The EngineQuest cylinder heads were the subject of an impressive development effort. Robin
The EQ heads on this particular engine were the subject of considerable development work at SKMFX. Robinson explains: “I got to work pretty extensively in the cylinder heads. I got away from the factory 8mm stem valves, and went to 11⁄32-inch because it opens up far more selection in off-the-shelf valves. I went with Manley Severe Duty intake valves in a 2.08-inch diameter, with a 5.250-inch length. A part of the puzzle that predicated how I built the heads was coming across a set of secondhand unused T&D rockers. I put the bedplate on the Magnum pedestals, and selected the valve length to best suit the geometry with the rockers. These EQ cylinder heads are nice to work with, having plenty of metal for porting. I put them on the CNC mill and wrote a program to open the bowl out to a venturi shape, and with this mod alone the port went to 273 cfm. I put the valve job on it and hand-blended the machine work, and then put it on the CNC again to open up the intake side of the port. After hand-finishing the port work and many trips from the cutting bench to the flow bench, I ended up with 300 cfm at .600-inch lift.”
A characteristic of the Magnum-style heads is outstanding exhaust flow. Robinson relates t
On the camshaft, the custom COMP hydraulic roller cam actually uses slightly less duration on the exhaust side than on the intake. Part of this is because of the very high exhaust flow from the EQ heads. “The exhaust side has very high flow; it can get to around the 200-cfm level with very little work. I found on the other EQ head builds and the W2 head builds I’ve done in the past, that I’m over-exhausting the engines. My VE numbers will be over 100 percent from the bottom of the pulls to the top, and the power doesn’t really correspond with those kinds of efficiency numbers, so I’m led to believe that I’m blowing everything out the exhaust. I took one stab at the camshaft, and I don’t think I was too far off the mark, since on my dyno the engine was producing over 510 lb-ft of torque at the peak.” The cam features 246/244 degrees duration, using the more aggressive COMP SPTK lobes on the intake side, and the milder HRR lobes on the exhaust. Lift is .648 inch with the 1.5:1 ratio rockers, while the lobe separation angle is 106 degrees. The cam was installed at an intake centerline angle of 102 degrees.
As run in the competition, the intake ports posted a peak flow of 300 cfm at .600-inch lif
The engine uses a Weiand X-celerator intake manifold, but Robinson tells us that he thinks there was room for improvement in the induction. “It was the only manifold I had at the time, and I figured I would just put it on if the output looks like it is within reason. I had the heads flowing around 300 cfm, and with the intake on it the intake port flow dropped to around 230 cfm. I experimented with custom runner extensions in the plenum, but they ended up hurting power everywhere. I actually cut them back out, and put in much more conservative extensions.” Topping the manifold is a Holley 750 HP. Robinson spoke highly of this unit: “What can I say about the Holley HPs? The 750 HP seems to be the one to buy if you want to have just a spectacular carburetor out of the box. I did not modify it; I just calibrated the air bleeds and jetting.”
Providing the air/fuel mixture is a Holley 750 HP-Series carb. Robinson tells us these are
Taking advantage of a production oddity, the engine is fitted with a factory Chrysler Lean-Burn distributor. These distributors featured no advance curve or vacuum advance. As Robinson puts it: “Coupling the locked-out production distributor with the programmable curve of a MSD 6AL2, is a match made in heaven.” Rounding out the engine package is a pair of Schoenfeld stepped headers with 1⅝- to 1¾-inch primary tubes. Up front, a CAT crankshaft damper handles the vibes, while a custom billet water pump housing crafted at SKMFX accepts a Moroso big-block Mopar electric water pump.
A Weiand 7545 single-plane intake manifold was heavily modified with porting. Robinson exp
Sandwiched between the carb and intake is a Wilson tapered spacer. Robinson finds this spa
An off-the-shelf set of Schoenfeld Sprint Car headers handles the exhaust. The headers fea