Ok, I never got why it was OK to put aluminum heads on an iron block... isn't that what was wrong with the Vega???

What is different?

 

In what respect? The head gaskets would completely seperate the iron from the alum, so you wouldn't have electrolosys (sp.) The newer gasket technology allows for the quicker expansion rate of the aluminum without tearing up the gasket. Also, the valve seats will be another harder material pressed into the alumunum, so that it doesn't wear the seat.

Does that answer it? If it doesn't, let me know what info you're looking for specifically. I have a SBC rebuilding book here that I'm reading, the info might be in there.

Matt

 

I didn't really have a specific question... I was just confused as to why it was the Vega's major problem, yet everyone today wants aluminum heads on their SBC!

So head gaskets are the main change? Why didn't they think of that back then!?

 

The Vega engine had an iron head with an aluminum block. The cylinders were not steel-lined, rather an etching process was used to remove aluminum from the surface of the matrix and leave a thin layer of the hard silicon. It would work as long as nothing got into the cylinders like dirt or antifreeze.

The first two years, they had a lot of head gasket failures because of poor coolant flow causing excessive aluminum expansion between the cylinders, over-flexing the gasket. Coolant then got into the cylinders and wiped out the silicone surface. '73-up they cut a slit between the cylinders at the gasket sealing surface and solved the problem. By then their reputation was shot.

In the late 70's and early 80's, there was a cottage industry lining Vega blocks with steel liners. There were also modifications to either the head or pistons to provide some quench, which greatly improved power. Was a half-way decent engine then, with cam and exhaust upgrades. But, Nader got his way after '77.