I would start high

[G B.]

I experimented with a 30-30 GM cam in a 327 once to see if valve lash really made a significant difference. I changed the lash from .030" to the earlier 097 cam specs of .012" intake and .018" exhaust.

Afterward the idle setting had to be adjusted up from a solid 750 rpm (with 12-13 inches of vacuum) to a ragged 900 rpm. And, even then it only had 6-7 inches of vacuum at the higher idle speed!

I really didn't expect the increased duration and lift from the tighter lash to make that much difference. I didn't bother to make a test drive at those settings. I had seen enough in the garage.

[Clem Z.]

Re: I would start high

jerry you went too far the first shot as the specs we had from GM for racing with the 30/30 cam was .025/.025 back in the 60s. i think it has been posted on this site that the correct setting is .027/.027 by john h and duke w

[Duke W.]

Re: I would start high

I recommend .026"/.026" cold for the 30-30 using a specfic procedure for crankshaft orientation and specific valves to set at each crank positoon E-mail me or Hohn Hinckley if you want it.

The top of the clearance ramps are .020" above the base circle based on
a lift-crank angle diagram taken by Bill Clupper. This ramp height times
the ACTUAL rocker ratio at low lifts - 1.37:1 - yields .0274". Set them at a "loose" .026" and no-go on a .027" gage.

Rocker ratio adjustment yields .021"/026" for the LT-1 cam and .010"/.016" for the Duntov, but keep in mind that for '63 Chevrolet tightended the inlet spec to .008" to get a little more effective inlet duration, so '63s should continue at this setting and it is "optional" on earlier models for a bit more top end power.

Because of the LT-1's long ramps the 30-30 crank positioning algorithm should be used.
With the Duntov, you can set each cylinder at TDC, or do eight at TDC #1 and eight as TDC #6 as per the service manuals.

Duke

[Joe C.]

Re: I would start high

Jerry:

Check the archives, as I recieved some excellent advice from Duke and John H. last month. I had my 30-30 set too wide, which caused it to behave like a mild cam (smooth idle, super fast startup, good bottom end, 15 in-hg @ 800RPM).
After following the recommended procedure, I have a totally different animal (lumpy idle, somewhat harder to fire up, less bottom end, screams at high R's, 10 in-hg @ 900RPM).

Here is the procedure. Set int/exh @ .027" cold. First, index your harmonic balancer @ 90 degree intervals:

Cyl @ TDC (power stroke): 1 8 4 3 6 5 7 2
Adjust intake****************: 2 1 8 4 3 6 5 7
Adjust exh.******************: 8 4 3 6 5 7 2 1