Camshaft LSA VS LCA
Thread Starter
On The Tree
Joined: Dec 2022
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Camshaft LSA VS LCA On all cams you have LSA and LCA.
Ok so LSA is lobe separation angle is between inlet and exhaust lobes and LCA lobe centre line angle of each of the inlet and exhaust.
So a cam with a straight up 112 112 LCA has a single LSA of 112 LSA.
But these days cam manufacturers like to run a split cam LCA by advanceing the inlet LCA by 4 degrees.
like comp cams for instance.
They will advertise their cams with a 113+4 LSA.
So the inlet lobe is on a 109LCA and the exhaust is on a 117LCA to achieve a 113LSA.
My question is what is the advantage of doing this.
Would it be better to have just a straight up 113LSA or is it better to have the split 109lca and 117lca to give a 113LSA.
Obviously having a split LCA has some sort of affect on engine performance.
So what is it exactly?
Ok so LSA is lobe separation angle is between inlet and exhaust lobes and LCA lobe centre line angle of each of the inlet and exhaust.
So a cam with a straight up 112 112 LCA has a single LSA of 112 LSA.
But these days cam manufacturers like to run a split cam LCA by advanceing the inlet LCA by 4 degrees.
like comp cams for instance.
They will advertise their cams with a 113+4 LSA.
So the inlet lobe is on a 109LCA and the exhaust is on a 117LCA to achieve a 113LSA.
My question is what is the advantage of doing this.
Would it be better to have just a straight up 113LSA or is it better to have the split 109lca and 117lca to give a 113LSA.
Obviously having a split LCA has some sort of affect on engine performance.
So what is it exactly?
TECH Enthusiast
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Advancing the cam by 2-4 degrees has been shown to gain a significant amount of low end torque without affecting top end power in street engines that generally red-line at 6000-6500rpm. The reason for this is you effectively increase your engines Compression ratio by having the intake valve close a bit sooner, trapping a bit more air for your compression stroke. Some also claim that advanced cams give better driveability.
If you were going to spin the engine faster, running consistently in the power band at 7000+rpm, installing the cam straight or even a hair retard can give better high rpm breathing and more power.
If you were going to spin the engine faster, running consistently in the power band at 7000+rpm, installing the cam straight or even a hair retard can give better high rpm breathing and more power.
Thread Starter
On The Tree
Joined: Dec 2022
Posts: 172
Likes: 25
Advancing the cam by 2-4 degrees has been shown to gain a significant amount of low end torque without affecting top end power in street engines that generally red-line at 6000-6500rpm. The reason for this is you effectively increase your engines Compression ratio by having the intake valve close a bit sooner, trapping a bit more air for your compression stroke. Some also claim that advanced cams give better driveability.
If you were going to spin the engine faster, running consistently in the power band at 7000+rpm, installing the cam straight or even a hair retard can give better high rpm breathing and more power.
If you were going to spin the engine faster, running consistently in the power band at 7000+rpm, installing the cam straight or even a hair retard can give better high rpm breathing and more power.
My question is aimed at why do cam manufacturers grind the cams with a split LCA to give LSA.
What benefits are achieved by doing this.
Wouldn't just grinding the cam on a single LCA /LSA give the same or better results or does it change the torque and power curve?
TECH Enthusiast
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Yes I know about installing cams advanced or retarded and what that does to power and torque.
My question is aimed at why do cam manufacturers grind the cams with a split LCA to give LSA.
What benefits are achieved by doing this.
Wouldn't just grinding the cam on a single LCA /LSA give the same resame or does it change the torque and power curve?
My question is aimed at why do cam manufacturers grind the cams with a split LCA to give LSA.
What benefits are achieved by doing this.
Wouldn't just grinding the cam on a single LCA /LSA give the same resame or does it change the torque and power curve?
Thread Starter
On The Tree
Joined: Dec 2022
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So I doubt that is the case.
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TECH Enthusiast
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Just believe whatever you want to believe. They grind the recommended advance into the cam just to mess with you, thats why.
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My thinking is it simplifies install for people who aren't tech savvy enough to degree a cam with an indicator and degree wheel. So if they install it "straight up" by aligning timing marks, the 4°, or whatever degree, advance is there....
Thread Starter
On The Tree
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I doubt that as you still need to degree the cam the alignment for TDC.
TECH Enthusiast
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90% of the time you don't, just assemble dot to dot. That tenth time you somehow wind up with 10 degrees of retard in the cam wondering why the engine runs like ****.
Most people are decent mechanics but if you're building an engine in your carport the cam company is trying to make the process mistake resistant. I think the easiest way to do that is make the system such that it will be as good as possible even if you can't adjust it, hence locked timing set and advance ground into the cam.
Most people are decent mechanics but if you're building an engine in your carport the cam company is trying to make the process mistake resistant. I think the easiest way to do that is make the system such that it will be as good as possible even if you can't adjust it, hence locked timing set and advance ground into the cam.
Thread Starter
On The Tree
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All I've been able to work out is by running plus 4 advance on inlet centre line.
the cam has the inlet open close is advanced 4 degrees and exhaust open close is retarded 4 degrees to maintain a poticular lsa or lobe separation targeted.
that's all I've found. And worked out.
the cam has the inlet open close is advanced 4 degrees and exhaust open close is retarded 4 degrees to maintain a poticular lsa or lobe separation targeted.
that's all I've found. And worked out.
TECH Senior Member
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From: Central Cal.
You can't advance intake and retard exhaust on the same cam. If it is advanced 4 degrees, BOTH intake and exhaust are advanced.
Only by increasing the LSA in the grind can both happen
Only by increasing the LSA in the grind can both happen
In most cases, modern CNC cam grinders are dead nuts. There is nothing to doubt. Degreeing is a double check of how close the advertised specs are to actual specs. Also for peace of mind for the buyer. However, sometimes in some special situations, the owner may want to advance, or retard cam timing. In reality, there's nothing you can do about it if the cam is ground a couple of degrees off, unless you buy an adjustable timing set, AND know how to use it.