[markjohnson]

The #077 over-the-counter aluminum cylinder head is much superior to the factory installed #074 production head. That giant round exhaust port makes for a poor intake-to-exhaust port ratio. The #077 head has a beautiful D-shaped exhaust port with a cast in vane on the port floor. It also has a little bit smaller intake port to try to compensate for the big blocks' infamous 4 good/4 bad intake ports. Both heads do tend to suffer from valve guides that like to move around unless they are pinned at the valve spring seat. People like to pay more money for the #074 head because it is considered more correct for an aluminum head L-88.