[Fot] GT6 cam timing advice

[Rick Parent]

Hi Jim,
103-104 at the lobe is where you want to be. The 270 would be at the valve.
Hope this helps?
Rick 

    On Monday, April 18, 2016 6:47 PM, "toodamnfunky at comcast.net" <toodamnfunky at comcast.net> wrote:
 

 FoT
I'm building a motor for a club member and am having some difficulty with cam timing specs. It's an APTcam and the spec sheet they provided is not only nonsensical but it has some of the data crossed out and some of the numbers hand written in. No real usable data on timing it for it's best performance. At best it's really more of a fast road cam. I didn't spec the cam or buy it. It has 108 degree lobe centers, .280 lobe lift and a duration of 270 degrees at .020 lift. The data sheet says Time to ATDC 103 - 104 degrees and it's supposed to have.071 lift at TDC. This cam won't do both.When I time it to 104 degrees ATDC at full lift I get 9 degrees BTDC at .071, which also translates to 20 degrees BTDC at .050 liftwhich to me sounds more reasonable. I've contacted APT twice now and the first answer was a lot of jibberish and they haven't answered the second inquiry yet regarding the math that will not work.What I don't want to do is inadvertently RETARD the cam. I'm used to working with .050 for valve opening but APT doesn't consider .050 an open valve. Any advice would be more than welcome.jim g
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