The Edelbrock heads and cam combo achieved great torque, but it was apparent that a larger cam, at the very least, was needed to achieve our goal of over 450 ponies in an effort to keep up with our LS1 brethren. But to make good power naturally aspirated, we couldn't simply slap a few random parts together and call it good. Dart's Platinum Pro1 LT1 180cc heads were relatively new and untested, yet looked to be a formidable cylinder head for smaller cube motors. Dart's flow numbers had it on par with some of the best small runner CNC-ported stock castings and even some 195cc aftermarket castings. When we decided to give these $1,080 (bare) beauties a whirl, a call was placed to COMP Cams for its recommendations for a slightly aggressive street roller that would match the heads. After going back and forth a few times, it was decided that a custom grind 224/230-duration XFI roller should pair well and have good street manners. Naturally we would also have to use COMP's complementing 918 beehive valve springs (p/n 26918-16), to eliminate the valve float we were getting with the previous double springs, R-series lifters (p/n 875-16) and 1.6 ratio Pro Magnum roller rockers (p/n 1318-16). Follow along as we head back to RaceKrafters in Lancaster, PA to ring the last ounces of power out of our top-ended LT1.

DART PRO1 LT1 HEAD FLOW (CFM)*
Inch Lift Intake Exhaust
.100 71 69
.200 139 102
.300 190 136
.400 231 158
.500 254 175
.600 263 186
*Tested using SuperFlow SF-1020 flow bench with 28
inches of water and 4.030-inch bore.
Peak HP 459.4@6100rpm
Peak TQ 422.7@5200rpm
Avg HP 326.66
Avg TQ 401.16

Once we bumped up the fuel pressure to near stock (around 55-pounds), the 24 lb/hr injectors were at 84 percent duty cycle which is optimum for proper atomization. The new combination seemed to like higher rpm and 12.9 to 13.1 air/fuel, and with a few adjustments we were just shy of 460 hp. Bob and Craig both speculated that a tighter lobe separation might have prevented the dip in torque, but idle quality might have taken a nosedive. In any event, we were all happy with the results, which brought about the conclusion to this series. But that doesn't mean you've seen the last of this motor.

SOURCE
COMP Cams RaceKrafters Automotive Machine, Inc.
1140 Dillerville Rd
Lancaster
PA  17601
7-17/-399-8780
www.racekrafters.com
Dart Machinery
353 Oliver St.
Troy
MI  48084
248-362-1188
www.dartheads.com
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