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Old 12-02-2016, 10:26 PM
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Question Anyone familiar with David Vizard methods?

I'm helping a buddy build a sleeper motor (383, 11.2:1 AFR 210 eliminators) and I am studying the David Vizard method of cam design. We've chosen the overlap of 85 and the LSA comes out to 107 so that means a 243 x 243 duration and .638" lift with 1.6:1 rockers. BUT!!!!!! I cannot find ANY information on what he wants for ICL. Would I adjust the ICL to achieve a decent DCR, or what? His books and info look solid and his methods look interesting, but I need to know what to tell the cam grinder.

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Old 12-03-2016, 08:28 AM
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Greg,

With those cam specs, there'll be nothing "sleeper" about it. That baby will thump! Have you run those specs thru a dynamic compression calculator yet? That's more cam than I'm running in my 416" LS3 and mine's a solid roller...

Russ
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Old 12-03-2016, 09:04 AM
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Quote:
Originally Posted by S10xGN View Post
Greg,

With those cam specs, there'll be nothing "sleeper" about it. That baby will thump! Have you run those specs thru a dynamic compression calculator yet? That's more cam than I'm running in my 416" LS3 and mine's a solid roller...

Russ
Yeah, bad choice of words. I can't run thru a calculator until I get some timing events. That's the problem. I have no idea when he wants the intake to close. I can't seem to find that info. I know the guy has won every HP competition he's entered, and he's been designing cams this way for many many years. I've used his equations to come up with these figures but there is no mention of ICL. My GUESS is that he would want a 108 or higher ICL to keep the DCR down, but I'm not sure. And he wants $150.00 to design a cam, so maybe this is his secret thing. I don't know.

Here is how it works:
First, choose the overlap based upon the intended use Then use a bunch of math to come up with the LSA. After that, more math tells you what the advertised duration will be.
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Old 12-03-2016, 09:10 AM
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Call Cammotion and talk to Kip, he spec'ed my cam. Pretty sure he'll give you free advice over the phone...

Russ
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Old 12-03-2016, 09:15 AM
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Yeah, I could do that. I just hate to be "that guy" that calls looking for free advice from a person who makes their living on selling that advice. I know how I used to feel when everyone would call me for free advice about their golf cars.
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Old 12-03-2016, 10:03 AM
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Use this : Dynamic CR

The calculator is at the bottom of the page. Once you download the calculator you can go to page two (second tab) and enter that info 1st to find all of your cam events.

X2 - no sleeper about it. Tune it on 106+ octane, then drop out 5 degrees and retune it - that would be my plan.

EDIT : hit us with the rest of the build, don't keep us in suspense
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Old 12-03-2016, 10:14 AM
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Thanx, Nailhead. I'll give that a look!


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Old 12-03-2016, 10:30 AM
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Quote:
Originally Posted by Greg T View Post
I'm helping a buddy build a sleeper motor (383, 11.2:1 AFR 210 eliminators) and I am studying the David Vizard method of cam design. We've chosen the overlap of 85 and the LSA comes out to 107 so that means a 243 x 243 duration and .638" lift with 1.6:1 rockers. BUT!!!!!! I cannot find ANY information on what he wants for ICL. Would I adjust the ICL to achieve a decent DCR, or what? His books and info look solid and his methods look interesting, but I need to know what to tell the cam grinder.
If you are using his 128 method I believe he assumes the typical +4. I think he touches on it on one of the million page threads on Speedtalk on this subject.
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Old 12-03-2016, 11:29 AM
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Quote:
Originally Posted by TommyK View Post
If you are using his 128 method I believe he assumes the typical +4. I think he touches on it on one of the million page threads on Speedtalk on this subject.
Yeah, the 128 method which gives me everything I need BUT the ICL.

64Nailhead: Something isn't right with that calculator. When I enter all the numbers , as a test, from my current cam card, it tells me my intake closes at 75. My cam card says 50
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Old 12-03-2016, 11:45 AM
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Greg....I figured it like this....
All custom cams I've ever seen are ground straight up, split overlap, with no advance ground in unless you specify that they do so. So you've got 107 LCA and 107 ICL

So that makes the [email protected]" events:
Intake opens 14.5 BTDC
Intake closes 48.5 ABDC
Exhaust opens 48.5 BBDC
Exhaust closes 14.5 ATDC

Since the specs you've given were a near identical match to one listed in the cam chart of Vizards's Lunati cam grinds in Vizard's latest version of "How to build Max-Performance Chevy small Blocks on a Budget" (243 [email protected]", .635" lift, 106 LCA, the "max street" solid roller recommendation)
I used the 287 Advertised duration that went with that cam to figure the Dynamic on the Wallace Racing calculator.

At 287 advertised that put intake closure at 70.5 ABDC, I assumed 6.0" rod and 500 FT elevation and it gave a Dynamic of 8.43:1....advancing cam 4 for 66.5 closure gave Dynamic 8.71:1.

Any help ,at all??
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Old 12-03-2016, 02:42 PM
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EricNova: Yes, that was a ton of help and gives me something to go on. It took me only a short time to understand the 128 Vizard method, but he never truly addressed the few degrees of advance/retard and the effects. Thanx!

hcompton: What we are wanting to do is make an extremely healthy, and by that I mean about 600hp out of this little bullet and place it between the frame rails of a 2500 pound vehicle. Revving to 6500 will be fine, and since I've read that Vizard has been winning engine build-offs nearly every time he enters I was thinking he is on to something with his methods. These AFR race heads have extreme flow numbers and I was thinking we'd take advantage of that with about .635" to .650" lift. Vizard uses intended use to calculate overlap, and overlap and LSA to calculate duration. He says if you get the LSA and overlap figures you need for the intended use, the duration falls into place by itself. He's using CID to valve circumference ratio to calculate LSA.
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Old 12-04-2016, 04:17 AM
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Quote:
Originally Posted by Greg T View Post
64Nailhead: Something isn't right with that calculator. When I enter all the numbers , as a test, from my current cam card, it tells me my intake closes at 75. My cam card says 50
Send me your 388 cam card, head and piston cc, and rod length.
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Old 12-04-2016, 07:30 AM
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Quote:
Originally Posted by 64nailhead View Post
Send me your 388 cam card, head and piston cc, and rod length.
This is my current set-up: Edelbrock e-tec 200 head, 6.4cc pistons and 5.7" rod. (just for calculator calibration. This is not what is going together.)
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Old 12-04-2016, 07:36 AM
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I think it just hit me. The calculator is asking for advertised intake close and my card is showing @.050


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Old 12-04-2016, 09:13 AM
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Have you spoken with AFR? Their philosophy has always been "good heads mean you can get by with less cam." Did they recommend 220 heads for this engine?

I'm more of a street engine guy, and haven't built anything with more than 10.5:1 compression since back in the day when you could buy high octane pump gas, even 100 octane, on just about any corner. So maybe I'm way out in left field. But I can't see how DCR calcs tell the entire story. And they really aren't dynamic at all, because they don't take into consideration cylinder fill at any RPM above cranking speed. A DCR of 8.0:1 may not cause pre-ignition below the RPM at which peak torque occurs, but above that RPM, VE (cylinder fill as a percentage of cylinder displacement) may increase to the point where static compression comes back into play, especially with a 243/243 cam with 107 LSA. However, VE is not easy to calculate, but is a function of intake and exhaust velocity and valve overlap, along with intake valve closing angle.

Another thing: The DCR calcs rely on advertised duration. But is that at .004". .006". or at closer to .001" lift which is what GM uses? And with a solid lifter cam, how is that duration specified. Is it, for example, 287/287 before the lifter lash is taken up? After it's taken up, or after the lifter moves a few thousandths?

I'm just saying, I don't think DCR does much more than give you a rough idea of cranking pressure and effective compression at low-mid RPMs. There's a great article on this somewhere on a Mopar website, but I haven't seen it years.
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