Car Craft
Click here to find out more!

LS Engine Build - The Garage-Built LS Stroker, Part II

Last Month's Homebuilt 404ci LS Engine Is Now Making Noise Testing Four Different Cylinder Heads On The Garage-Built LS Stroker, Part II

By , Photography by

What We Learned
The biggest surprise of the day was the torque improvement with the larger cylinder heads. When we originally tested the L92 heads on the 6.0L engine (May '07), these big castings killed the torque. But when we bolted these same heads to the 404ci engine, the torque exceeded that of even the WCRCH-ported 6.0L heads. Note how the average torque for both big port heads exceeds even the ported cathedral head by no less than 4 lb-ft. While we didn't achieve our 575hp goal, we did see an amazing 81 peak-to-peak horsepower improvement over the stock 6.0L heads.

While the CNC-ported L92 heads at first glance don't appear to be worth the additional cost over the stock L92 castings, we didn't really give these heads a chance to succeed. We would need to add a camshaft with another 6 to 8 degrees of duration and valve lift upward of 0.670 inch to take full advantage of what these heads offer. However, a bigger cam would definitely hurt the torque and make street driveability more of a compromise. One solution would be to improve the exhaust port flow on the stock L92 heads. The exhaust flow numbers on the WCRCH-ported 6.0L heads already outflow the CNC-ported L92 heads, and the L92 stock exhaust ports are supposed to be better than the stock 6.0L versions. It's a good bet that a stronger exhaust port would allow the engine to make more peak power without sacrificing the torque, and we'd have more horsepower without having to spend big money on expensive heads.

After the test, we dug a little deeper in the Comp Cams catalog and discovered a 281LRR HR13 cam that uses a 231-degrees-at-0.050 intake but adds a much longer duration exhaust at 247 degrees at 0.050 with 0.617/0.624-inch lift. This cam would probably carry the power out another couple hundred rpm and improve power at the peak. If you are considering replicating our combination, this is the cam we'd choose.

Finally, to put our 560 hp in perspective, we plugged the power into the Quarter Jr. dragstrip simulation program using our 3,200-pound Orange Peel '66 Chevelle running 3.55 gears and a 200-4R trans. The program spit out a low-11-second pass at 122 mph, assuming we could actually harness all this power. Sounds like fun.

Parts List
Description PN Source Price
Edelbrock Victor Jr., L92 28457 Jegs $349.99
Kwik alternator kit, Camaro K10194 Kwik Performance $167.00
GMPP L92 stock heads, pair 12582713 Scoggin-Dickey $899.90
GMPP L92 CNC heads, pair 88958698 Scoggin-Dickey $1,099.90
GMPP racing lifters 88958689 Scoggin-Dickey $226.85
L92 rocker, intake (8) 12569167 Scoggin-Dickey $95.84
L92 rocker, exhaust (8) 10214664 Scoggin-Dickey $98.80
L92 rocker support (2) 12600936 Scoggin-Dickey $15.92
Rocker arm bolt (16) 12560961 Scoggin-Dickey $72.80
Comp 281HR hydraulic roller 54-428-11 Summit Racing $354.75
Comp 277LR hydraulic roller 54-458-11 Summit Racing $396.95
Comp 281LRRHR13 roller 54-469-11 Summit Racing $396.95
Comp valvesprings 26918 Summit Racing $174.95
Comp retainers, steel 1772-16 Summit Racing $153.95
Comp pushrods, Hi-Tech 7955-16 Summit Racing $115.75
Edelbrock Victor Jr., LS1 29087 Summit Racing $269.75
Holley carburetor, 950 cfm 0-80496-1 Summit Racing $714.95
Edelbrock Victor Jr., LS1 29087 Summit Racing $269.75
Edelbrock headers, LS1 65073 Summit Racing $519.95
Autolite race plugs AR474 Summit Racing $21.52
MSD truck plug wires 32829 Summit Racing $68.95
Wilson tapered spacer, 1 1/2 004130 Summit Racing $178.95
ARP metric studs 400-8034 Summit Racing $151.95
WCRCH ported 6.0L head WCCH-6.0L West Coast RCH $1,575.00*
*Requires core-$1,865.00 outright with valves and springs
SOURCES
Scoggin-Dickey Parts Center
5901 Spur 327
Lubbock
TX  79424
800-456-0211
http://www.sdparts.com
Rock Auto
6680 Odana Road
Madison
WI  53719
866-762-5288
http://www.rockauto.com
Summit Racing
Akron
OH
800-230-3030
330-630-0240
http://www.summitracing.com/
Mahle Motorsports
Fletcher
NC
888-255-1942
http://www.mahlemotorsports.com
Chevrolet Performance Parts
P.O. Box 33170
Detroit
MI  48232
800-577-6888
http://www.gmperformanceparts.co
m
West Coast Racing Cylinder Heads
Reseda
CA
818-705-5454
www.proheads.com
Kwik Performance
Springfield
MO
417-955-1467
www.kwikperf.com
Wilson Manifolds
Ft. Lauderdale
FL
954-771-6216
http://www.wilsonmanifolds.com
Enjoyed this Post? Subscribe to our RSS Feed, or use your favorite social media to recommend us to friends and colleagues!
0 comments
Car Craft