Recently had 350 professionally rocket rebuilt. Have finally got it installed and running, however we are seeing coolant leak from the back side of the engine. Any ideas where it could be coming from?

 

Take it back to the "pro", have them figure it out for you! Could be a lot of things- cracked head, block, bad gasket- intake ( my guess), head etc. Is it coming out from the back of the block where it mates to the torque converter ie: water dripping out of the torque converter dust cover or do you see water running down the "outside" of the block?

 

It could be a heater hose, loose intake bolt in the back, intake manifold gasket, freeze plug, you need to investigate with a flashlight and a mirror.

 

I agree that you need to be more specific as to where at the back of the engine the water is leaking.

If it's on the passengers side, the heater valve perhaps?

 

Installed a 455 build in my 69.New heater hose and control valve. The brand new control valve took a pee after about 200 miles.....+1 on checking the heater control valve..

 

Thanks for the responses. The leak is originating under the bell housing. Spoke to the rebuilder. He says that sometimes the coolant will trickle by the new freeze plug(s) which is silver. However, once the engine comes up to normal operating temp the plug, 99% of the time, will seal itself. There are 2 freeze plugs on the back side. Once were fully operational we'll run it awhile and see what happens.

 

if its coming from the bell housing area it seems to be a leak running down from the intake coolant nipple the freeze plug is more forward of that but should be able to rule out the nipple with a dry finger and flash light

 

My opinion is that if a freeze plug is installed properly than it will not leak.
I'm not a professional engine builder, though.

 

^^^ x2

 

I've had good luck using The GM stop leak tabs.

 

I think he's trying to mug you off. Freeze plugs shouldn't leak if properly installed. Period.
Otherwise when we go to the garage and see a puddle of coolant under the car we would just say; "Hmm... cooling system seems fine, no oil leak though, better take it to the shop and see why not."


If his freeze plug installation is anything to go by I wouldn't have much faith in the rest of the engine..


Roger.

 

So the builder is suggesting that the plug will heal. Interesting