The iron EQ cylinder heads are much improved over a factory Mopar Magnum head right out of
To make them work to their potential, the added cubic inches of the stroker short-block rely on the correct team of complementary parts. Robinson tells us, "The cylinder heads have the most important effect on the overall build. I have put these kinds of stroker engines together with stock Mopar J-heads, and you'll only see 460 hp and they will be all done at 5,300 rpm. This might be appropriate for a pickup truck or a large Mopar C-Body, but it isn't going to make it as a performance engine in a lightweight A-body." As cylinder heads also play a major role in the overall cost of the engine project, Robinson sought to explore the potential of EngineQuest's budget-oriented iron heads. Robinson continues, "The basic cost of the EQ heads is a real bargain, and then there are the related cost savings in the headers, intake, and valvetrain with the OEM layout."
While the heads offer excellent performance in their stock configuration, especially at stock displacement, the heads become more critical on larger stroker engines. To really dig into the potential of these castings, Robinson embarked on a development and modification program. "I was shooting for overall port volume and cross-section, knowing that with 417 ci I was going to need every bit of real estate I could get. The main focus was on the intake port; I ended up lowering the floor substantially, and managed to open up the runner in the pushrod area to 2.350 square inches. This could be expanded upon by sleeving the pushrod holes, but this would be getting away from the overall theme of the modifications." The effort resulted in intake flow topping the 300-cfm mark.
As with the cylinder heads, SKMFX worked their porting magic to optimize the airflow from
With ample cylinder head flow on tap from the modified iron EngineQuest heads, the inducti
The FAST EZ throttle body is a self-contained TBI unit featuring four injectors on a 4150-
Even the best cylinder heads will perform far under their potential if the induction system puts a cork in the flow stream. Here Robinson went to work on Edelbrock's new Super Victor intake for the Mopar small-block. As Robinson explains, "I was pretty excited to use the Super Victor intake. I worked the plenum pretty extensively, again with an eye toward overall cross-section based upon the cubic-inch and rpm range of the engine. I was looking for a happy medium between cross-section and runner length. I feel there is room for improvement there still."
Tuning the FAST TBI is assisted through a handheld tuning module. The software is designed
Bolted to the big Edelbrock single-plane intake manifold is a 1,000-cfm FAST EZ-EFI throttle-body injection system. Robinson had good things to say about this system, "The EZ did what it was supposed to do, as far as being a bolt-on carburetor replacement with basic tuning parameters. It did perform quite well, with very few issues. On initial fire up I used one of my go-to carburetors and saw almost 570 hp with the carb. I moved on from there thinking that if the EFI could match that or come close to that output I would be happy.
As it turned out the FAST EFI actually made more power at peak. From what I could determine the fuel distribution was very good. This whole engine package is aimed at the average guy who wants to put something relatively simple together without the complexity of a port injection system. The throttle-body injection from FAST fit this role perfectly."
Working in conjunction with the FAST fuel system is a programmable ignition system from MSD. With the advance requirements working electronically, there was no longer a need for a distributor with any type of advance provisions. Robinson went with a factory Chrysler distributor from their infamous "lean-burn" ignition system, which features the triggering function of the magnetic pickup only. This unusual arrangement functioned as though the components were designed to work together and performed without fail.
While the induction and heads are key players in the flow system, the exhaust completes th
Circulating the coolant is an OEM replacement-style beltdriven water pump. The use of a se
Needing an ignition trigger signal only, SKMFX used a low-buck junkyard “Lean-Burn” factor
The final key ingredient to this power package was the cam and related valvetrain. Here Robinson opted for a hydraulic roller, using a custom cam from COMP. Robinson reveals, "The cost from COMP for a custom cam is comparable to a shelf cam, so a custom cam is definitely the way to go. You can also specify a cast core, so you remove the requirement for a bronze distributor drive, which is a benefit for the street. I don't like having a consumable part in an engine. A big plus with the hydraulic roller is not having to fear wiping out a flat-tappet lobe. I wouldn't use a hydraulic roller with an offset rocker head like a W2. I find they don't get along very well, and it is just not a good combination. They work very well, however, on a non-offset rocker head like these iron EngineQuests. I wanted .650-plus lift on the intake side and used COMP's HHR lobes, but used lobes that are much slower on the exhaust. With the cubic inches and cylinder head combination I thought the engine could benefit from a little wider lobe separation to broaden the power curve."
The supporting components in the valvetrain are no area to skimp if you're looking to make the most of a camshaft and have it endure over the long haul. Here the bulletproof T&D rockers certainly meet the quality requirement, though Robinson suggests that a conventional rocker arrangement can also provide outstanding results. Robinson stresses high strength and quality valvetrain parts: "I am in the camp that weight takes a back seat to stability and rigidity in the valvetrain. I really like these Scorpion lifters; they are just fantastic quality parts, made in the United States, for a very good price."
So, in summary this engine package represents the common man's Mopar stroker—a very ordinary 360 production block filled with regular street stroker internal parts. With the iron EQ Magnum-style heads, hydraulic roller cam, cast Edelbrock manifold, and street-style throttle-body injection, it might be your average mid 400hp street mill. The dyno chart, however, proves otherwise, with the curve peaking at the 6,000-rpm mark, producing stout output in the upper 500s. A key ingredient is the custom work to the heads and induction, helping move air through the big small-block. While these kinds of numbers might represent the upper realm of output possible from such a basic parts list, it also serves as a benchmark of what could be done when that basic parts list is fortified with sensible engine-building know-how and an extra helping of careful craftsmanship.
The ignition signal from the stock distributor is routed to an MSD ignition, featuring the
Looking at power output, what do you think is a good number from a factory-derived Mopar u
At the 2012 AMSOIL Engine Masters Challenge, SKMFX team members Joe Rutters and Jesse Robi