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Old 05-08-2011, 11:20 AM
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Why weren't chevy 307's and 305's used as performance engines?

When I grew up in the 80's, there were still LOTS and LOTS of 68-72 Chevelles and '68-'74 Novas around. I used to joke that you could walk over a busy highway overpass, be blindfolded, and drop a tennis ball over the overpass, and chances are you'd hit a Chevelle or a Nova! Even in the mid to late 80's....

Anyway, many of these cars came stock with 307's, and still had the 307 badges. In fact, my step-father owned a Chevelle with a 307, and I also had 2 other friends who owned Chevelles that came with 307's originally. Not to mention the people I knew who owned 307 equipped Novas.

However, when It came time to try and increase the performance of these cars, it seemed the first thing everyone did was to get rid of the 307, and replace it with anything from a 283-302-327-350, etc.

I asked why this was, and I was told by more than 1 person that the 307 was a completely different engine than the 283-327-350-400 gen 1 small block, and that it just wasnt any good for performance.

Later I learned that the 307 was in fact a member of that same gen 1 family, so why didnt people seem to like the 307?

Then we have the 305.......
I was also told by many of the same not-so-knowledgeable people that the 305 was also a different engine than the 350, etc., and wasnt much good for performance, even though it was used by GM as a standard equipment performance engine in the 80's-early 90's in several cars. However, many people still seemed to want to remove it and replace it with a 350.

Now, I can understand why someone would replace a smaller engine for a larger displacement engine, but that didnt seem to be the primary reason that people were replacing these 2 engines.... In fact, I met 2 different people who built 283's, and swore by them! Obviously a 283 is smaller than a 305 or 307, so why not use the 305 or 307 if its made from the same engine family?

There is also the 400 Chevy, and I know another guy who owned a '73 Nova who replaced its original engine with a modified 400, but it didnt last too long... The 400 supposedly has such a big bore that it effects coolant passages and wall thickness, which is bad for high horsepower purposes.
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