David Vizard. High Lift Low Duration ?

[427HISS]

I came across a article and video's from an engine builder David Vizard talking about cams, springs, lifters, oil, additives, etc. From my small search I've found that some think he's a god on engine building. I watched one video so far, and although he sounds pretty conceded and likes to sell himself, he does sound like he knows what he's talking sbout.

And I'll say, I do not know him, work for him, run his seminars or think he's a God, so please don't jump on my back.

[wsu0702]

I bought this book when I was in college back in 1990 and read it cover to cover.  I didn't know shit back then and took it as gospel.  But 30 years later and a little more informed now I can say that I think that he was spot-on on almost everything stated in that book. JMHO

[Joe-JDC]

When I bought my Super Flo 600 flow bench back in 1994, I asked the sales representative about what books and information was available for me to learn everything I could about flow and porting.  He said there was only one book he knew about that was good information, and good theory.  It was a book that is out of print, by David Vizard.  I bought it, studied it, and used it for all my work for the first 5 years with my personal flow bench.  I had worked with two shops before that with flow benches, and they didn't have any technical books to learn from, they just worked from stock to ported change in flow.  I studied David's drawings, his theory, and I started improving dramatically in the ability to get the most from just about every head that I worked on.  Yes, David is a bit self important, but he was the only one in print for several years.  Now there are so many simulation programs available, they try to debunk him, but his theory is solid, and he does get results.  Has the industry passed him by?  Not yet, but everyone else has caught up, and with CNC available, we are still learning what works even better.  I have talked with David personally, he has called me here at home, and I respect what he has accomplished, whether I agree with everything or not.  Joe-JDC

[Katz427]

I worked in a lab with a couple of aerdynamicists back then. This is before CFD. They always described it as a "black art". They knew, respected, Vizard's knowledge of air flow, for indeed it was, and still is IMO a "black art". Why I still listen carefully when JDC speaks. That knowledge comes from years of work and close observation, you just can't replace those, many years of experience, and the knowledge gained, easily, even with CFD.

[WConley]

I've got to agree on the experience thing.  At Ford we had a big problem with the first pre-production 4.6 Modular V8's.  The pistons were pretty short for a production engine of that era.  They were slapping in the bores, and there was nothing our army of engineers with the latest simulation tools could do about it.

Finally they brought in Don Sullivan, who was well into his 80's.  Don fixed the issue with the right recipe of pin offset and skirt shape.  It helped that he had seen everything at Ford, starting with the original Flathead.  There will always be a need for the graybeard.  I'm counting on it!

[Barry_R]

I've known David V for quite a while.  He is an interesting character, who has had some "life challenges" these past few years.  But the value residing in the amount of information he has acquired and relayed to folks through hundreds of articles and books can not be understated.  We can certainly find individuals who have gone beyond him in their fields of expertise (he really should not try to argue with Randy M about carbs at the EMC deal...Randy designed many of the popular carbs while working at Holley...).  But overall one cannot help but admire the talent that he has shared, and he has brought a lot of us along for the ride as we were growing up in this industry.

[427HISS]

I'd like to discuss his high lift low duration.

Other than measuring the CFM of you heads to find out what your max lift should be, what else is needed ?
Duration ?
Size of the valves ?

If your port's are as big as they can be, does determine size even matter if you know the flow numbers ?
Shouldn't every engines intake and exhaust ports be as large as possible and match exactly to aid in the cams lift and duration ?
Does the type of fuel and octane change anything in the lift and duration ?

[chilly460]

Read some of Vizards books, and followed some of his posts on Speedtalk.  I think he can definitely help out anyone just starting to gather info. Seems like guys try to discount what he says at times due to his personality, more so than his actual data.  I do recall he and Mike Jones were going to design cams and see whose ran better in a combo, and turned out that once they unveiled their designs they were so close they concluded they didn’t need a comparison...Jones is a well regarded cam guy so seems at least for that example Vizard at least has a clue on cam design. 

Port size, IMO, should be small as possible to hit the hp/flow requirements that are desired.  There are valve size, curtain area, cross sectional area, etc to consider.  No need to run a huge CSA if the bore will only support a 2.00” intake valve. 

The cam should follow the characteristics of the heads, not the other way around. 

Fuel and octane restriction can impact cam design, say if a combo is running pump gas and due to existing piston/combustion chamber size is going to borderline on detonation you can run a cam with a bit later intake closing to reduce dynamic compression...and probably a few other ways

[427mach1]

I worked in a lab with a couple of aerdynamicists back then. This is before CFD. They always described it as a "black art". They knew, respected, Vizard's knowledge of air flow, for indeed it was, and still is IMO a "black art". Why I still listen carefully when JDC speaks. That knowledge comes from years of work and close observation, you just can't replace those, many years of experience, and the knowledge gained, easily, even with CFD.

I worked 34 years as an aerospace engineer at the Lockheed Martin Low Speed Wind Tunnel (see my profile photo).  When I was in grad school back in the mid-80's, we were told that in 10 years, CFD would replace the wind tunnel.  By the mid-90's, CFD had advanced to the point that, in 10 years, the wind tunnels would be obsolete.  In the mid 2000's, I worked on an F-16 project testing CFD-designed parts.  Most of them didn't work and they were over-nighting us new parts to try almost daily, telling us that these were the latest updated parts that should work.  We did eventually get parts that worked but CFD was still in developmental stages and needed 10 more years or so.  By the time I retired last year, CFD had improved so much that in 10 years, wind tunnel testing will probably no longer be required.  I can't tell you how many tests we ran to "validate and fine tune the CFD code," i.e., change the code so it matches the wind tunnel results.  CFD has been somewhat helpful in gross configuration development but it will never replace the wind tunnel, just as the wind tunnel will never eliminate the need for flight test.  There definitely is something to be said for the "black art" of airflow.

BTW, we had our own definition for CFD,  Can't F'ing Decide.....  Sorry for the rant, I'll get off my soap box now!

[allrightmike]

In regard to high lift short duration, isn't there a limit to lift rate or amount of lift per degree of crank rotation? Seems if taken to it's limit high lift short duration would limit RPM quite a lot.

[Gaugster]

I am binge watching Mr. Vizard's Power Tec 10 videos now. Cool stuff. He seems to have a very practical and highly observant, curious approach. I had a chat with an online cam tech recently. When it came to high lift (approaching 0.7" gross) I got the impression that low RPM (1500-2200) may suffer as the question of torque converter stall came up. Guessing that the port velocity might not be enough for what folks consider a well behaved street car. Displacement being a huge factor. Just a reminder that I'm the dumb blond around here but learning as I go.

[blykins]

When speaking in camshaft terms, everything is relative, general, and vague.  It's only when you get into one single specific application that you can zero in on where the lift should be, where the duration should be, where the overlap should be, etc.

For instance, what's high lift to you?   High lift to me is 1.050", but I get some customers who stand with mouth agape when I suggest to them a .570" lift camshaft. 

It's very common for me to run .630"-.650" lift at the valve on a hydraulic roller street cam.  Lift in and of itself does not affect rpm or rpm manners, unless the lift is too high for the cylinder heads and the heads are turbulent at that particular lift.   

However, too much duration can certainly get you into trouble when it comes to an engine's behavior on the street. 

What I have found out over the years is that most guys associate the lift with how the cam will behave.  That's certainly not the case.  "I've got a .600" lift cam in this thing!"  really tells me nothing except that it has .600" lift.  It tells me nothing about where the rpm range will be, how it will sound, or if it will have enough vacuum to run the brakes.   True camshaft specs will involve .050" duration, .200" duration, advertised duration, lift, how much overlap it has, and where the valve events take place.

[427HISS]

In regard to high lift short duration, isn't there a limit to lift rate or amount of lift per degree of crank rotation? Seems if taken to it's limit high lift short duration would limit RPM quite a lot.

You're Very impressive !
I like the,...''CFD,  Can't F'ing Decide'' lol...

I've been working on my engine on and off for three years, and I still,....can't decide on a hydraulic roller or a solid roller and specs !
I think ok,.I'll go with this company, type and specs, then the next day I read or hear something different, then I'm back to damn,....start over. lol. 
I know that several guys here are rolling their eyes to the top of their brains thinking, how many times has Kevin talked about this ?   Just pick one, install and drive the bitch !

[Blueoval77]

People go on and on over how much the Hydraulic lifter has improved . I think making the statement in itself should answer anyones questions about them . Like with anything however it really is needs and expectations specific... Me of course needs them to not do what hydraulic lifters do and me of course expects them to piss me off...

[blykins]

People go on and on over how much the Hydraulic lifter has improved . I think making the statement in itself should answer anyones questions about them . Like with anything however it really is needs and expectations specific... Me of course needs them to not do what hydraulic lifters do and me of course expects them to piss me off...

It's like anything else:  you have to experiment and learn.   With the right valvetrain and camshaft, I have no issue going to 6500-7000 and even higher with a hydraulic roller.   Would I always choose a hydraulic roller over a solid?  No.  Do they work in the right application?  Absolutely.

I'll leave this here:

https://www.youtube.com/watch?v=C_JY47anClA