The EQ heads showed good flow, good port velocity, and good swirl-all the ingredients for
The late-model (1993) roller-cammed short-block was stripped to the bare block and, together with our DSS pistons, taken over to T&L Engines in Stanfield, North Carolina. Here, we asked T&L boss Lloyd McLeary to furnish a cost-effective, nitrous-capable, balanced rotating assembly for our build that incorporates our DSS test pistons. We also needed to prep the block as per their budget custom crate motors. Normally they would supply a short-block built up with the customer's choice of cam installed and timed in. In this instance, we planned on doing the assembly in our studio/workshop, as it was far more convenient for the photography required. What we got back from T&L a couple of weeks later was a bored block, honed/decked deck plate, align-honed mains, detailed casting, and finally, a primered and finished block in engine enamel. Along with this was a Scat one-piece rear main seal cast steel crank (PN 10526) and a set of Scat's least expensive race rods (these are proving really tough pieces for something as light as they are; PN 2-ICR6000-7/16). Along with this, a Professional Products SFI certified race crank damper (PN 9000) was used. Lloyd also recommended an ARP crank bolt to maximize the crank and damper interaction.
As with many times in the past, we built a successful high-rpm roller valvetrain around a
The cam chosen for the job was a Comp XR282HR Xtreme Energy hydraulic roller. This had 282 degrees of off-the-seat duration on the intake and 288 on the exhaust. Duration at 0.050 was 230/236. Timed in at 6 degrees of advance, this cam makes a great middle-of-the-road choice between no nitrous and all nitrous cam. Normally, this would be driven by a simple double-row roller chain with a multi-keyway sprocket to get the timing required. In our case, a fully adjustable Comp timing set was used so we could make cam timing adjustments and cam changes in a speedy fashion.
The Cylinder Heads
The Engine Quest EQ23 heads we intended to use are the 50cc chamber race heads that have been doing very well in IMCA oval track racing to the extent they have won a number of championships. The fact that a lot of these oval tracks have a tight turn and a long straight means the heads have to be able to pull off a corner at relatively low rpm and wind all the way up to over 7,500 rpm toward the end of the straight. With a Comp Xtreme Energy hydraulic roller of 288 and 294 degrees of of-the-seat duration on a 108 LCA, from a 10.3:1 CR we have seen open exhaust 350, 470hp, and 445 lb-ft of torque with out-of-the-box EQ23s. The plan here is to drop 8 degrees of duration and spread the LCA by 2 degrees, add a pair of Flowmaster mufflers, and then see if the head porting will bring back the output to about where we were with the bigger cam and open exhaust but with far more streetablility.
Here is our Zex perimeter spray nitrous plate in position. Note that the opening at the ma
To establish the viability of successfully porting these heads with no previous experience, I had mechanical engineering/motorsports student Dusty Kennett port the heads. The only instructions were to skinny the guide bosses, blend the cast surfaces smoothly into the machined ones, and smooth out the rest of the port with coarse (80-grit) emery rolls. It took Dusty about 20 hours of cautious work the first time around, but the results were well worth it, as can be seen from the nearby flow tests. For the record, an experienced head porter could probably get this done in less than eight hours.
Intake flow improved from about 0.200 inch up, and at the intake valve lift our valvetrain would deliver (0.544 inch), the flow was about 8 cfm up on that produced by the as-cast port at 0.700-inch lift. The exhaust really picked up from 0.100-inch lift on up. This makes the head very nitrous friendly, as any nitrous application needs far more exhaust flow than does a regular nitrous application. As far as port velocity is concerned, these nominally 200cc intake and 60cc exhaust ports only increase in volume by 4cc and 3cc, respectively. For rockers, we used a set of Comp 1.6 aluminum roller items. If the motor spec had been for a non-nitrous application, there would have been a ratio split between intake and exhaust on this engine. Instead of 1.6s all around, it would have been 1.5:1 on the exhaust. This would have improved low-speed torque to the tune of 10 or so lb-ft and given an even slower idle capability.