355 LT1 Dart Cylinder Head, Comp CamsCamshaft & Roller Rocker Upgrade - Top End

Part IV: Dart, Comp Cams And Racekrafters Help Us Calculate A 450+HP Formula For A Street-Going 355 LT1

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.

0903gmhtp_28_z 355_lt1_dart_cylinder_head_comp_cams_camshaft_roller_rocker_upgrade Dyno_results 28/29

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.

Sources

Comp Cams
Memphis, TN 38118
800-999-0853
http://www.compcams.com
Dart Machinery
Troy, MI 48084
248-362-1188
www.dartheads.com
RaceKrafters Automotive Machine, Inc.
Lancaster, PA 17601
717-399-8780
www.racekrafters.com
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