I think you're having a lot more fun than me. I'm struggling with cam
timing on my motor and I need a sanity check.
Here's the problem. I've got a kind of unknown cam in Peyote--the guy who
could give me some hints on the specs is incommunicado for a few weeks. I'm
compounding my problem by installing a vernier cam wheel, so there's no
marks to start from. I set up a degree wheel and dial indicator, and started
measuring. I assumed that the timing should be set with .050" lift, and
since I'm coming straight from the cam follower and assume a 1.4 rocker
ratio, I'm using .036" lift.
I tried setting it up with 50 degree BTDC inlet open and got some very
screwy numbers. So I checked the centerline of the intake and exhaust cam
lobes and decided to start with 110 degrees ATDC. After a bit of fiddling I
measure:
Intake opens 33 degree btdc
centerline 112 degrees ATDC
Intake closes 65 degress ABDC
which gave me
exhaust open 72 degrees BBDC
Exhaust CL 115 degrees BTDC
Exhaust closes 25 degrees ATDC
and that calculates to:
Overlap 58 degrees
Intake duration 278
Exhaust duration 277
calculated centerline intake: 106 ATDC
Calculated exhaust CL: 113.5 BTDC
Weird. there's no way the exhaust should close that early and the intake
opening is about good for a street engine.
So I tried again, setting the centerline of the intake cam to 100 degrees
I got:
Intake
open 37 degres BTDC
CL 98 degrees ATDC
closes 57 degrees BBDC
exhaust
opens 79 degrees BBDC
CL 120 degrees
closes 17 degrees ATDC
which calculates to
Overlap 54 degrees
Intake dur 274
exhaust dur 276
Inlet cl 100 ATDC
exhause cl 121 BTDC
I'm flummoxed. Can't figure out what I'm doing wrong. Any ideas?
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