Hello, I have a 1969 Olds Cutlass Supreme, with a 455. The motor was rebuilt about 10 years ago. Unfortunately, the car had to sit for about 7 years after the rebuilding of the motor. The Edlebrock Aluminum radiator was toast, replaced that and the water pump. There was quite a build of calcium, etc. in the water jackets, I cleaned and flushed them before placing the new Aluminum intake on. Then, I realized I never removed the engine block drain(s) to flush what ever was in the lower water passageways. I removed only one engine block drain plug on the passenger side towards the front of the car just below the freeze (expansion) plug and flushed it until the water was jetting out of it. My question is this ~ Do I need to remove the one behind the motor mount next to it, as well? and are there other plugs on the driver side that I need to remove, or is removing one sufficient for cleaning and flushing?

I looked in my 1969 Cutlass Factory Manual, and the interwebs and found snippets of water jackets, etc. but not a really clear cut-away of the water passageways and how they connect inside the block. The car has always ran a little warm around 210.

thanks as always for any direction

-steve

 

I think one on each side front or rear shouldn't matter. Let's see what others say CRC ThermoCure is an excellent flush but can't be used in freezing conditions.

 

The water jackets on the two sides of the block only connect through the water pump and the intake manifold crossover, so yeah, you should pull plugs on both sides.

 

Thank you, this is good info, I will pull the plug from the driver side.

 

Dont have to worry about freezing conditions, since I live in Phoenix AZ. thank you for the reply

 

Went out and looked at the drivers side, and

there seems to be no engine drain plug....looks like it was a delete on this block for whatever reason? maybe this was a replacement block? (see pix)

 

Also no engine drain plug between the motor mounts on the driver side, like there is on the passenger side. I couldn't see one behind the starter, but I didn't drop the starter either. I just took a quick peak with a cheap scope

 

I recently flushed the coolant in my 71 98 because I replaced the head gasket. I didn't check for block drains on the 455. The crud I got out of the cooling jacket was surprising. Just keep flushing with distilled water until it runs clear.

 

The plug is probably behind the motor mount. I have blocks that have plugs in both locations on both sides.

 

Welp, I looked again, and sure enough the other one is behind the motor mount and beside the starter....at least there is one on that side.

thanks again all.

-steve