How do you determine LSA from a Cam Doctor sheet?
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09-07-2007, 11:31 AM
#9
Originally Posted by Tram
Maybe where it says Centerline: 111.3? 
The LSA is the distance between those two centerlines, but in camshaft degrees not crankshaft degrees. Therefore 111.3 BTDC for the exhaust plus 111.3 degrees ATDC for the intake equals 222.6 degrees. You have to divide that by two and you get your LSA of 111.3. Both intake and exhaust centerlines are the same so the valve events are measured assuming the cam is installed "straight up" with no advance or retard.
Say we changed the cam timing a bit and made the Intake Centerline (ICL) 110.3 degrees ATDC. That would mean the Exhaust Centerline (ECL) would now be 112.3. Add em up and divide by two and you still get 111.3 LSA.
09-07-2007, 11:50 AM
#11
Originally Posted by KCS
That's not the LSA, that is the centerline of the intake/exhaust lobe.
The LSA is the distance between those two centerlines, but in camshaft degrees not crankshaft degrees. Therefore 111.3 BTDC for the exhaust plus 111.3 degrees ATDC for the intake equals 222.6 degrees. You have to divide that by two and you get your LSA of 111.3. Both intake and exhaust centerlines are the same so the valve events are measured assuming the cam is installed "straight up" with no advance or retard.
Say we changed the cam timing a bit and made the Intake Centerline (ICL) 110.3 degrees ATDC. That would mean the Exhaust Centerline (ECL) would now be 112.3. Add em up and divide by two and you still get 111.3 LSA.
The LSA is the distance between those two centerlines, but in camshaft degrees not crankshaft degrees. Therefore 111.3 BTDC for the exhaust plus 111.3 degrees ATDC for the intake equals 222.6 degrees. You have to divide that by two and you get your LSA of 111.3. Both intake and exhaust centerlines are the same so the valve events are measured assuming the cam is installed "straight up" with no advance or retard.
Say we changed the cam timing a bit and made the Intake Centerline (ICL) 110.3 degrees ATDC. That would mean the Exhaust Centerline (ECL) would now be 112.3. Add em up and divide by two and you still get 111.3 LSA.
09-07-2007, 11:59 AM
#12
Originally Posted by Tram
I have no idea.. I just took a guess based on what Predator Z said.. 
I'm just as much as newb as you are..
I'm just as much as newb as you are..
09-07-2007, 12:10 PM
#13
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Originally Posted by 5.3LJimmy
I'm not a newb. I was looking to verify the method I was using w/o telling everybody the way I was doing it. B/c people will post yeah you're doing it the right way w/o even knowing for sure. Kinda like the way you posted the answer to my question but didn't know what you were talking about... perfect example.
My sincerest apologies.. I didn't mean to ruin your non-newb reputation..
I said "maybe."
I also openly admitted I was a newb..
I have no idea, Pred Z said 111.3 so I looked at the sheet and found 111.3.. "maybe."
09-07-2007, 12:17 PM
#14
Originally Posted by Tram
Wow.. Someone tightened their tie a bit too tight this morning..
I said "maybe."
I also openly admitted I was a newb..
I have no idea, Pred Z said 111.3 so I looked at the sheet and found 111.3.. "maybe."
I said "maybe."
I also openly admitted I was a newb..
I have no idea, Pred Z said 111.3 so I looked at the sheet and found 111.3.. "maybe."
09-07-2007, 12:20 PM
#15
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No sweat.. I guess I could see where it would look like I was trying to be a dick and saying "Maybe where is says..." and trying to make you look like an idiot..
That was not my intention.. I wasn't trying to post incorrect information, I only meant "Maybe where it says 111.3" in the most humble of ways..
I would edit it, but it has been quoted which won't do much good..
No worries man..
That was not my intention.. I wasn't trying to post incorrect information, I only meant "Maybe where it says 111.3" in the most humble of ways..
I would edit it, but it has been quoted which won't do much good..
No worries man..
09-07-2007, 01:11 PM
#16
TECH Senior Member
Originally Posted by KCS
That's not the LSA, that is the centerline of the intake/exhaust lobe.
The LSA is the distance between those two centerlines, but in camshaft degrees not crankshaft degrees. Therefore 111.3 BTDC for the exhaust plus 111.3 degrees ATDC for the intake equals 222.6 degrees. You have to divide that by two and you get your LSA of 111.3. Both intake and exhaust centerlines are the same so the valve events are measured assuming the cam is installed "straight up" with no advance or retard.
Say we changed the cam timing a bit and made the Intake Centerline (ICL) 110.3 degrees ATDC. That would mean the Exhaust Centerline (ECL) would now be 112.3. Add em up and divide by two and you still get 111.3 LSA.
The LSA is the distance between those two centerlines, but in camshaft degrees not crankshaft degrees. Therefore 111.3 BTDC for the exhaust plus 111.3 degrees ATDC for the intake equals 222.6 degrees. You have to divide that by two and you get your LSA of 111.3. Both intake and exhaust centerlines are the same so the valve events are measured assuming the cam is installed "straight up" with no advance or retard.
Say we changed the cam timing a bit and made the Intake Centerline (ICL) 110.3 degrees ATDC. That would mean the Exhaust Centerline (ECL) would now be 112.3. Add em up and divide by two and you still get 111.3 LSA.
BINGO
09-07-2007, 06:04 PM
#17
Originally Posted by 5.3LJimmy
That's the way I always did it, but thunder wrote 11.27 for the LSA on the sticker they put on the cam box. I guess they are trying to add a little flare to the measurements. Thanks KCS.
09-08-2007, 09:25 AM
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Originally Posted by 1989GTA
What is the advertised lift for the cam lobes? Just wondering how close they were.
Last edited by JPH; 09-08-2007 at 09:31 AM.