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Is this a Dream or–is that really my LS7?

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CAC Does the Corvette Engine Building Experience - Page 8 of 10

by Hib Halverson
© September 2012
No use without permission, All Rights Reserved

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Click on the images for expanded views – it's much easier on the eyes. 

The next step was to put the valvetrain together. As I stood next to my engine with a fist full of pushrods, I thought about something Jordan Lee, GM's Global Chief Engineer for Small Block Engines, once told me. "Our philosophy is not to add technology for technology's sake. If technology is really not a performance benefit, we won't implement it."

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Image:  Mark Kelly/GM Powertrain

One feature which contributes to the "LS7 Mystique" is the engine makes 505-hp and turns 7100 rpm with (or, perhaps, in spite of) the simplicity of pushrod operated valves.

As I dropped the pushrods in place, I considered: 505-hp, 7100 rpm and no guzzler tax. Overhead cams? We don't need no overhead cams or four valves-per-cylinder. Heck, we don't even need three. Back in the days when rumors were running wild about what would follow the LS6, there was talk about a six-four with a three valve head–two intakes and one exhaust. GM actually patented the system back about 2002 and there was even an article SAE's "Automotive Engineering" magazine covering GM's experiments with it. In the end, the two-valve LS7 head was so good, GM scrapped the 3-valve idea.

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Image:  Mark Kelly/GM Powertrain

The rocker bolts get tightened in two groups of eight. The first group is done with the engine at TDC #1 and the second group is done with the engine at TDC #6. You engage each bolt head with the socket on the power wrench and squeeze the trigger until the green indicator light comes on.
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Image:  Mark Kelly/GM Powertrain

Once the bolts are tight, every rocker gets generous squirt of oil to prelube trunnion bearing and the pushrod seat.

One by one, I dropped the investment cast steel rocker arms in place. To save time, the rocker bolts are tightened in two groups of eight. Delrin racks go on the heads to hold the rockers in place while the rocker bolts are tightened with one of those torque angle sensing power wrenches. The racks are color coded by rocker arm group, either green or yellow. You turn the engine, tighten all the "green" rockers, then turn the engine, again, and tighten all the yellow ones–so easy, even tech writers can do it.

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Image:  Mark Kelly/GM Powertrain

The harmonic damper going on means we're in the homestretch of getting this engine built.
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Image:  Mark Kelly/GM Powertrain

I always thought putting those coils on the rocker covers made Gen 3/4 engines look ugly. You can put the coolest-looking carbon fiber covers on the engine but once you add those coils, you still have an unattractive sight. You'd think, after 15 years of working on Gen3/4 engines, I'd have gotten used to that–but I haven't.
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Image:  Mark Kelly/GM Powertrain

I remember the first time I saw an intake manifold made of glass-reinforced Nylon–I thought: WTF? But, I've become a believer mainly because they are lighter and run cooler.
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Image:  Mark Kelly/GM Powertrain

This large device is for tightening only one fastener on the engine, the harmonic balancer bolt. The spec. is 80-Nm plus 200°–seriously tight. I 'spose that's why the power wrench is so big.
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