While we continued to grapple with the changes required to accomplish the automotive equivalent of installing a square peg in a round hole, Pete Incaudo and Anthony Spensieri of VMax Motorsports were reworking the engine's cylinder heads. Pete has been porting cylinder heads for more years than either one of us care to remember (dating back to the '70s, when his Cylinder Heads America company supplied small-block cylinder heads to the majority of winning and record-setting drag racers). Pete was also first to recognize the potential of CNC-porting for street applications, and he has an unrivaled understanding of the way air flows through a cylinder head. That understanding enables him to develop port designs that deliver optimum flow characteristics while meeting specific cost limitations.
We installed the springs at...
We installed the springs at the recommended height of 1.800-inch, which provides a seat pressure of 130 pounds and an open pressure of 318 pounds at 0.600-inch lift.
Valve size obviously has a...
Valve size obviously has a significant impact on air flow capacity, so Incaudo installed LS6 2.00-inch intake and 1.550-inch exhaust valves. Had these not been available at such an attractive price, we would have used REV stainless valves. They are reasonably priced and have excellent flow characteristics and durability.
Sure, we could have reused...
Sure, we could have reused the original timing set, but that might well have been a case of jumping over dollar bills to pick up pennies. Although timing chains and sprockets rarely fail, they do wear, and since the original parts had already run over 80,000 miles, reinstalling them would have compromised performance. Instead, we selected a high-quality, adjustable timing set from Comp Cams (PN 3153KT).
Considering our $15,000 total budget, cost considerations aren't taken lightly. Certainly, a pair of fully CNC-ported heads will provide higher air flow capacity and, ultimately, more horsepower, but they'll also cost a good bit more. Our challenge to Pete was to come up with a maximum power/minimum cost combination. And that's precisely what he did.
Pete's budget-conscious modifications of our 5.3-liter head castings incorporated hand porting and blending the valve bowl area and short turn radius (which is the section of the port that has the greatest influence on flow). After the port work was completed, Anthony attacked the castings with his array of seat, guide, and valve machines. Through his extensive background in race engine head and block preparation, Anthony has developed a number of machining procedures that assure maximum precision. In developing race-winning components for classes in which allowable engine modifications are limited, he found that power output and durability are increased when valve seats and guides are machined to specific precision and consistency standards. In years past, that type of work meant relatively high costs because of the time involved. But with the new high-tech machinery that has become available during the past few years, that's no longer the case because operations that formerly required multiple steps can now be completed in a single step. That makes them ideal for limited-budget performance street engines.
Although a deep oil pan is...
Although a deep oil pan is desirable, using such a pan to excavate driveways leads to rapid oil loss. That's just what will happen if one is installed on an engine that resides in a C4's engine compartment. The truck pan is so deep it hangs well below the crossmember.
This F-body oil pan is considerably...
This F-body oil pan is considerably shorter and eliminates pan-to-ground interference issues. In addition to the pan, the oil pickup and windage tray must also be changed.
Combined with our special "C4orce-grind" camshaft that was ground by Comp Cams, the modified heads should pump up the horsepower of our $700 5.3-liter LSx to about 335-or about 90 more than the original 5.7-liter old-school TPI engine. Sound good? It does to us, and we'll have more details next month.
| DIFFICULTY INDEX ::: NNNN |
|ANYONE'S PROJECT | no tools required || N |
|BEGINNER | basic tools || NN |
|EXPERIENCED | special tools || NNN |
|ACCOMPLISHED | special tools and outside help || NNNN |
|PROFESSIONALS ONLY | send this work out || NNNNN |