Originally Posted by Conanski
Concerning your other questions...
There is an adapter to put a 5.0HO upper on a 5.8 lower, but that intake is restritive on a 5.0 with some mild mods, so I don't see it helping a 351.
The 5.0 truck intake actually has much larger runners than the 5.8, same length but bigger cross section.. me thinks Ford goofed with the castings and got them reversed. A 5.0 upper won't seal with the 5.8 lower, and it's pointless anyway, runners will be no shorter and airflow will be a mess. One guy here dyno'd a 5.0HO motor with both the 5.0 truck intake and the HO intake and the truck intake made more HP.. would seem to indicate it flows better.
Instead of starting a new thread that pertains to some of the same issues, I decided to drag this old thread out of retirement so please bear with me. I also would like to get some additional power out of my doggy roller 351W. In the post I quoted, you said that a 5.0 upper won't seal with a 5.8 lower. Are you talking about a 5.0HO or 5.0 truck upper? I was wondering if a 5.0 truck upper will bolt on to a 5.8 lower, my thinking being is that I could port the lower to match the 5.0 truck upper if it will bolt on. Any thoughts? Thanks.