camshaft lobe sep

Currently laid off because of the GM strike and its a rainy day here in Michigan today, so i'm getting some reading in. David Vizard has some interesting writings no one seems to follow. Picking lobe sep is just one. He does explain correct compression as being a good thing to have to enhance air flow and states the higher you go with compression the wider the lob sep needs to be and my pipemax 4.5 suggests the same for my combo as 113-114 being whats needed with 262/270@50 duration. This lob sep is something I never see in N/A engines, power adder engines usually. Can anyone add anything to this mind set? I have always had the mind set 108/110 was what you used in an N/A engine.

First, I responded to your PM already.

Second... unless you're going to run about 15:1 CR and spin it 8000 RPM, no way in He11 I can see you needing a cam w/ that wide of an LSA N/A (unless it also recommends reducing the duration quite a bit, which wouldn't make sense to me, either).

DV has written a lot of stuff, and I own a lot of his books. However, some of his approaches, such as how he determines cam LSA based upon overlap, etc., seem tailored to fit all his SBC testing, despite his claims that they're universally applicable (for the most part).

I agree. His stuff seems way out there in my world. His lobe sep graph that figures lobe sep based on bore and valve size shows 100* lobe sep. for my combo. Never heard or seen anyone doing this. And now His lobe sep based on compression ratio goes totally out of the park the other way. Not looking to change cams right away, but I have been looking at the Ultradyne SLT cam grinds. They look to have a fairy quick ramp. Can these be run on the street without issue? Looking for a grind for 12.5:1 511 with 5000+stall and at 3380# race weight. The current ultradyne I'm looking at is very similar to what Dwayne spec'd and i'm using. the ultradyne has faster ramps and on a 108LDA vs my 110.

You can computer model and theorize all that cam stuff endlessly.

In the end, there’s only one way to know if it’s what your motor of combo wants....... and that’s to test it.

If the computer says it’s better, but your car is slower.........which are you going to believe?

Faster ramps will require higher spring loads(to achieve equal rpm), which will reduce the reliability/longevity of the components used....... no way around it.

The cam you have tries to balance that somewhat.

Would a more aggressive cam make more power? Probably.

The question becomes, how much more power does it make........and can I live with the ramifications of the more aggressive cam with the way the car is being used?

114lsa?
That doesn’t turn out very well in most cases with a build like yours.

Years ago i ran a 107 LSA comp cam Dwayne specced on a 416 motor that was just under 12 to 1
Scott Brown knew my motor specs well and suggested i try a 112 cam he designed
Car went 10.38 with the 107 cam, best ever with the 112 was 10.55
The 112 killed the 60 foot. Acted like novacaine when the car launched.
My take was more vert and compression it might have liked the 112 more.
Real good heads and lots of compression imo are necessities for an NA street/ strip motor to make that swap worthwhile at the track, maybe huge cubic inches might help a good bit top. Probably would

I'm the freakin' poster child for that... I don't even bother w/ the software stuff anymore. Empirical data all day long, please.

I agree, In the end its just entertainment for sure. 114 would not be a good direction after what I saw in a scott brown cam with 112lda in my 408. That thing was a pooch off the line and scott aways stood by that 112lda, said it might be soft off the line, but quicker thru the traps overall. I never seen it. Went to a 108lda and a 5200 8" from a 3500 10" and car went from mid 11's to high 10's.

I too have read a lot of DV stuff, most of it is spot on. One time I freshened an engine for a guy and all the exhaust valves were really pitted, I just thought it was cheap valves. It had a 108 camshaft installed at 102, on the dyno exhaust temps were very high, I took that to be the issue with the exhaust valve problem, got a new cam same lift and duration at 110 installed at 108 and the engine made 65 HP more and the exhaust temps came down to a normal range. Sometimes as mentioned an engine just needs what it wants, a lot of variables that maybe don't get inputed into a computer program the right way, who knows. I picked the replacement cam using performance trends soft ware, and pipemax software.

I had a similar experience. Scott Brown spec'd a cam for a 10.8:1 compression Edelbrock headed 440 combo I had w/ a 112 LSA (254/266 at fifty). I wasn't happy w/ it at all. Switched to an Ultradyne on a 108 (259 at fifty straight pattern) and the car went quicker and faster.

A lot of factors to consider when the LSA is being chosen for a particular cam. As for not seeing that kind of LSA on an NA engine depends on the NA engine. My junk is 117 NA, our dragster runs a 114 and the heads up car, which is also NA is even wider....Just depend on the application

No kidding Al? 117 lda or even 114 on an N/A deal? What in the combo requires being that far outside the norm N/A engine? Just trying to learn something here. Thanks, that's interesting.

I was told years ago(40+) by several people who worked for three different camshaft makers in SO CA that the LSA would help determine where the motor would make the most power, closer LSA would loose some power in the upper RPM limits(above 4000 RPM back then) and wider would loose power down low, below 4000 RPM.
I have used several different grinds in BB Mopars with 104 and one 101 LSA solid lifter cams
The one motor with the 101 LSA was a pump gas street stock stroke iron headed 440 that was installed at 99 on the ILC, the owner said that motor pulled real hard up to and over 7500 RPM
The 104 Isky grinds where used in several different higher (above 11.5 to 1)compression M.W. bracket motors, I would shift those motors them between 6400 and 7200 RPM

Winner, winner, chicken dinner!

Yeah Pro Stock stuff has been in the 120 range and some Super Stock stuff I've seen down in the high 90's. So LSA and LCA are just what it takes to get the job done. How you figure out what it takes to do the job is the tricky part.

Yep. Like i said above a bigger motor with good heads and lots of compression is going to shine with a wider LSA camshaft.
Hemi super stock because of rules is a much more limited motor and a more rpm band sensitive narrow LSA cam will shine.
For the typical bracket 10 and 11 second car that isn't light like a pro stock or heads up car, a narrower cam is typically gonna make the car ET better
Not gonna find to many 15 to 1 440’s or 416’s with eddie heads bracket racing because among other reasons fuel is expensive. Most “ class “ cars run narrower stuff. Talking stock and superstock

Chip, yea, Scott Brown was all about wider cams, no matter the situation. I was stupid letting him talk me into trying his cam. It didnt make any sense, and the results ended up predictable

I used to chase this stuff around but these days I use 112 in all of my street stuff with 4 degrees of advance. I don't even think about it anymore. Maybe I'm leaving peak power on the table but I don't care. 112 in at 108 works great on pump gas street engines, especially with EFI.

112 lsa is 112 lsa , no matter how much you advance the cam

On the street where the big inch big blocks you primarily fool with will blow the tires off at the hit, you likely wouldnt notice any difference. You are not wringing cars out at the track, are you?
Its not like the difference is huge in most cases anyhow. I learned over the years( at least to me) it takes 3 tenths or so to notice in the seat of the pants driving around after changes on the street and then going to the track.

Car runs 10.20 on the track and you drive it on the street. Make changes and drive it on the street and it feels the same. Take it to the track and the changes result in it going 10 flat. You think wow......wouldn't have guessed that pulling up to the ET shack

That’s true....... but it’s installed at some ICL.

True,

I seen the You tube video by D.V. awhile back and he has an interesting approach. I din't recall the specifics, but I think one of his comments was adjusting LSA to work with the car combination, not specifically to the engine.
I think he mentioned wider LSA so the car is not so violent out of the hole, then making more upper RPM power?

I reread DV's lsa article and applying his theory to my 511 with 2.200 intake valve, 4.375 bore and 12.5:1 compression it looks to me 108-110 lobe separation should work pretty good with this combo. In fact I believe dwaynes cam should work quite well in this combo(270/276@50-110). If i ever replace it I would go 108 before I would go 112 and with faster lobes and a tad more lift.

the 272/278 @ 0.050" in 110 LSA (HXL Lobes) pulls really smooth, but thinking I should have used a different exhaust lobe profile, or maybe just run 1.5:1 ratio rocker arms on the exhaust side vs the 1.6:1 ratio I'm running now.

That's what I did(1.6/1.5) and i'm thinking maybe I should have ran 1.6 on both as my exhaust flows 70% of my intake flow. From what I read/hear they should be 75/80%.

My take on it...a mild street motor that you're more concerned w/ street manners than speed...use a wide LSA.
Big cubes, big heads, and/or high rpm narrow powerband...use a wide LSA. Smaller engines that turn a lot of RPM use wide LSA too.
This is NA of course. Power adders change things. I'm no expert, but I've tried a few things over the years. Best thing I've done was talk to Dwayne Porter and learn from him.

A moderately headed 511" engine like the OP has is not one I'd consider a wide LSA for. Put some B1/MC heads on it, a tunnel ram, and a BIG cam to spin some RPM and it'd likely want something wider.
My 572 w/ heads flowing 430 cfm hemi heads only has a 112 LSA in it. My 446" w/ 340 cfm Indys uses a 108 LSA.

After trying that wide LSA cam in my 440 years ago and being disappointed w/ it, I talked to several other cam manufacturers for a recommendation. EVERY SINGLE ONE OF THEM recommended a 108 LSA cam for that combo.

I’d love to see a dyno test, for any make of motor, that saw any kind of real power gain, where the only change was the exhaust rocker ratio....... in a combo where the exhaust port wasn’t just horrible(relative to the intake port), or way too good for the application......... and the cam wasn’t just flat out wrong for the combo.

In other words....... nothing appears out of place or way off for the combo...... you do nothing but swap the ex rocker ratio...... and see a worthwhile improvement.

So, this may seem like apples and oranges here, but my experience with dynoing dohc engines, where changing lsa is easily done on back to back pulls, shows that THE most important cam timing event is intake centerline. It doesn’t matter whether it is NA or boosted/ nitrous. LSA on these engines seem to have minor effects when in normal ranges when NA. Much more pronounced on nitrous, a bit less so on boosted(turbo) never tried a supercharged example.

I agree, not worth the investment for little if any gain. If I ever change the cam, that would be the time for an exhaust lobe change if I thought it would be an improvement.

What are the trends you have seen moving the intake centerline?

I have a 348" small block built for NHRA SS/BS. It has 15:1 compression and is restricted to a 750 CFM carb. I have been messing with this engine for a long time.

A well respected cam guy at Comp recommended a more modern cam for it, it was ground at 115 LSA and was to be installed at 113.

On the dyno the engine made a little more power than the old cam, both were over 700 peak HP. However the guys at the shop that dynoed it thought the lobe center was wide for that engine.

The guy I had been working with at Comp left and I was assigned another. The new guy kinda wondered about it also and reground my old cam at no charge. The regrind had a LSA of 110 and was installed at 109.

On the dyno with the reground cam the engine made about the same peak HP but made more power and torque at all RPM levels below peak.

Your mileage my vary...

I played Rocker Ratio Roulette a number of years ago and found the only gains came from increasing the intake ratio. Adding the higher ratio did nothing to improve the on-track performance, which surprised me at the time because it was a single-pattern cam that looked (on paper) like it could use more valve lift on both sides.

This is exactly what I've found over the years. It's funny how the words always mouthed are "I don't care about peak HP I want bottom end" and "peak HP means nothing...its area under the curve that matters".

And yet, if the customer thinks the LSA is too "narrow" he will squeal his brains out and the cam gets changed out for a wider LSA, which means the timing had to change to do that. Doesn't matter that the area under the curve took a beating. Doesn't matter that the car would be quicker in the gear change because the CORRECT LSA made the middle of the HP curve fatter.

Doesn't matter. The customer is only right all the time when it comes to underwear and bras. J. C. Penney made a statement and the morons have run with it.

I was taught a long time ago to focus on the first 100 Ft. of the drag strip by Joe Alread (RIP) who was a many time NHRA SS national record holder and sponsored by Mopar back in the days before he quit drag racing due to NHRA politics

Comparing different LSAs between split duration and single duration cams doesn't
Work well. The extra duration on the exhaust side increases overlap, effectively making it a narrower LSA cam for three out of four events.

How did the HP look after peak? Curve after matters as well. I think as a general rule, if you compare hp only up to peak hp, the narrower lsa, and move advanced ICL will be the winner. But I don't think best ets come from shifting at peak, at least for me.

I thought Hod Rod did something like that. I don't recall the results. Off to the Googles!

I would think there would be more detriment to performance if the exhaust valve wasn't opened long enough vs being open too long a period of time. 1.5 vs 1.6. Just a thought

One of David Vizard's articles on rocker ratios had a test where increasing the exhaust ratio when the cam events had been "optimized" already resulted in a loss of power everywhere below the HP peak, and only a minor improvement above it. IIRC, his comment was that was a typical outcome if you're using a cam that has extended exhaust duration vs the intake.

Just the opposite of what I thought. ok, the combustion gas pressures are so high when that ex valve opens it doesn't require much of an opening to get out and the piston is helping it. The higher the compression ratio the better for evacuating the gases and getting fresh charge back in with a more complete fill. That's why i'm pushing my compression to 12.5-13.0:1. I may have to switch over to E85. With the E MW Victor head how many thou off per cc? Edel tells me .005, but not so sure with what I read over on another site.

Here's the gist of Vizard's article, since I don't see it online and am not sure I still have the magazine after The Great Car Magazine Purge of 2014 (or somewhere around then):
1. Intake more sensitive to lift, given sufficient duration, and generally "more lift is better"
2. Exhaust more sensitive to duration, and it's possible to have too much lift and/or rate of lift that causes losses in power
3. If you start with an "optimized" set of valve timing events and lifts, then start increasing rocker ratios (or go to significantly more aggressive lobes, I suppose), then your effective overlap triangle increases and it can require spreading the LSA to compensate
4. Too little overlap is worse than too much from a power perspective (doesn't take into account issues w/ excessive overlap w/ closed exhaust systems, though)
5. If you have to spread the LSA to get the desired driveability, what you probably need is a shorter duration cam on a tighter LSA to achieve the same overlap triangle and restore the lost torque from delaying the intake closing event

Please note that I'm not saying this is "The Truth", only that it's what DV discussed in that particular article. He also tends to be so focused on SBC and BBC that IMO he states things that don't necessarily apply verbatim to other brands/architectures of engines.

I have his book and yes that's pretty much what I remember reading. Your number 4about excessive overlap came into play when Dwayne spec'd my cam. He asked if the combo would have exhaust and said it would need 110lsa with exhaust and a 108 would work better without exhaust. So, I agree to the best of my understanding.

I was under the impression that bigger motors like a wider lobe seperation . So a 600" motor may respond better to a 114-116, a 500" may run better with a 110-112, a 400" motor may like a 106-108' , etc....

Exhaust far more sensitive to opening point than to lift. Once the valve cracks open, there is easily 70 psi escaping. Compare this to perhaps 1 psi at the intake seat...

Comparing LSA between cams is meaningless unless that's the only change.

Here it is No surprises here SBC with a small HR cam.

Like about 90% of the questions asked here, the only valid answer without knowing more of the details is: "It depends..."

Yeah, almost like shooting at a moving target. Every combo is different. It would be nice if all the convertor guys, cam guys, cylinder head guys and what ever guys got together and wrote a book on a bunch of different combos to show what works and what don't.

I have played rocker ratio roulette before myself. On my current predator deal in fact. I have even played with lash as well. Usually if you find something with ratio or lash for a given cam all you are learning is that you likely didn't get the correct cam the first time.

FWIW my current predator had a few cams and different ratios in it. The current one picked up 25 peak HP and 22 average from opening up the intake lash .010 and closing the exhaust .015, so what's that tell you? It made the best average and peak and is still in the engine but when we freshen it will likely have a new cam in it once again. And let me tell you those 60MM stocks dont come cheaply but I am trying to dqueeze all I can from this limited bore engine, while still maintain some semblance of reliability, so far so good on both fronts.

Actually, that’s a camshaft LSA test in the link, not an exhaust rocker ratio test.

I would have to dig out the dyno sheets but my recollection is that the power was flat after peak. However we did not run it very far past peek. On the track both cams quit pulling at peak.

Sounds like you dyno and track tested both cams.
115lsa in at 113 vs 110lsa in at 109.

Which went quicker, and just how much difference in ET between the two?

I tested several (3) different camshafts years ago on a NHRA legal 1971 340 stocker rmotor , two Isky cams with the same lobes with one on a 107 LSA and the other on a 105 LSA. I moved both of these cams from 2 degrees retarded in two degree increments to 6 degrees advanced in the same motor on the same day The 105 cam advanced 4 degrees on the ILC made the most peak HP and torque. Both of those cams made peak HP right at 5900 RPM and had a very steep gain and drop off after peak HP reaching 430 HP. those cams would make under 390 HP at 5000 RPM and droop off to less than 400 HP at 6400 RPM Both of these cams had rounded tops on both lobes like most roller cams have, not a V shape nose
The last cam was a Lunati brand with V nose lobes ground on a 106 LSA , I move the ILC around just like I did on both of the Isky cams, this camshaft made 10 HP less at peak RPM(5800 RPM making 420 HP from 5600 to 6200 RPM and it made 400 HP at 5000 RPM all the way to 7000 RPM with no drop off
My message is the total package on the cam designs need to be look at very closely to help you decide on what to use for your deal

Unfortunately I don't have a definitive answer on track times. The new cam seemed to have more horsepower, enough to introduce some chassis problems. All the car wanted to do was turn right at the start. I found some things wrong with the chassis but that did not solve the problem. Turns out it was a bad slick. I got new tires and it went straight.

However tighter LSA means less valve to piston clearance. I knew that and checked it. It was tight but not as tight as some folks said they got away with on this thing called the Internet.

Turns out the exhaust valves were touching the entire time I ran this cam. At 6,450 RPM in low gear a head came off an exhaust valve and destroyed the block. I am in therapy, the head is being repaired and a replacement R3 block I had is in Maryland being machined.

Maybe I can give you a better answer next spring.

The “new cam” being the 110lsa?

Not sure how much on average narrowing the lda would also narrow piston the valve clearance on a 4.25 stroke, But I currently have 110*lda and .160" clearance on intake valve and .230" on exhaust. I would be sure to measure if I went 108lda, but looks like I have a ton of room as is.

Yes sir...