Block Drain Plug Mystery

[edwardc]

When I traded in my dead late-model (1976) v-drive short block for a Moyer rebuilt v-drive short block, it came built as a late-model engine, but used an early-model block. This was verified by multiple means: Block casting stamp of 1967; Lack of an oil fil cap at the flywheel end; Lack of a distributor hold-down bolthole on the block's accessory drive shroud.

Now I find there's another difference in the blocks. Where the rear cooling jacket drain plug should be, there is nothing. There is, however, a similar plug located approx. 1 1/2" to 2" further towards the rear of the engine. This places it squarely behind the accessory drive. The old engine's plug was positioned such that a long 1/8" pipe nipple could be fitted to it and it would come out in the space between the accessory drive's pully and the accessory drive itself. This is impossible with the plug that this engine has.

So, I have a couple of questions:

1. Is this inaccessable plug actually a coolant drain plug, or is it another oil pressure port?

2. If it is a coolant drain, what do early-model engine owners do about extending it?

[67c&ccorv]

I would love to have the lengthened drain extension on my 1967 but as you have discovered it just ain't possible with the early model motor.

The problem I have is getting a wrench on the plug to open or close it...the only possible way to do it easily is with a drain plug that has a lengthened hex head.

You may have to get a machinist to make up a few for you.

Cheers!

[edwardc]

So, I take it that it is a drain plug. I was thinking about trying a hodge-podge of elbows and nipples to route it out, much like you have to do with the forward drain behind the starter.

Maybe a close street elbow, a short nipple, an elbow, and a long nipple could serve to get it out where you can reach it. I only wish I had caught this while the engine was still on the bench and not installed in the boat.

[Will Jacocks]

Use a suction tube and drain it all out through the dipstick, for the oil that is. Not sure why you would need to do anything if that is water plug.

[edwardc]

Use a suction tube and drain it all out through the dipstick, for the oil that is. Not sure why you would need to do anything if that is water plug.

I already have a very effective oil drain setup through the oil pan pickup via the external oil filter.

Normally, the only time you're concerned with the block coolant drains is when you want to flush the block. But in my case, I have a different reason. Since I'm installing a newly rebuilt engine, I'm taking the opportunity to add fresh water cooling. I plan on using automotive type antifreeze due to its corrosion inhibitors. But the stuff is toxic, and cannot be allowed to simply drain into the bilge and be discharged overboard. I want to add a convenient drain so I can catch the coolant and drain it below the level of the engine-mounted coolant pump before changing the pump's impeller when necessary. This way, there will only be a small amount of coolant to catch when I remove the pump's back plate. This can easily be caught in a small container wedged under the pump.

If I don't drain the block first, the whole coolant system will try to drain out the back of the pump, overflowing any container I can wedge under there.

[baileyem]

block drain - early model

Ed,

On my 1966 A4, I have replaced the plug with a brass, radiator drain petcock. It works well for me and does not require removal unless I want to 'rod-out' the drain. It is not as accessible as an extention, but it is better than trying to remove/replace a plug.
I am sorry that I don't have a picture and the boat is still under wraps.....it's still winter up here.

Mike

[ndutton]

Ed,

I've been considering 2 small valves at the inlet and outlet of my coolant pump for the same reason. The valves would be similar to the small bypass valve Moyer sells. Closing the valves isolates the pump and spillage would be limited to the pump itself.

Haven't done it yet, I'm in the head scratching phase. When necessary I'm currently using small C clamps with plywood pads to squeeze the hoses shut. Instead I may fashion some clamps with wide ears and keep them in the tool box.

Just thinkin'

[67c&ccorv]

Ed,

On my 1966 A4, I have replaced the plug with a brass, radiator drain petcock. It works well for me and does not require removal unless I want to 'rod-out' the drain. It is not as accessible as an extention, but it is better than trying to remove/replace a plug.
I am sorry that I don't have a picture and the boat is still under wraps.....it's still winter up here.

Mike

My 1967 A-4 used one of those rad type petcocks but I find they tend to clog and/or the ears break off if you are not careful when opening or closing them.

Wondering if it would be possible to rig some sort of 1/4 turn ball valve into that space or run permantly attached tubing that would lead to a location where a quality valve could be mounted.

I have to drain my block for winter as I am raw water cooled up here in the Great White North.