Cam Specs explanation
07-16-2003, 10:27 AM
#1
Teching In
Thread Starter
Join Date: Oct 2002
Location: Austin
Posts: 12
Likes: 0
Received 0 Likes
on
0 Posts
Cam Specs explanation I think some good info for people just getting into LS1's is what those numbers mean for cam specs. I get mixed up myself so I figured I'd post here to get the answers.
Example: I have the TR 227/224 .569/.563 114 cam.
the 227 number is the intake valve duration
the 224 number is the exhaust valve duration
the .569 value is the intake lift
the .563 value is the exhaust lift
the 114 is the LSA(lobe separation angle)
My questions-
1) for the valve duration numbers, what exactly do they represent? i.e. is it 227 degrees of duration, or how does this correlate with crankshaft/cam revolution(s)?
2) the valve lift numbers, is that in inches and how is it measured? (from the base circle to the top of the lobe?)
3) for the LSA, I realize that it is the separation between the intake and exhaust, but like question #1 how does that correlate to crank/cam revolution?
4) What are the stock specs for a cam in an Fbody or Ybody to compare these to? It would be nice to see the difference between a stock cam and the aftermarket.
Thanks in advance!
Tim
Example: I have the TR 227/224 .569/.563 114 cam.
the 227 number is the intake valve duration
the 224 number is the exhaust valve duration
the .569 value is the intake lift
the .563 value is the exhaust lift
the 114 is the LSA(lobe separation angle)
My questions-
1) for the valve duration numbers, what exactly do they represent? i.e. is it 227 degrees of duration, or how does this correlate with crankshaft/cam revolution(s)?
2) the valve lift numbers, is that in inches and how is it measured? (from the base circle to the top of the lobe?)
3) for the LSA, I realize that it is the separation between the intake and exhaust, but like question #1 how does that correlate to crank/cam revolution?
4) What are the stock specs for a cam in an Fbody or Ybody to compare these to? It would be nice to see the difference between a stock cam and the aftermarket.
Thanks in advance!
Tim
07-16-2003, 11:00 AM
#2
Teching In
Join Date: Jul 2003
Posts: 3
Likes: 0
Received 0 Likes
on
0 Posts
Re: Cam Specs explanation 1) weighted question... is the .050" duration #? If it is, then it is 227 degrees of a circle from .050" open to .050" closed... so for 63% of the cam revolution, the intake valve is above .050" lift.
2) there are two measurements of lift...
lobe lift - the actual height of the lobe itself... this # assumes 1:1 rocker arm ratio
valve lift - determine this by the rocker arm ration * lobe lift...
so on a 1.71:1 RAR for this cam, you'll have .569" of lift on the intake valve. the actual lobe lift of that intake is about .333"
2) there are two measurements of lift...
lobe lift - the actual height of the lobe itself... this # assumes 1:1 rocker arm ratio
valve lift - determine this by the rocker arm ration * lobe lift...
so on a 1.71:1 RAR for this cam, you'll have .569" of lift on the intake valve. the actual lobe lift of that intake is about .333"
07-16-2003, 11:02 AM
#3
Teching In
Join Date: Jul 2003
Posts: 3
Likes: 0
Received 0 Likes
on
0 Posts
Re: Cam Specs explanation btw... if you're comparing this to a stock cam, it is kinda hard to determine what will actually make good power... i'm assuming that you can buy this cam (just re-read it... that TR cam is good, btw) so that it must make power over stock, but in a comparison issue, you'd need a cam card for any real in depth discussion.
