[Fot] Mystery cam

[Bill Babcock]

Damn, I’ve been staring at this too long. Of course you’re right. I bit the bullet and pulled off the rocker arms to do it right and now the numbers are even more confusing. 


> On Jun 14, 2016, at 1:08 PM, Duncan Charlton <duncan.charlton54 at gmail.com> wrote:
> 
> Hi Bill,
> 
> If I understand you right, you measured lift at the valve itself, in which case it looks to me that you did the rocker arm equation backwards.  0.050” lift at the cam should see a greater movement at the valve, not a lesser degree.
> 
> I hope you ended up with a Tiltech cam — that’s what I would choose if I could get one today.
> 
> Duncan
> (Texas)
> 
>> On Jun 14, 2016, at 12:11 PM, Bill Babcock <ponobill at gmail.com> wrote:
>> 
>> I’m building a new motor for Peyote from the bits of it’s previous engine. I discovered the front main bearing cap was cracked in half when I decided to freshen the motor. I’ll work on replacing the cap later—maybe get a billet one made, but in the meantime I’ve run into a minor problem. I don’t know for sure what cam I have or how it should be set.  Tony Garmey says it’s a BFE cam, but I can’t find any specs for those and can’t get ahold of Ken. 
>> 
>> I ballparked where I think the cam might want to be and got this for measurements: 
>> 
>> Reading the Intake and exhaust valve movement from the spring retainers I use 0.033” as the open/close height which is .050/1.45 which as I recall is the ratio of the stock rockers”
>> Intake open .033 @ 36 BTC
>> Intaake close .033” @ 76 ABC
>> Exhaust open .033” @ 76 ABC
>> Exhaust close .033” @ 42 ATC
>> 
>> By my calculations that gives:
>> Intake duration 292.0 degrees
>> Exhaust duration 298 degrees
>> Intake lobe center 110.0 ATC
>> Exhaust lobe center 107 BTC
>> Overlap 78
>> Lobe separation angle 108.5
>> 
>> Pretty sure this isn’t exactly where it needs to be. I have a vernier sprocket so I can adjust the timing precisely. My questions are:
>> 
>> What cam is this?
>> Where should it be set?
>> How much advance?
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>