It's hard to believe it's been about 15 years since the "Three Musketeers" (Dennis Clark, Mike McCagh, and John McRae) collaborated with the "mad engineer" (me) to fulfill a line item on his bucket list - design a camshaft that really works.
Since I had already developed the 7000 rev "327 LT-1" configuration for SHP/FI 327s, I turned my attention to the 300 HP version, which is the most commonly installed engine of the 327 era. Some don't consider it a "real" Corvette engine because it was shared with the passenger car lines and lacks the dress-up features and lopey idle of the SHP/FI engines, but it has it's own desirable features like stump-pulling low end torque that works well with taller gearing for more relaxed freeway cruising and decent fuel consumption. In fact, for the way most of use these cars nowadays, it's probably the best configuration.
My thought was can it be configured to make L-79 type top end power and revs while maintaining the butter smooth 500 RPM idle, low end torque, and visual appearance of an OE 327/300 and pass a PV? I definitely thought it was possible!
The first operation is "head massaging" just like the "327 LT-1" configuration. Then it was a matter of finding the optimum valve timing to maximize torque bandwidth in the 1000-6000 RPM range and maintain the 500 rev smooth idle. I was hoping to use OE lobes, and it turned out there were two that were just about right. It was simply a matter of a little rearrangement.
After testing of the three prototype engines I wrote a "technical support paper", revised it in 2008, and posted it here back in 2018.
No more than a handful or two of these engines have been built since then. The most recent one was finished earlier this year and the performance results are documented in the following thread:
Another one is currently in the works, so I thought it was time to revise the paper again. It is attached to this thread, and there are links to more useful papers on the last page, and some words about configuring later base engines to this configuration.
They should all be a worthwhile reads for anyone contemplating a precision engine rebuild. In fact, 90+ percent of the difference in performance characteristics between the 327 LT-1 and Special 300 Horsepower configurations is the camshaft!
Duke
Since I had already developed the 7000 rev "327 LT-1" configuration for SHP/FI 327s, I turned my attention to the 300 HP version, which is the most commonly installed engine of the 327 era. Some don't consider it a "real" Corvette engine because it was shared with the passenger car lines and lacks the dress-up features and lopey idle of the SHP/FI engines, but it has it's own desirable features like stump-pulling low end torque that works well with taller gearing for more relaxed freeway cruising and decent fuel consumption. In fact, for the way most of use these cars nowadays, it's probably the best configuration.
My thought was can it be configured to make L-79 type top end power and revs while maintaining the butter smooth 500 RPM idle, low end torque, and visual appearance of an OE 327/300 and pass a PV? I definitely thought it was possible!
The first operation is "head massaging" just like the "327 LT-1" configuration. Then it was a matter of finding the optimum valve timing to maximize torque bandwidth in the 1000-6000 RPM range and maintain the 500 rev smooth idle. I was hoping to use OE lobes, and it turned out there were two that were just about right. It was simply a matter of a little rearrangement.
After testing of the three prototype engines I wrote a "technical support paper", revised it in 2008, and posted it here back in 2018.
No more than a handful or two of these engines have been built since then. The most recent one was finished earlier this year and the performance results are documented in the following thread:
Another one is currently in the works, so I thought it was time to revise the paper again. It is attached to this thread, and there are links to more useful papers on the last page, and some words about configuring later base engines to this configuration.
They should all be a worthwhile reads for anyone contemplating a precision engine rebuild. In fact, 90+ percent of the difference in performance characteristics between the 327 LT-1 and Special 300 Horsepower configurations is the camshaft!
Duke
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