There is a drain plug on each side of the block close to the motor mounts. Should be a 9/16" hex head. Use reasonable force on them, if you meet a lot of resistance stop.

Good luck!!!

 

If you pull the motor consider replacing the timing chain and gears. It is easier, neater and cleaner to do the chain with the oil pan removed as is the rear main crankshaft seal.

Good luck!!!

 

I just went through removing block drains on a 403. Leverage is your friend, felt very tight with a ratchet, easy with a swing bar. Penetrating fluid and heat as necessary. Yes, if the factory nylon coated cam gear timing set has never been changed, now is the time.

 

To my surprise the old mixture came out and was almost clear.
I think the correct way to use the acid or any flush is to add it to the cooling system then run the engine at high idle speed for 20-30 minutes. Heat and circulation is necessary for the chemicals to work. Occasional quick throttle openings will help the water pump to stir up some of the sludge.

 

yes. Is that because the stock nylon timing sprocket is prone to failing?

 

Thanks! I'll be careful if i want to remove the block drains. I absolutely do not want to crack the block using too much force opening these plugs😵‍💫

 

It is staring to work! Temps start to drop continiously.
today my heavy duty fan clutch from Rockauto arrived.
i'll install that later this day after work.

 

Glad to hear it.

 

Awesome, please keep the post updated til closed for future reference.

 

Nice work!

 

Installed the new fan clutch the other day and it makes a hughe difference. Temp is hoovering between 175 and 200 degrees. Ambient temperature here is 82 degrees.
next weekend i'll swap in the new 3 row aluminium rad and the 180 degrees stat again and see if that will also help a bit. For now i have removed the acid and i will replace that a couple of times with water and soda to neutralize the acid and remove traces of it out of the cooling system. I'll report the results here of course.
thanks again for all your helpful input!

 

Awesome!

 

1973Delta88, I'm glad you've made progress but I looked through the replies and I don't think you've addressed this response. Installing a fan shroud is the single easiest way to improve low speed cooling. Almost all cars came with them (yeah, I know there were a few that didn't) and almost every car that has low speed cooling issues has had it removed.

 

I seemed to have overlooked your response. Sorry! And thanks.
this car does have a fan shroud,and as far as i can judge it looks like it's the unit the car came with from the factory.