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What is the largest LSA you ever saw on a Solid roller
#548903
12/08/09 01:51 PM
12/08/09 01:51 PM
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Joined: Aug 2005
Posts: 759
Southington Ct.
turbobitt
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Southington Ct.
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Just as the title says, What is the largest Lobe seperation angle you ever saw on a solid roller cam and why.
Looking for a general idea of what people have tried. I have a turbo powered car and looking for ideas and a general sense of the "Norm".
Allan G.
Last edited by turbobitt; 12/13/09 12:56 AM.
1970 Challenger w/572 Hemi street car and my pride and joy.
1986 T-Type with 272 Stage 2 Buick V6 engine - True 8 second street car. Just updated the engine and put down 928 HP @ 35# boost to the ground on chasis dyno.
1976 Cee Bee Avenger Jet Boat - 460 Ford powered.
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Re: What is the largest LSA you ever saw on a Mech roller
[Re: turbobitt]
#548904
12/08/09 01:57 PM
12/08/09 01:57 PM
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Joined: Nov 2003
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Rock Springs
Bob_Coomer
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Rock Springs
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Howards has some pretty wide stuff.... Big Chevy 4/7 swap cam says... Very large Cubic inch with big multi stage NOS systems... LOL Cam part # 124093 it has a 118 LSA  It will never be as cool as my Silly cam though 
Last edited by Bob_Coomer; 12/08/09 01:58 PM.
[color:"red"]65 Hemi Belvedere coming soon [/color]
[color:"#00FF00"]557" Indy engine 1.07 60ft 144mph in the 8th 2100 lbs package [/color]
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Re: What is the largest LSA you ever saw on a Mech roll
[Re: aarcuda]
#548908
12/08/09 02:16 PM
12/08/09 02:16 PM
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Joined: Jan 2003
Posts: 965
Odessa, Fl
blowndart
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super stock
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Quote:
whats the advantage of wide LSA besides a nicer idle?
Less overlap. Overlap on a turbo engine is a bad thing that leads to reversion if the pressure in the exhaust is high. Wide LSAs are desirable on turbo engines. I was kinda wondering the same thing with respect to widest LAS seen on a roller cam.
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Re: What is the largest LSA you ever saw on a Mech roller
[Re: aarcuda]
#548910
12/08/09 02:46 PM
12/08/09 02:46 PM
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Joined: Aug 2004
Posts: 2,128
sweden
sshemi
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top fuel
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sweden
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Quote:
whats the advantage of wide LSA besides a nicer idle?
it gives a broader powerband
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Re: What is the largest LSA you ever saw on a Mech roll
[Re: blowndart]
#548911
12/08/09 02:50 PM
12/08/09 02:50 PM
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Joined: Dec 2005
Posts: 293
Kansas City Metro
mbogina
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A wide LSA does not affect the idle quality, the idle quality improves because of the reduction in overlap. The engine does not know or care what the LSA is, only the opening and closing events of the camshaft. You can adjust the overlap using the Intake duration, the Exhaust duration, the LSA, or all of the above in combination. Increasing LSA by 2 degrees reduces the overlap by 4 degrees total, but also moves every other timing event for the cam. The optimum overlap for any particular combo will "start" the drawdown of clean air on the intake stroke and "clean" the chamber of all residual exhaust gases on the exhuast stroke. Too much overlap leads to reversion, lazy throttle response, low dynamic compression, poor idle. Too little overlap sacrifices mid range torque and increases the sensitivity to detonation.
Be a Rebel- Break the Laws of Physics!
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Re: What is the largest LSA you ever saw on a Mech roll
[Re: mbogina]
#548912
12/08/09 03:07 PM
12/08/09 03:07 PM
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Joined: Oct 2004
Posts: 1,752
detroit area
moderncylinder
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what mike said  it always bothers me when guys start talking like wide lobe centers is high rpm, or for this motor only, or that motor,, the lobe sep is the distance between the lobes, doesnt tell you how much overlap you have,, or when you open and close the valves,,, which those are the parameteres that dictate where it all happens.. example,, im making this up as i type... open/close @.050, duration, center non-turbo/nat aspirated int 32/68, 280, 108 exh 78/30, 288, 114 sep 111 overlap 62 turbo/nitrous int 22/68, 270, 113 exh 78/20, 278, 119 sep 116 overlap 42 i didnt change the int close point just for reference though in a turbo you would,, but not in a nos application int 22/64, 266, 111 exh 84/20, 284, 122 sep 116 overlap 42 i changed the closing point on the int cause you have boost to fill the cylinder better in the intake stroke so you dont have to leave the valve open aslong in the comp stroke, though it depends on rpm, cid, and port area. i changed the exh open point cause you have more volume in the cyl in compression due to boost so there is more cyl pressure which leads to quicker/more effecient combustion, therefore gases will ne burnt quicker so you can open the valve a lil earlier.. pro stock int 28/72, 280, 112 exh 90/26, 296, 122 sep 117 overlap 54
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Re: What is the largest LSA you ever saw on a Mech roll
[Re: mbogina]
#548913
12/08/09 03:19 PM
12/08/09 03:19 PM
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Joined: Aug 2005
Posts: 759
Southington Ct.
turbobitt
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My line of questioning is because of my turbo application. I know that turbo applications have backpressure and as a result, will have no exhaust scavanging effect. I'm assuming that the LSA will depend on the duration of the cam to minimize overlap to some degree.
Another thing I would like to know if there is a noticable turbo spool-up difference with wider then normal LSA's. Example, if my cam is ground @ 113 LSA, what would the gains/losses be to a 115 LSA. How much is to much ?
1970 Challenger w/572 Hemi street car and my pride and joy.
1986 T-Type with 272 Stage 2 Buick V6 engine - True 8 second street car. Just updated the engine and put down 928 HP @ 35# boost to the ground on chasis dyno.
1976 Cee Bee Avenger Jet Boat - 460 Ford powered.
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Re: What is the largest LSA you ever saw on a Mech roll
[Re: turbobitt]
#548914
12/08/09 04:04 PM
12/08/09 04:04 PM
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Joined: Dec 2005
Posts: 293
Kansas City Metro
mbogina
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Too much is when you have reached the limits of the available cam cores, cores are only hardened to a depth of around .060, which limits the lobe lift, duration and LSA on that particular core. A billet core does not have the same limitations, so by playing with a little math you can go just about anywhere. Using Jeff's example above, a 266-284-116 has an overlap of 43 and when installed at 111 yields an IO 22, IC 64, EC 21 EO 83. By using the same lobes and increasing the LSA to 118, now you have 39 overlap, IO22 IC64 EC17 EO87. If you wished to keep the overlap constant but widen the LSA, the 266-284-116-43 could become a 270-288-118-43, or even a 274-292-120-43. The hard answer is to use whatever LSA suites the desired opening and closing numbers. Your cam grinder will advise you if your numbers will not fit his available core choices.
Be a Rebel- Break the Laws of Physics!
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Re: What is the largest LSA you ever saw on a Mech roll
[Re: mbogina]
#548915
12/08/09 06:18 PM
12/08/09 06:18 PM
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DFW
mr_340
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I've been over this with Mike before. Yes, the engine does see the opening and closing events, but to me either way you have four variables. IO, IC, EO, EC or Int Dur, Exh Dur, LSA, adv/ret Maybe it's easier to think about using Mike's preference. To me the cams are ground using the other parameters and that's what they give you in the catalogs. Maybe I'm more used to think of them in that way and haven't moved on to Mike's way? In 1998, I attended the SAE Motorsports Conference in Dearborn and they had a paper on restrictor plate engines in NASCAR. They were using LSAs in the 122 degree range. Sidebar - why do people like to put a period in front of the duration number? i.e. .286 duration. This started about ten years ago in magazines and it's plain wrong in my book. What, just over 1/4 degree of duration? I'd like to see that cam lobe. It would look like a stick on a round bar. 
Floyd Lippencott IV
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Re: What is the largest LSA you ever saw on a Mech roll
[Re: mr_340]
#548916
12/08/09 07:54 PM
12/08/09 07:54 PM
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Florida
Locomotion
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Quote:
Sidebar - why do people like to put a period in front of the duration number? i.e. .286 duration. This started about ten years ago in magazines and it's plain wrong in my book. What, just over 1/4 degree of duration? I'd like to see that cam lobe. It would look like a stick on a round bar.
lol
Since there isn't a "degree" key on the keyboard, I like to use the "asterick". I.E.: 263* @ .050"
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Re: What is the largest LSA you ever saw on a Mech roll
[Re: Locomotion]
#548918
12/08/09 09:12 PM
12/08/09 09:12 PM
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Joined: Nov 2004
Posts: 4,330
Lynchburg, VA
Leon441
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Lynchburg, VA
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I liked the 118 LSA. IT ran so much better than the 115 LSA. All the durations were the same. I fealt I could loose some intake but did not want to sacrifice the exhaust duration. Cam motion then ground me a 120 LSA but the Billet core had reached it limits and they suggested cutting the exhaust duration sense they fealt it was overkill. Well that cam hurt the performance.
This was a large displacement designed to kill small block.
My NA engine runs a large LSA and I feel that it hurts the performance. But, on the dyno we found engine performance is not the problem.
Leon
Career best 8.02 @ 169 at 3050# and 10" tires small block power.
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Re: What is the largest LSA you ever saw on a Mech roll
[Re: moderncylinder]
#548920
12/08/09 11:24 PM
12/08/09 11:24 PM
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Joined: Dec 2008
Posts: 1,200
UK
602heavy
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pro stock
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UK
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Quote:
what mike said
it always bothers me when guys start talking like wide lobe centers is high rpm, or for this motor only, or that motor,, the lobe sep is the distance between the lobes, doesnt tell you how much overlap you have,, or when you open and close the valves,,, which those are the parameteres that dictate where it all happens..
 , been here not so long ago.
Great post , well written. 
Last edited by 602heavy; 12/08/09 11:45 PM.
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Re: What is the largest LSA you ever saw on a Mech roll
[Re: mbogina]
#548921
12/09/09 12:31 AM
12/09/09 12:31 AM
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Joined: Jan 2003
Posts: 6,591
Canton, Ohio
Sport440
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Canton, Ohio
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Quote:
A wide LSA does not affect the idle quality, the idle quality improves because of the reduction in overlap. The engine does not know or care what the LSA is, only the opening and closing events of the camshaft. You can adjust the overlap using the Intake duration, the Exhaust duration, the LSA, or all of the above in combination. Increasing LSA by 2 degrees reduces the overlap by 4 degrees total, but also moves every other timing event for the cam. The optimum overlap for any particular combo will "start" the drawdown of clean air on the intake stroke and "clean" the chamber of all residual exhaust gases on the exhuast stroke. Too much overlap leads to reversion, lazy throttle response, low dynamic compression, poor idle. Too little overlap sacrifices mid range torque and increases the sensitivity to detonation.
Your response is Both True and False! Lobe Sep, Duration, and installed Centerline work together to move all those opening and closing events around that effect Desired performance.
So a Engine Will care what its "lobe sep" is, combined with its "Duration events".
LS and Dur. makes overlap a fixed number.
Change Either one, and you Can change a engines Idle characteristics.
ICL moves that overlap point forward or back from the TDC point of the piston between the Exhaust and Intake cycle of the piston.
So a engine will also care abouts its ICL too.
One thing you are Very correct about is the overlap part.
That is a Very important part of the combo. It will have a great effect. Its the Scavenging or Reversion part of the Combo. Its the 5th. stroke, of a 4 stroke motor.
Get it wrong and you can have a less then optimized motor for its set up. NA,Turbo,Blown,Nitrous,ETC. Get it Right 
Okay, what was I talking about! I was just making this up as i type.
One thing I know that we All can agree on is that
Valve Events are Effected by Lobe sep, Duration, and moved about TDC on the overlap cycle by Installed Intake centerline. And BDC with same said valve events mike
Last edited by Sport440; 12/09/09 01:13 AM.
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