[DeTomaso] Spark advance

[Thomas Tornblom]

I have a bucking issue while cruising at low load and low rpms, 
1000-1500 rpm.

Looking at my spark tables I see that the advance varies from 24° to 36° 
in this region, depending on load and rpm, and I suspect that this is at 
least part of the problem.

I checked an old log, and I see that I had 33.5° at 1000 rpm and 20% 
load (VE). That seems a bit excessive to me.

When I had the old flat tappet Crane cam (133052, 284H12), and open 
chamber heads, I was using the stock 5.0 Mustang spark tables, which was 
even more aggressive at low rpms, and it was silky smooth. I could 
easily putter around town at 25 mph in 5:th.

I don't remember if it behaved as good when I installed the closed 
chamber 2V heads, but I know I had to retard timing at higher rpm as it 
would ping even when cruising at low load. There were places that called 
called for 40° of advance.

After it ate a lobe in Italy, I built a new engine with a Crane 529801 
hydraulic roller, and it has been bucking on and off since then.

Does anyone have a spark table from a similar engine that might work as 
a starting point?

Or what would a reasonable spark advance be for around 1000-1500 rpm 
light cruising?

Cheers,
Thomas