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Discussion Starter #1
I have just taken the heads off, because the engine started to let off white smoke through the exhaust. Had a serious overheating on the highway due to a broken freezevalve just before this.

Found a crack in the one of the heads around a coolant passage in one of the heads gasket surface facing the block. Guess this is the reason.

Got a pair used heads from a guy in my area that might be restorable (they are said to be from 68, mine is a 70). They have the same castingnumber, ending with 250.

In the 68 ones there is extra holes in the exhaust ports that are not in the 70 ones. These holes are just smaller than a quarter of an inch. Anyone now what theese are for?

All the best,

Cardan
 

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Those holes are the discharge ports for the air pump. Most manufactures placed the air pump fittings in the exhaust manifold. Cadillac cast them into the head. When I fill them, I use a torch and melt aluminum from an old piston to pour them full. It isn't absolutely necessary that they be filled if you don't want to. Dan
 

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air injection ports

I have the same situation with Ford engines. What I do is tap out the hole and screw in a grade 2 bolt with a dab of devcon or JB Weld on it then grind it and the bump into oblivion.
 

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Discussion Starter #4
Thank you for your replies!

So this means that they are some kind of smog heads. Can they still be from a 68?

All the best,

Cardan
 

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Cadillac could see the writing on the wall concerning the coming federal emissions standards. Just about all of the Caddy heads had the passages cast into the head. If an application needed an air pump, the holes would be drilled. The only head I can think of off hand, that didn't have any smog rails was the 70' Eldo 950 casting.

Your replacement heads may need the holes in the end of the heads, where the air pump piping connected, plugged off. A trip to the parts store for the correct size soft plug will fix you right up. If it's late Saturday night, and the parts store is closed, a dime with a little JB weld works great.........Dan
 
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