[Fot] Cam timing mystery

[Marcel Van Mulders]

If the cam is  symmetrical and inlet and exhaust timing have the same
duration, the cam is 20°- 56°   56° - 20° at 0.050" and the theoretical
installation figure (inlet valve no 1 at maximum lift) is 108° ATDC(=
position of the crankshaft). If you want to advance the cam by 4°, the
installation figure is 104° and the timing 24-52 60-16.
Marcel

-----Oorspronkelijk bericht-----
Van: Fot [mailto:fot-bounces at autox.team.net] Namens Larry Young via Fot
Verzonden: woensdag 14 december 2016 02:00
Aan: Bud R; FOT at autox.team.net
Onderwerp: Re: [Fot] Cam timing mystery

Bud,
You do not need a Cam Cards or Cam Doctor to determine what you need. 
You can measure everything with a dial indicator and degree wheel. I have a
couple of pages at my website and a spreadsheet that may help.  I agree with
Bud that 4 degrees of advance is probably a good starting point.
  - Larry
http://tildentechnologies.com/Cams/Tip_DegreeCam.html

On 12/12/2016 3:14 PM, Bud R via Fot wrote:
> List,
>
> I have an inherited cam (came with the car) that has no markings
whatsoever so I don’t know what brand it is exactly (although it’s close to
an Elgin 7708-12 grind for 5500-7500 rpm road race cam @ 12:1 CR). I had it
ground and nitrided and the cam grinder told me the duration was 256 degrees
at 0.050 inches, and the cam lift is 0.350. The lobe separation angle is
108.5 degrees. I’m going to use 1.55 rockers.
>
> I did not and probably cannot get a cam card from the grinder, it’s a long
story.  So I’m trying to figure out what the cam timing should be since he
never told me what it should be.
>
> Any one running a similar cam that could tell me at least a ballpark for
timing this cam? I don’t have access to a Computer Doctor setup to figure it
out, the grinder supposedly had one but either didn’t use it or didn’t tell
me.
>
> If there’s a plus/minus range of 6 degrees retard/advance for cam timing
from TDC can I start somewhere in the middle to see what works best? Once
the engines done it will go on a dynamometer for break in and tuning, but
I’d like to get it dialed in better before that. Where to start?
>
> Thanks
> Bud
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