[Formulajones]

Originally Posted by GRX

Great subject. Almost wish cell phone videos were as ubiquitous back then as now. Almost.

Back in the day one of the baddest street racer cars around here was my neighbor's 390 powered AMC javelin. Remember him spanking a lot of cars with it. Including some BBC cars and Pontiacs.

As said above, a large part of it was tuning. Another big one is production inconsistencies. How much casting shift? How closely did quality control monitor the machines? When blueprinting you can see how many variances there are. Of the muscle car era engines I have worked with Mopars were the worst offenders. Valve spring seat depths all over the place. Conn rods several grams off from each other. Indexing and stroke specs on some of the cranks was atrocious. Essentially had to 'unlock' the machine and align it with what was already there because fixing would take it far below bearing under-sizes. This is why you could have one Mopar that ran like a scalded dog, and another like a sick puppy. Same deal goes for other brands as well. Our Pontiacs included. Just not bad as others.

This is exactly why you see these cars today in Pure Stock putting up some astounding numbers at the strip. Fact is, back in the day they were pumping these cars out with a limited warranty. They weren't built to exacting tolerances.
I've rebuilt several virgin engines here that have all kinds of issues. Ran fine, but just not up to standards I like to see. Things like off on stroke, deck heights uneven, and a combination of the 2 things causing different compression ratios per cylinder, and nothing even close to advertised numbers. Stock rocker arms that aren't even close to their advertised ratios, it just goes on and on. Just correctly rebuilding these engines, with proper deck height, stroke, checking cam lift and rocker ratios, true compression ratios etc....you can find a lot of hidden HP in these things, and they are essentially, for all intensive purposes, still stock.