The Plan
Mancini Racing recently started to offer killer deals on CNC ported heads, so we decided to see how they would perform on our 505-inch short-block. To top things off, we contacted Edelbrock for one of their brand-new Super Victor intake manifolds with the 4500 carb flange. Staying with the hot street plan, we hooked up with Comp Cams to get one of their Xtreme Energy street roller camshafts. We also took this opportunity to try out a Reher-Morrison shear plate, the new valve cover gaskets from Moroso, and some trick new valvespring retainers from Comp Cams.

The Short-Block
Project 505 was originally built for the Modern Max Wedge article that ran in the August 2007 issue of Mopar Muscle. It is based on a thick-wall, '77 production 440 block with a 4.250-inch stroke crankshaft from 440Source, a set of 6.800-inch-long Chevy rods from SCAT, and forged pistons from Diamond Racing. Those of you with sharp memories will recall that this short-block had 13.5 compression in the Modern Max Wedge article, but for this round of tests the compression dropped down to 12.5:1 with the Mopar heads. The pistons have stayed the same since the Max Wedge buildup, but the Mopar heads have an 84cc chamber as compared to the 75cc chamber in the Indy heads, so the compression ratio dropped a point.

This motor has seen a lot of dyno duty over the last couple of years so we learned to leave the short-block dressed up in dyno friendly parts such as a deep oil pan with a dual line Milodon pump, an external oil filter, a Jesel belt drive, and an electric water pump. These parts are not necessarily what you would find on a hot street car, but it's nice to have the durability that these parts bring to the table when we're doing a lot of dyno testing.

The Jesel belt drive for the camshaft is an expensive upgrade over a conventional timing chain, but it sure makes life easy on the dyno when we need to change cams or adjust the cam timing. One other item that we've been using lately on our dyno engines is a Jesel belt driven distributor. Once again, this is a fairly expensive upgrade from a stock type distributor, but the central location provides great access and we don't need to wrestle with the distributor every time we pull the valve covers to inspect the valvetrain. The belt driven distributor does not have any advance mechanism, so we're running a flat timing curve. As soon as the engine fires up, it goes straight to full advance and stays there throughout the entire rpm range. One thing we have noticed with this setup is that the timing is rock solid when checked with a timing light.

Headed In The Right Direction
The Mancini Racing-supplied heads are basically an aluminum version of the original 915 cylinder head with an improved port design for much better flow. These heads have a closed 84cc combustion chamber with a large quench area, and the valve diameters have been enlarged to 2.14/1.81 inches respectively. To produce these heads, Mancini Racing starts off with a Mopar Performance PN P5153524, which they then send out to Modern Cylinder Head for full CNC porting. The CNC porting increases the airflow to 325 cfm at .600-inch lift on the intake side, and 230 cfm on the exhaust side. These heads have a straight spark plug location that is similar to a stock cast-iron head rather than the angled plug that most aftermarket heads have. The straight plug design fits many header designs better than the angled plug heads since many headers were originally designed for stock heads.