: Rebuild '76 500 w/ '70 472

10-25-04, 10:24 AM
I'm in the middle of a '76 500 rebuild, I want to convert the build over to the new '70 472 that I bought. Everything between the two motors are the same except the heads, the crank and the pistons right? Are the connecting rods different, what about the head gaskets? It's the difference between my '76 heads and the '70 heads that makes the horsepower difference?

lux hauler
10-25-04, 04:17 PM
The horsepower ratings are very deceiving. The '70 engine was rated as gross horsepower. The '76 was rated as net. There really wasn't as much difference as it appears......compression, the rating system used, and a less efficiant design and tuning all contribute to the lower numbers.
The heads from '70 were a smaller chamber design. That, along with a different piston made the compression higher than the later engines.
The crank and pistons were the only things that were different between a 500 and a 472 of the same years.
So, you can bolt the '70 472 heads to the 500 bottom end and it will work.....you just have to be careful of the compression. Early heads on a late engine (late piston design) will net you 12.5:1 compression. With that kind of compression, you'll have to run racing fuel.$$$$
There are pistons available that will work with the early, small chamber heads, that will give you around 10:1 compression.