318 Block Leak

Tech Question

Billy Martin, Ann Arbor MI, 1972 Plymouth Valiant 318

Hello, Since you guys are the guru’s of the mopar scene Ifigured I would come to you with my dilemna. I have a 318 valiant in whichI put a new Edelbrock intake on, Holley carb, Hedman headers and a fewcosmetic changes as well. Problem is that I filled the radiator withcoolant and before even starting it was leaking by the back of the block. Icannot tell where exactly it is coming from. I looked under the car and itseems to be dripping throught the trans/engine mating surface (even though Inever even touched those bolts!). Can you help?

Thanks, and keep up the great work!

Billy-

Hmmm. Assuming that the engine is original, or hasn’t been rebuilt totallyin many moons, the problem is surely that the core plugs in the rear of theblock have rusted through. These take about 2 minutes to change — once youhave the back of the block accessible (i.e., transmission, bellhousing,yada, yada.)

I know this isn’t what you wanted to hear. At least now you know why theysell those “lifetime” brass core plug sets!

I should also mention, even thought it doesn’t exactly fit your descriptionof the leak location, that the heads are syymetrical, and have waterpassages at the intake flange front AND rear. The intake manifold simplyblocks off the rear pair. But if the gasket seal is screwed up somehow, Ican visualize coolant running down the back of the block, into the clutch /t’converter housing, and out the bottom.

Rick