Interesting Camshaft Video, Thoughts?

[Supercharged111]

The assertion is that every engine has an ideal LSA that can be calculated with simple math to within a couple of degrees. It's premise is that LSA comes first, and duration comes next based on desired usage.

There's a bit of talking and a bit of filler, but he does come full circle and the dynos support his claims. But I think I'd like to see 1 engine tested with multiple LSAs and durations to really nail the point home (or not). But I also feel that whatever duration he chose for the bill for a standard performance application. What do you guys think? I'm assuming ICL matched LSA for all of these.

 

[bracketchev1221]

Maybe I’m missing it with this argument. I’ve dealt with several cam grinders and have heard both sides of the story and I keep thinking they are saying the same thing. One side is saying lsa is the start, the other says valve timing is the start and let lsa fall out of that. But on the lsa argument side, it turns out that the formulas only seem to work for specific applications at which point there’s variables based on like 5 factors. I’ve looked at this for years and honestly can’t make rhyme or reason out of why lsa’s work. I’ve seen where all big motor cams were 112-114 or more in lsa but when I did mine for the 548 and 565 they were 109 and 110. There are so many variables to cam design and even if the lift and duration are the same, there are many factors in between that make 2 cams different.

 

[joesregalproject]

I'll admit the video was a bit lengthy so I skipped through parts, but if the argument is that mathematics calculates optimal LSA (and I don't disagree, engineers aren't guessing), I'd like to know how he derived that initial formula, the 128-(CI/8/VDia*.91)=LSA. Obviously you can see some things, but I'm not sure how it was derived. (CI/8)= cubes per cylinder, divided by (.91*valve diameter), is cubes per cylinder per 91% of valve diameter. Where did that come from? What is .91? 128 is the baseline for the LSA, but where did that number come from? And why is different for different engines? And why is compression ratio taken into account after all of this is calculated?

If you're using math, that's great, but you've gotta be able to explain where it came from.

 

[Supercharged111]

Maybe I’m missing it with this argument. I’ve dealt with several cam grinders and have heard both sides of the story and I keep thinking they are saying the same thing. One side is saying lsa is the start, the other says valve timing is the start and let lsa fall out of that. But on the lsa argument side, it turns out that the formulas only seem to work for specific applications at which point there’s variables based on like 5 factors. I’ve looked at this for years and honestly can’t make rhyme or reason out of why lsa’s work. I’ve seen where all big motor cams were 112-114 or more in lsa but when I did mine for the 548 and 565 they were 109 and 110. There are so many variables to cam design and even if the lift and duration are the same, there are many factors in between that make 2 cams different.

Indeed there are many factors, it got me to thinking that maybe this formula works best on cams within a given range assuming a top end that has a certain flow potential. Then again, to an extent, a cam's powerband can only be influenced so much by a set of extra crappy heads.

I'll admit the video was a bit lengthy so I skipped through parts, but if the argument is that mathematics calculates optimal LSA (and I don't disagree, engineers aren't guessing), I'd like to know how he derived that initial formula, the 128-(CI/8/VDia*.91)=LSA. Obviously you can see some things, but I'm not sure how it was derived. (CI/8)= cubes per cylinder, divided by (.91*valve diameter), is cubes per cylinder per 91% of valve diameter. Where did that come from? What is .91? 128 is the baseline for the LSA, but where did that number come from? And why is different for different engines? And why is compression ratio taken into account after all of this is calculated?

If you're using math, that's great, but you've gotta be able to explain where it came from.

I suspect that formula came from David Vizard and thus would require a few hours of Youtube sleuthing to answer. It seems one big assumption that is made is that port flow mostly varies according to intake valve size. But an LS head with a 2.00" valve flows a helluva lot more than a turd TBI head with a 1.94" intake valve, so there's that.

 

[bracketchev1221]

I tried the formula on my engines and it worked out to a 101 lsa. That was when it turned out to be low compression specific and there are more variables to calculate it so I’m not sure how it works. The cam I wound up and made just under 1000 hp was 110 lsa from the cam grinder. If you watch his video where David Vizard explains his formula, eventually he says it gives you a start. Not sure what that gets me, I can only afford 1 cam. I am not buying 4 cams to find the right one. And then he discussed pro stock motors how a change in LSA may not get you a drastic change maybe 5-10 hp. But in Pro Stock racing 5-10 hp is a HUGE gain, so not sure about that comment either. I don't admit to knowing a lot about cam design and I am not disputing his claim, just don't really understand what he's getting at. My previous 2 cams were done by an "let the lsa fall where the timing events put it" guy and they seemed ok. My last cam that I just bought is in fact by the guy he recommends based on having the most similar thinking to himself on LSA. So we'll see where that comes out because the formula says I should be at 103.5 LSA and the cam showed up with a 110LSA.

 

[Supercharged111]

After doing it for a few different engines, it seems that airflow per CI changes the desired LSA. So if you change a set of crappy heads and intake for something much better and leave everything else the same, the engine is going to want a wider LSA.

 

[78Delta88]

I spent time watching most of the David Vizard videos. Granted, it's a lot to unpack and digest.

One of the things I see with the LSA is the improved scavenging of the exhaust gas. Because of the LSA 104 to 108 you get a little of the incoming air fuel charge leaving with the exhaust gases, but you have better cylinder filling with the intake charge being more pure as it contains less exhaust gasses and like wise develops more power.

This is one of the things I would like to try with a test engine and a couple of days on the dyno, but don't see that happening very soon if at all.

Back in the EMT days I had a 78 Granada with a stock 302 that couldn't pull itself up a hill, let alone have decent manners even on straight and level. Off duty response Code-3 was basically nil with such bad road ability.

I put a Lunati 514/514 oval-track cam in it with Rhodes anti-pump lifters. Even with a stock 2 barrel and stock intake and exhaust it was a different car. I had a local shop put 2 1/4 duals with Hush Thrush Turbo mufflers. Total night and day difference, plus fuel economy improved.

It's just amazing when you get to a proper cam and air flow going, what it does to even the most basic car. I realized later that when the lifters pumped up it acts like high lift long duration, yet at around town it acts more like just basic stock.

Granted it was 2 barrel, stock heads, stock exhaust manifolds, but this is when I started to see the effect of longer duration with modest lift. What the LSA was, I am not sure, probably 108 or so?? Just know it worked.

 

[78Delta88]

This is a good one from Richard Holdener

 

[78Delta88]

Another one, a little lengthy, but good information.

 

[bracketchev1221]

This is a good one from Richard Holdener

But again, is it the LSA that is changing it or the fact that the valve opening and closing points have been changed that causes the change. Do you see my point? To me its a chicken or the egg thing, and it almost sounds like they are just using different terms to describe the same effect. If the engine calls for a later valve opening point and early closing point to make more power, the overall effect is a change in LSA. And the second guy he works with David Vizard on making video's, so he is just repeating what Vizard says. He's not any expert engine builder.