Finally got a dyno pull started at 1000

[Duke W.]

I've been harping about this for years, but usually the pulls start at 3000-3500 even though these engines spend most of their life in the lower half of the rev range.

Subject engine is a '64 327/300 rebuilt to the Special 300 HP configuration with a McCagh Special camshaft tested on a Dynojet inertia type chassis dynamometer.

My basic criterion for a good high performance road engine is no less than 80 percent of peak torque at 2000.

How about 90 percent at 1000 along with L-79 top end power and revs with a 500 @ 18" butter smooth idle.

I'll have a full report later this week after I finish analyzing all the data.

Duke

[Michael L.]

Re: Finally got a dyno pull started at 1000

Nice! I've noticed the very late start to dyno pull data on several engines I've had dyno'd and also wondered why they don't start recording power earlier. Not sure if It's a software issue or just the choice of the dyno operator.

Mike

[Bill B.]

Re: Finally got a dyno pull started at 1000

Duke,

You may want to patent that combo that gets 90% at 1,000 and yet, have the top end power of that L-79!

Sometimes such results are from methodical engineering, and sometimes trial and error. Whichever, or combo, you've got something there!

Awaiting the final results with baited breath!

PS - I betcha the Brake Specific Fuel Consumption is outstanding with that combo as well!

[Duke W.]

Re: Finally got a dyno pull started at 1000

Duke,

You may want to patent that combo that gets 90% at 1,000 and yet, have the top end power of that L-79!

Sometimes such results are from methodical engineering, and sometimes trial and error. Whichever, or combo, you've got something there!

Awaiting the final results with baited breath!

PS - I betcha the Brake Specific Fuel Consumption is outstanding with that combo as well!

The McCagh Special was the second of two camshafts I designed circa 2008, and I documented the project in "A Tale of Two Camshafts" that was published in The Corvette Restorer in 2010. It's also on the Web... easy search.

Available data at the time indicated the McCagh Special offered greater torque bandwidth, so that's the one I recommend when answering inquires about how to obtain one.

Several friends suggested I go into business selling them, but I figured the market was narrow and I didn't want to turn a hobby into a business. I only requested that prospective users contact me so I could verify that they understood the unique configuration requirements. Once I was assured that they understood the parameters I gave them the Crane part number and contact information.

Crane is gone now - purchesed by Comp, and I don't know what happened to their documentation and tooling, but since both inlet and exhaust lobes are from Chevrolet OE cams, any grinder who has lobe masters can grind this cam today.

Two of the first design were built and tested, and no more than a handful of McCagh Specials have been ground. I know of one installed in a C3, but the owner declined testing. One was bought for a future rebuild, and I don't know the status, and one was procured by an owner who never contacted me. Apparently he contacted Crane and they figured out what he wanted. Any more? I don't know.

I think most of the users were experienced DIYers and after reading the article figured I was onto something and were willing to spend the time and/or money to do the required head massaging.

I had several inquiries from Corvette owner's who were having their engine rebuilt by some "engine builder" who recommended XYZ camshaft and they all appeared to not know much about engine performance. From other experiences I also knew that if they were going to pay hundreds if not several thousand dollars to some engine builder that's who they would listen to rather and a guy with free advice. I didn't want this cam to fall into the wrong hands... someone who would not properly follow the other configuration requirements and end up with a dog.

Chassis dyno tests don't give BSFC, but they do give A/F ratio, and I was impressed how well the old 3721SB AFB delivered a quite consistent WOT A/F ratio in the proper range over the entire rev range.

A cruise A/F, surprisingly, was almost as rich, and maybe it can be leaned out with just a metering rod change.

Duke