about this but it has me stopped today!
rock
'64d100

if memory serves, the later motors(?) have the sending unit mounted in the oil pump. i don't know the break, but my '63's had the sender in the block (blocks with 3 freeze plugs on diver side) and my '73 had it in the pump (5 freeze plugs on driver side.) not sure about the "mystery hole."

-james

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Pictures would definitely help here. Only the early 60s motors had the oil pressure sending unit in the block. Later motors (at least 68 and later) had the oil pressure sending unit off of the back of the oil pump. Are you sure you aren't talking about the anti-freeze cleanout plug? There is one on the passenger side of the motor near where the oil sending unit used to mount.

On later blocks there's a 1/2" hole with a threaded pipe plug in the low part of the block above the oil gallery...depending on how 'clean' you slant is, the passage my be clogged with rust, flakes, and trash (so far I have pulled 'the plug' on seven slants and nothing comes out until you use a hammer and phillips screwdriver to make a hole and run some wire in there to make a passage...it becomes nice and unclogged after 2 days in the hot tank...)

-D.Idiot

That reminds me, the same guy who installed the Dusenberg vibration dampener on his 170 installed a little water-tap type valve in this radiator fluid drain hole. Much easier to work with than the funky 8 sides pipe plug Mopar instlled. It was pretty cool to see a little faucet hanging off the side of the block!

I can confirm that on my '74, the oil sending unit is mounted horizontally on the rear of the oil pump. I installed a brass tee on the pump, one leg for the oil sender and one for the mechanical gauge.

Jerry

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There's a difference between ignorance and stupidity.
Ignorance is not knowing any better.
Stupidity is knowing, yet doing it anyway.

The engine block location for the oil pressure sender was a '63-'65 deal. There is a TSB issued in '65 shortly after production location of the sender moved back to the oil pump, saying to move the sender to the oil pump location on '63-'65 vehicles if leaks and/or odd oil warning lamp behaviour is encountered. I think your best path to take is to mount the sender in the oil pump and plug the unused block hole(s).

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

a radiator petcock fits as well.

-james

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Guys...

THANKS for fine input from what time has shown me are really good thinkers here!!! Y'all solved my problem. Me, being an old timer had never worked with "new" blocks that used an anti freeze drain AND had sender on pump. I got 3 '64's about 1968, and '64's are all I ever worked on until now. That is why I have some questions on occasion that must make folks wonder "should this guy hold a wrench or not?"

What is described in the replies is obviously what I got in the newer block I am working on now. (After reading DD's block article) The antifreeze hole is nice and clean, cause the short block (from eBay seller Robzet after a tip to me on this board) was REALLY cleaned and rebuilt very nicely. It is so clean that the 1/2 inch hole sure looked like a water jacket entry to me so imagine how I was scratching my head after only ever seeing a sender IN the block! It was one of those things that makes you say why didn't I look at that when I was fitting the head...I always assumed it was the oil sender hole until here at the end of the project.

I have always descaled and backflushed my cooling systems every frew years by using a heater hose tee and garden hose and leaving radiator cap off for outflow. Here in the south we have soft water, i.e. basically rainwater, so I keep a 65:35 antifreeze ratio to water and try basically to eliminate rust. The idea of a little radiator drain on the block is intriguing, but I have learned from the forum that my backflushing may not be the thing to do any more.

Thanks a millyun!
rock
'64d100