DRIVESHAFT

Most fuel injection systems use a MAP sensor, which senses vacuum.
The low vacuum levels caused by lots of overlap drive them nuts.

Little Mouse

You like comp cams you could use them as an example or the other cam companies they all say the same thing.

Bracket cars are generally just 3 speed atomatics most of the time they are heavy a lot of the time not even geared for any form of serious drag racing just your average guy shows up with his 3400/3800 street car or maybe even a 4000 pound+ pickup truck to have some fun hoping to win. Any time heavy bracket car or the word heavy is used, you see 106 to 108 LSA, they also have only three gears in the auto for any torque multiplication. When you see lighter weight vehicles listed you see the LSA widen to at least 112 or more, these cars with very high compression lighter weight may well have a five speed manual race trans. I would take a 108 LSA in a heavy street car with pump gas friendly compression.

Comp cams makes a nice compromise on its hydraulic cams uses a lot of 110 LSA the wider 110 helps retain some more idle vacuum but does not stray far away from the power 108 LSA.

63mako

Sounds like we are in agreement here. For some intended uses a 108 LSA cam is the right choice. For some intended uses a 112, 114 or even a 120 LSA would be the right choice. I have a car that weighs #3000, Highest compession I can safely run on pump gas, Nitrous, 6 speed manual, 4.11 gears. Street use. 114 LSA

cardo0

Power under the curve will win the race.

Not only will the a tighter LSA will make more peak torque but it will make significant more torque and power for the entire powerband. Even if the wider LSA cam makes more rpm and more peak hp the tighter LSA cam will get the same car to finish faster as it accelerates the same car faster for nearly the entire rpm band. Some are incapable of absorbing this and continue obscure the original post - a tighter LSA cam makes more torque. OP said nothing 'bout a streetble cam or "how to make a 600hp streetble sb". BTW how many streetble 600hp sb's are there. And how many even want to spend the $$$ to try to build a 600hp sb - get real.
Considering street manners is another topic entirely. Trying to influince others that a wider LSA is somehow neccessary in every combo is a distraction and cover-up for bad planning and research.

Yet some continue to post misleading info. I still read posts here like a tighter LSA will make more top end power and that is totaly wrong. The tighter LSA makes more power by more mid-range torque for a larger part of the power curve. The wider LSA will idle better/smoother, come up on the cam a little earlier, and make more rpm and of course more peak hp. But the tighter LSA makes more torque and power inbetween the ends of the power band. Some here are incapable of understanding this and continue to try influence others with a nonsense understanding. They won't stop posting, they just keep trying to distort the OP to make up for thier lack of understanding.

cardo0

63mako

I have no lack of understanding and never said a wide LSA is the best for every combination. You are the one posting misleading information and obviously have a lack of basic understanding. I have said all along in almost every one of my posts, both a wider LSA and a narrower LSA have their place. Well, I read your profile and, With a stock L48 with a top end kit a narrower LSA might make sense for you. It will boost your effective compression and with your mild cam, low compression and mild build vacuum and idle quality is not an issue for you. Making the most out of a stock bottom end and building an on the edge street/strip engine from scratch are totally different. I will repeat this for those who just don't grasp this.
On a 600 HP 11 to 1 small block build in a street car the biggest issue is the ability to have enough vacuum to run accessories, idle well enough to be able to use the car in in town and stop and go cruising, being able to run pump gas while avoiding detonation. On a race engine it is maximum power at WOT in the rpm range you use in the 1/4 mile and if it don't run on pump gas run race fuel. Different builds and goals. I will post some facts here to try to clear some of this up. This is right from Comp Cams techical information website:

EFFECTS OF CHANGING LOBE SEPERATION ANGLE (LSA)

Tighten (smaller LSA number)......... Widen (larger LSA number)

Moves Torque to Lower RPM..........Raise Torque to Higher RPM

Increases Maximum Torque............Reduces Maximum Torque

Narrow Power band......................Broadens Power Band

Builds Higher Cylinder Pressure........Reduce Maximum Cylinder Pressure

Increase Chance of Engine Knock....Decrease Chance of Engine Knock

Increase Cranking Compression.......Decrease Cranking Compression

Increase Effective Compression.......Decrease Effective Compression

Idle Vacuum is Reduced.................Idle Vacuum is Increased

Idle Quality Suffers.......................Idle Quality Improves

Open Valve-Overlap Increases.......Open Valve-Overlap Decreases

Closed Valve-Overlap Increases......Closed Valve-Overlap Decreases

Natural EGR Effect Increases.........Natural EGR Effect is Reduced

Decreases Piston-to-Valve.............Increases Piston-to- Valve Clearance............................... .....Clearance


The above areas highlighted in red would generally be an advantage in a 11 to 1 600 HP street motor trying to run on pump gas!

If you raise your static compression a little with a wider lsa you can regain most if not all of the negative power effects of running it and still use pump gas because you lowered your effective and running compression with the wider lsa. With power adders this is a big plus. You will have a smoother idle with improved idle quality, more vacuum, a broader power band, less overlap, better piston to valve clearance which will allow you to run more lift to further negate a slight power loss. Like I said before, The drop in power on the initial test was 3% from 107 to 113 LSA. Increase static compression and lift a little and advance or retard the cam a couple degrees to obtain maximum power this difference is gone and you have a much more streetable 600 HP small block. I will guarantee the 107 cam motor with the specs on the initial test won't run power brakes, wiper, headlights as effectively as the 113 lsa if at all.
Something else that hasn't been addressed is the fact that a narrow LSA car with less bottom end power will hook up better on launch at the strip then pull hard once it hits the power band. This is great at the dragstrip, not so great taking off from a stop sign.
The majority of people on this site are looking for streetable power and are willing to plan carefully and maybe give up a few peak HP for better street manners, especially on a 600 HP street engine and you would be suprised at the number of corvette owners that are building 550 to 600 HP small blocks that spend most of their time as a street car. I can't sit by and let people like you, with admittedly very little real experience give them false information without posting some facts that I have accumulated in the last 35 years building both street and strip cars that are confirmed by Comp Cams techical information posted above.
Every owner and build has different goals. Best bet is to figure 110 LSA as a base and use LSA as one of the variables you can adjust just like lift and duration, hydraulic or flat tappet, hydraulic or solid roller, head port size, static compression, DCR, intake selection, carb size or FI, header tube size and long or short tube headers, Stroke, bore size, deck height, gearing, power adders and a variety of other factors to build a correctly matched unit for your intended use and goals.

cardo0

Tight LSA or wide LSA is a relative term. Meaning what is wide for one combo maybe tight for another. Major factor is cubic inches compared to vlv size. Others are induction system. Independent runners like the old weber carb set-ups just breathed so much better without any dilution (from adjacent cylinders) that it provided optimum LSA at a much wider angle than with a typical single (or dual) plane intake.
What we are after here is Volumetric Efficeincy (VE). This is when the tighter cam is used to optimize VE rather than a wider LSA to detune the eng combination looking for better idle charateristics, lower Hydro Carbons and lower Carbon Monoxide for smog issues. Most libraries have plenty of good books on internal engine designs for performance (try the reference book section) that can fully explain VE. And i can see that some here are ready for more objective technical advice and would likey enjoy reading that also.
What some don't get is the higher VE makes more power for more of the rpm range. Even after 35 years, some just can't see how a 550hp (or maybe even a 500hp) motor can be faster than a 600hp motor. For a tighter LSA the answer to excessive overlap is a smaller (duration) cam. The smaller cam with tighter LSA can make just as much torque as a larger duration cam though it will quit breathing at a lower rpm. But it still has an higher VE and will make optimum torque for a larger rpm range the a bigger cam with a wider LSA. The advantage is the smaller cam requires lower vlv spring pressures and allows a longer cam life. How long does a cam over 280* full duration live? I've read <50,000 mi - but i can't prove this so take it for what its worth (billet roller cams may live forever even though the vlv train won't).
If we're talking street manners here - but not smog legal cams (another subject entirely) - the short cam with tighter LSA is the real winner. But again the OP said nothing 'bout street manners. Only talking torque with using a tighter LSA and the higher VE is where it wins.

If u still don't get it then enjoy your wide LSA motors with less than optimum torque all u want. Anything over 500hp on the street is really wild and unlikely anyone else will ever know what your LSA is.

cardo0

v2racing

63mako is right on the money here. There are problems with this test such as the IC and the DCP, but there is even more. I have done a lot of work with wave tuning and I can tell you that the exhaust timing events need to be matched to the exhaust system to make the testing fair. A change in primary or secondary (collector) dimensions along with the corrected compression would likely have shown very different results for each cam. They also don't tell people about the idle quality, the off idle response, or the vacuum produced. These are all very important factors in a street car, which most of the people reading these articles have. Also keep in mind how well you can control the engine temp on a dyno and that the engine is not stuffed in a heated engine compartment with a hood over it. I doubt very much if you could run 11.1 to 1 with 37 degrees of ignition timing on 91 octane in a car on the street with the 107 LSA in this engine.

The test misleads readers into believing that any cam they choose should have 107 LSA's. This could lead to disasters in some combinations. Look at the 406 in my signature. It is a 600 horse street motor that runs on pump gas with 11.8 to 1, it's walking a fine line, but it does. It also has decent enough vacuum to run all of my accessories including my power brakes. It has a 110 lobe center, if I was to narrow the lobe center to 107 and maintain a 4 degree advance, it would no longer run on pump gas and my vacuum accessories would no longer work well. It would also not get along very well with my 2800 rpm stall. It would need more. Of course it is not only the 110 LSA that makes this engine combo work, other things like a very tight squish (quench) making an efficient chamber even more efficient help too. This motor makes it's power at only 33 degrees timing. Because I matched my components for the results I wanted, it worked out very well. It is all about using the right combination of parts and specs to achieve the results you want! There is no magic number for any one of the specs on a cam.

Oh, and as far as for racing, Pro Stock cars run 114 or larger LSA's, so again, it's the combination and usage.

Now I am on my way to bed. I only peaked in here on my way to bed and saw this thread. I had no intention of staying up this late and writing a post.

TheSkunkWorks

As a matter of fact, those of us who see fault with the test DO very much get it.

One more time: Something conspicuous those of you who fail to understand and/or refuse to admit about the test is that the ICA was NOT left constant, which resulted in earlier intake valve closings, introducing an unaccounted rogue variable which skewed the VE%'s and ultimately the torque/power curves to falsely indicate more average torque than would have resulted had the ICA been held constant for the test, or had the CR's been adjust to equalize DCR's between each combo. Should either of these latter compensations been made, while the narrower LSA admittedly would have had a higher peak torque value than the wider LSA, the overall average torque most likely wouldn't have varied much at all, except if the bandwidth reported were manipulated to purposefully reflect a particular trend. Like it or not, this is fundamental to the whole issue here.

Ultimately this test was actually about earlier ICA's in combination with narrower LSA's, rather than it being strictly about narrower LSA's as was presented. Unfortunately, by not accounting for that rogue variable mentioned above, the article's author draws conclusions "we" contend are misleading to those who can't themselves read between those lines. #*@&#%!, even CompCams own tech page on LSA's is in agreement with what "we've" been trying to get across...

http://www.compcams.com/Technical/FAQ/LSAproperties.asp

Go ahead. Read that and then explain to me all about how raising peak torque RPM, broadening the power band, decreasing the chance of engine knock, increasing idle vacuum, improving idle quality, and reducing the natural EGR effect are mistakes for my purposes. Ah, but you can't exactly do that without knowing what are my purposes.

Thing is, the specific "benefits" of narrow LSA's aren't best suited to every application, but don't let that fact stand in the way of your installing a narrow LSA cam in everything you build from here on in based on your misunderstanding the "wisdom" of this article. I, for one, will be taking the time to consider what LSA matches up best to each given application, foreign as that concept may seem.

And, to think I promised myself I wouldn't return to this thread only to find myself up past my intended bed time over this again... Where is that ignore list button again, anyway?


edit - v2racing

63mako

My VE is 100% from 5000 to 6500 RPM with a 114 LSA. More lift and a faster ramp rate require stronger springs not more duration. Explain to us why a pro stock engine uses a 114 or higher LSA.

v2racing

EFFECTS OF CHANGING LOBE SEPERATION ANGLE (LSA)

Tighten (smaller LSA number)......... Widen (larger LSA number)

Moves Torque to Lower RPM..........Raise Torque to Higher RPM

You make more horsepower by by making torque at a higher rpm. Torque x RPM / 5252 = Horsepower

Example: 700 lb/ft x 4500 RPM / 5252 = 599.8 Horsepower

700 lb/ft x 9000 RPM / 5252 = 1199.5 Horsepower

Something to read from Darin Morgan (Pro Stock head builder fame) on another forum:

Guest wrote:
Just wondering if Darrin would give us a ballpark idea of the cam specs for a 500" Pro Stock motor. I'm aware that valve lift is better than 1", but just wondering how much duration is required to run at such high rpm. Does an IHRA Pro Stock motor have significantly more duration than a NHRA Pro Stock?

Darrin Morgan wrote:
A typical Pro Stock camshaft is a 570 lobe 284 duration on the intake 560 lobe 304 duration on a 117. The rockers are 1.85 intake and 1.8 exhaust. Its no real super secret. That is about the average cam profile we use. We have bigger cams but they tend to hurt parts over 9800rpm. We will be going bigger in the near future. With the bigger core cams comes more lift. We are now at 1.050 to 1.060 gross lift with as little deflection as possible so the net lift is probably about .990 to .995. ( I am guessing) That does not tell the whole story. With lobe loft we actually get a dynamic 1.100 lift above 8500rpm.

The IHRA cams are 600+ lobes but I don't know what people are using in the duration department. I would expect it to be in the 290s at .050. They have REALLY wide LCs at or above 120. They can be much more aggressive on there lobe profiles due to the fact that they don't exceed 8500rpm

63mako

Yep. Hey Skunkworks, Thought you were done. When I went to 114 LSA it did raise my peak torque RPM. Went from 6200 to 6500. Went with a rev kit and stud girdle to retain valvetrain stability with the HR @ higher RPM. Also wanted to have a lower lift and lighter spring pressures for durability. To get this and maintain HP. increase cylinder filling and VE you need duration. The rev kit helps run a HR @ higher RPM by putting extra spring pressure on the hydraulic lifter body not the internals to keep the lifter planted on the lobe, similar in effect to a stronger spring. With duration increase comes increased overlap which, on a street motor causes you lose streetability on many levels (try driving an L88 on the street on pump gas). To offset that one way is to widen LSA, which in turn allows you to increase compression and still run pump gas while minimizing power loss. No one size fits all on cam LSA selection. Intended use and matching component selections and build specifications to optimize your use is the correct way to go. Some guys read an article in a magazine and think they got it figured out.

TheSkunkWorks

63mako, human nature being what it is, sometimes you just can't pass a train wreck without taking a second look. It's so easy for guys who don't understand as much as they think they do (we've all, myself included, got to be able to accept that we don't know everything) to miss important subtleties and get wrapped up in chasing max numbers, that I thought I'd give it one more shot for the sake of the ones who are actually trying to learn something. And, I haven't quite reached the point of just throwing up my hands and following members like Lars outta here, just yet...

v2racing's post on wave tuning brings up another reason you can't look simply at LSA's, as I had tried with apparently little effect to point out earlier. When you get down to it, LSA's are really a secondary statistic of timing valve opening and closing events and that of max lift to achieve such all important tuning on both intake and exhaust. It's just easier for most to grasp the idea of LSA's than to work out the complexities behind that spec.

Little Mouse

I'm thinking a pro stock engine has somewhere around 120/122 LSA
( read it somwehere lol ) big time compression to work with, upper end power is all that matters for them.

rham

Since this is still going thought this might be an interesting read for all.

http://www.stockcarracing.com/techar...les/index.html

TheSkunkWorks

Well written as that article is, and as much as I respect Vizard, I'm not about to consider putting the ICA at 104* (that's where the chart would have my 427 + 0.030" w/2.19" intakes) in the BB I'm on right now. As well as having spent many hours doing high-end sims (which include extensive wave tuning projections, btw), my election to position my ICA a good number of degrees later is also based on my having been around the block a few times, listening to sound advice, and NOT being dazzled by numbers to the point of loosing sight of the overall picture. For my purposes, a 104* ICA would be the single biggest mistake I could make. But, thanks for sharing.



edit - FWIW, that 2D chart doesn't take into account at what point a particular combo reaches max piston velocities, or how much area is under a given cam profile. There are many more dimensions involved in this.

v2racing

The chart doesn't take compression ration, the rpm range desired, how good the low and mid lift flows are on the exhaust and the intake (he does mention intake low lift in the text) or even what the engine the cam will be installed in will be used for either.

I looked my engine up on the chart and it called for a 105 LSA. That LSA would completely eliminate the streetability in my engine. Lower vacuum, rougher idle, higher DCP so no more 92 octane. How is this the ideal LSA for me?????

v2racing

Check out the quotes of Darrin Morgan from another forum in my post 3 posts above yours.

rham

You guys obviously know more about this stuff than I do, I like to learn as much as I can so I do read a lot. I thought Vizard made mention that other factors like compression, better breathing heads, rocker ratios among other things have an affect on lca. I have read a couple of his books and he also makes mention that you may have to widen it to have good street manners. He has recommendations for overlap amounts for street driven cars all the way up.

Of course on the other hand I have talked to Harold Brookshire (Ultradyne, Comp, Lunati VooDoo), and he does not agree with some of what Vizard believes. For guys like me looking for the easiest, cheapest way to make 400 horsepower with a 350 it makes the cam decision a lot harder!

Little Mouse

Yep did not look at all the posts, just remember reading something on pro stock engines they use wide LSA, makes sense.

But to the above arguments the bottom line if tight LSA cams were
the answer to everything thats all the cam companies would make
same goes for wide LSA cams, it could come down to a lot of things
what your going to use the engine for, what parts are in it.

63mako

Right on the money. Intended use and component selection. The article by David Visard above is out of a stock car magazine. In a stock car off idle throttle response, vacuum, part throttle cruise and response, fuel mileage, rough idle and ability to run pump fuel at a given compression ratio don't enter the picture. It is all about maximum power obtainable within the specified rules. Again, compression ratios and intake closing points aren't adjusted to level the playing field. If you look at the chart the graphs start @ 2500 RPM. Look at the begining of the graph line and you will see the lines, if extended toward idle would show a much different picture below 2500 rpm. If you have a street car with OD where does it live? If you have a 500 to 600 hp small block street car will you sacrifice a small percentage of peak HP and torque to be able to pick up below 2500 rpm throttle response, enough vacuum to run the accessories that require it and assure that you can safely run pump fuel without detuning the engine or having to increase cam duration and overlap to further impede low end performance?
I will go back to the New ZL1. They want maximum streetable power and low end driveability. It has a supercharger, it runs 11 to 1 compression, it runs over 120 LSA. If Vizards article was carved in stone the big CI pro stock engines would be running cams with LSA's at 100 or below.