How close is close enough
Thread Starter
Instructor
Joined: Jun 2014
Posts: 185
Likes: 10
From: S W pa. pa
How close is close enough
I installed my Isky cam the other day and attemped to check it with a degree wheel. My numbers didn't match the cam specs . Today I gave it an other try. This is what I came up with.
SPECS. @.050 lift intake
open -5 btdc 3 atdc
close 39 abdc 37 abdc
lobe lift .300 .297
dur. 214 214
exhaust
open 42.5 b bdc 45 b bdc
close -1.5 a tdc 2 b tdc
lobe lift .310 .307
dur. 221 223
On the intake, its 2 deg adv. correct??? On the ex. its 2.5 deg. late open and .5 deg late on closing Right???
How close is close enough?
I was going to call Isky , but I don't want to look stupid.
SPECS. @.050 lift intake
open -5 btdc 3 atdc
close 39 abdc 37 abdc
lobe lift .300 .297
dur. 214 214
exhaust
open 42.5 b bdc 45 b bdc
close -1.5 a tdc 2 b tdc
lobe lift .310 .307
dur. 221 223
On the intake, its 2 deg adv. correct??? On the ex. its 2.5 deg. late open and .5 deg late on closing Right???
How close is close enough?
I was going to call Isky , but I don't want to look stupid.
Tech Contributor
Joined: Aug 1999
Posts: 14,379
Likes: 6,390
From: At my Bar drinking and wrenching in Lafayette Colorado
Rather than attempting to degree off the open and close points, which makes you deal with the inaccuracy of the cam ramps, you should degree off lobe centerline. This "buffers" the inaccuracy of the start/stop points on the lobes and provides a much more meaningful data set. If you're unfamiliar with the centerline degree process, I believe CompCams has a good tutorial on their web site. Your cam spec carb should have the lobe centerline specs, which is what that's used for. 
Lars
Lars
Thread Starter
Instructor
Joined: Jun 2014
Posts: 185
Likes: 10
From: S W pa. pa
Rather than attempting to degree off the open and close points, which makes you deal with the inaccuracy of the cam ramps, you should degree off lobe centerline. This "buffers" the inaccuracy of the start/stop points on the lobes and provides a much more meaningful data set. If you're unfamiliar with the centerline degree process, I believe CompCams has a good tutorial on their web site. Your cam spec carb should have the lobe centerline specs, which is what that's used for.
Lars
Lars
I tried it your way and I came up with intake 111 lobe center
(112 spec.) and 112 ex. (right on the money) Lobe lift is still lacking .003 on both but close enough . I guess
Thanks
