Merc HP450 motor ?
 

Does anyone know any iformation about the HP450's. I think they are pre 1997. I was told that they were the merc motors before the HP500's came out, and were dressed in blue as the 500's are.

What are these motors exactly, and what did merc do for the extra 50hp?

HP450 was a 454 block with a roller cam. Didn't seem to be very sucessful.
Gary

like Gary said HP450 was basicly a HP500 with 454inchs same intake and exhaust with a hydralic rollercam, most people either opted for the 500hp or for alot less money the 502 mag which was rated at 420 at the time
later

It was very similar to the 454-420hp of the mid 80's but with a roller cam and Gil manifolds.

The 450 HP was introduced in 1994 about the same time as the 465 HP which was based on the 502 block. Both motors were hand built by Mercury's high performance division prior to the 500 HP. The 450 actually produced 460 horsepower on the dyno and is identical to the 500 HP except for the 454 block.

I ran a pair of these motors in a 31 Sonic and was really happy with the performance and reliability.