Don Terrill’s Speed-Talk

There was discussion a while back on S/T regarding a series of seminars by David Vizard: HTTPS://www.youtube.com/watch?v=Y_6qBG3XknM in which he mentioned the number 128 as being a crucial factor to spec out a really effective cam first time around. As I remember there were some who (understandably) began to doubt DV's engineering sanity.

Well, all has now been revealed in a two part cam selection article by him in the October and November 2015 issues of the highly respected UK Racetech magazine: http://www.racetechmag.com. When you read this you really will see how '128' is the most important number you can know about specing out a cam for a typical Detroit V8.

I have to wonder why the cam companies have not come up with this as a viable method toward specing out a cam that will produce more torque and power than would otherwise be the case. I've pesonally experienced the phenomenon mentioned in the article, wherin contacting different companies (or even the same one on a different day) elicted very different specs for the same application.

One example about 7 years ago really left me shaking my head. I'd specced out a cam for a friend's SBC Trans Am Corvette, based on trusted expert input plus many hours of Dynomation simulation. At 735 HP, the engine looked to be on track to attaining the expected power but the session ended early due to a number of mostly self-inflicted problems: The rods that had been relieved to clear the cam were put in the wrong cylinders, causing light but worrisome knocking and the Jesel cam gear bolts were under-torqued during an index change, leaving the cam and spark timing a little unpredictable. Upon teardown, we found major wear on a number of lobes; clearly the grind had broken through the case hardening. The (BIG cam company) rep offered a new shaft for free, but insisted his (very different) spec "would be worth 35 HP". Sure enough, 35 horses exited the engine!!

I'm not sure how copyright laws apply to reproducing such data, but perhaps David can now chime in with the '128' details.

I was hoping to read this, but it looks like the articles are not available online?

You can buy the back issues for $11.99 I think?

Looks like it would be a good article.

FYI, I just bought both $32.24 total including shipping.

I read them both and found them informative I think it would be good if the mag will allow David to post it or provide a link to the article.

MadBill wrote: but insisted his (very different) spec "would be worth 35 HP". Sure enough, 35 horses exited the engine!!

How did the specs differ? Did the RPM of peak HP drop?

Kinda weird how David posts in a thread regarding the epa deal, but doesn't in this one? lol

Given the terminally hopeless state of the US Patent Office nowadays, I should probably run in quickly and patent the number 128.

MrBo wrote:

MadBill wrote: but insisted his (very different) spec "would be worth 35 HP". Sure enough, 35 horses exited the engine!!

How did the specs differ? Did the RPM of peak HP drop?

Sorry, I didn't see the specs for the replacement cam. It was ~ 10 years ago and I don't remember how much lower it peaked with the second cam.

Warp Speed wrote:Kinda weird how David posts in a thread regarding the epa deal, but doesn't in this one? lol

I think we know what thats all about.

MadBill wrote:
I'm not sure how copyright laws apply to reproducing such data, but perhaps David can now chime in with the '128' details.

Discuss away, just don't copy and paste copyrighted material. You can always talk about anything you please (with a few restrictions around harming people), but you can't copy and paste someone else's words without their permission.

Copyright protects the actual written words exactly as they are written and reproduction of images not an idea re-presented in your our words or images you draw provided they are not exact copies. A patent protects an idea but only prevents production based on the idea, it does nothing to prevent discussion of the idea itself or building new patents on the idea but you still can't make your invention it uses someone else's patent and you don't have permission.

mk e wrote:

MadBill wrote:
I'm not sure how copyright laws apply to reproducing such data, but perhaps David can now chime in with the '128' details.

Discuss away, just don't copy and paste copyrighted material. You can always talk about anything you please (with a few restrictions around harming people), but you can't copy and paste someone else's words without their permission.

Copyright protects the actual written words exactly as they are written and reproduction of images not an idea re-presented in your our words or images you draw provided they are not exact copies. A patent protects an idea but only prevents production based on the idea, it does nothing to prevent discussion of the idea itself or building new patents on the idea but you still can't make your invention it uses someone else's patent and you don't have permission.

Agreed. But David has a further obligation to the publisher no doubt. Your comment would better apply to someone with knowledge of the content with freedom to comment and discuss.

Olefud wrote:
Agreed. But David has a further obligation to the publisher no doubt. Your comment would better apply to someone with knowledge of the content with freedom to comment and discuss.

yeah, I meant anyone who's read the article is free to explain what the heck this thread is about

I'm glad he laid out a range in the article. I've had success using the 128 deal on engines that we'd normally build with aftermarket heads that we'd normally use but I've found the math to be off a little on funky builds.

The most dramatic example was on an AMC inline 6. 128 called for a cam on basically a 106 (rounding the numbers here because I doubt a cam grinder will give you something on a 105.77, lol) but when I had the opportunity to run the engine through COS-Cams, it specced a 102 LSA.

At least now I know what numbers to fudge when dealing with funky engines with terrible low-lift flow.

As long as it is accurately quoted and not directly reproducing the whole for sale or profit, there's no restriction:

Under the "fair use" rule of copyright law, an author may make limited use of another author's work without asking permission. Fair use is based on the belief that the public is entitled to freely use portions of copyrighted materials for purposes of commentary and criticism. Subject to some general limitations, criticism and comment are usually deemed fair uses -- for example, quoting or excerpting a work in a review or criticism for purposes of illustration or comment.