The Cruise timing is only an issue if you want to squeak out some fuel economy.
It has happened that after installing an overdrive, the engine actually loses fuel economy, because the new rpm is too low for the cam, and or the engine is NOT getting the ignition advance it needs.
I my experience, cruising at 2240 for years and years with my overdrive, I know that my engine likes timing deep into the 50s. Your results will vary. With the previous cam it was Ok with less.
Here are the Advertised durations of my two Hughes Cams, first the previous HE2430AL, then
the current HE3038AL;
1) 270/116/111/276/110+1/53,52Effective/Ica of64*
2) 276/116/103/286/110+4/61,58Effective/Ica of64*
Intake/compression/power/exhaust/ LSA/ovrlap/Ica
Cam 1 made fantastic fuel mileage, that Cam 2 couldn't touch.
Notice the colored numbers.
Cam 1, has 7.8% more degrees spent in power extraction, and has 8* or less overlap, or 89.6% as much.
I can tell if a cam is likely to make good fuel mileage by adding the compression and extraction degrees together. Cam 1 has 227, and cam 2 has only 219. No matter where you time the cam; you can trade a few degrees this way and that with cam-timing; but the totals will always add up to 227 and 219.
One might not think that such a small change would be a big deal, but when you factor in the overlap, that's when if goes to heck.
With Cam 1)
I could run a final drive of 3.23 x .71 x.78= 1.79, which is 65=1460, I mean the engine had no problems pulling that; but I could not get the timing up. She wanted 60 degrees, which consistently allowed the smallest throttle opening. My power curve had been established at .78* per 100 from 1200 to 2800, and 14* initial. So at 2000rpm, that came to 24*. To that, my Vcan was adding 20, for a total of 44*. So I was still 16* short. But at 1460 there was just no way to satisfy it.
So I went and got me a standalone timing delay box with a range of 15*, for a total of 59*@2000 rpm , but 2000 rpm was 90 mph! So I had to do something!.
I ditched the OD box, and replaced it with a Commando box, and got 65=2060; badaboom. And that is how I get fantastic fuel mileage with cam 1.
With Cam 2)
I chose a cruise speed of 65=2240 (manual trans); now using 3.55s and the .78 GVod for a final drive of 2.77
1) any slower and reversion was an issue and I couldn't control the AFR., and
2) it is the lowest rpm I could get the cruise timing up close to where it needed to be
3) but with the extraction reduced to 103 from 111, and the rpm up a bit; 2240 versus 2060, there was no way she would give me the mileage that I had been enjoying for the previous 4 years. So since 2005, I have been waiting for Cam 2 to die ...... but she's like the Energizer bunny...........
My car was a DD for years, racking up around 120,000 miles in less than 10 years, so to me, fuel economy was a really big deal.
But if you don't care about fuel economy.... then optimum cruise-timing is meaningless.
