Thanks for all the responses.
Here's the project: I'm compiling a list of diesel tractors to assess their possibility for woodgas conversion. Old diesel tractors are plentiful and cheap; the conversion is fairly simple although more work than a gasoline conversion.
It's much easier if the compression is already low enough (17:1 or less). Most tractors from the 60s and 70s are right in the sweet spot. I'm still working down the list. There are a lot of old tractors out there.
To run on woodgas, it needs an ignition system in place of the injector pump. You might also want hardened valve seats, but I'm not sure if this is required on a slow speed tractor.
Power should be around 80% or better of the diesel output. Because of the high compression, you'll get more power from the same woodgas than a comparable gasoline engine.
Here's some examples from the responses I got.
Paul McCombie's Case 780 has 17:1 compression. This should work on woodgas. It's right at the limit, which means it's a good test to verify the India Institute's results.
David Baillie's Case 830 has 15.0:1 compression. Should work fine.
Jeff Davis' old Belarus had 16.0:1 compression. Should work fine.
Jeff Davis' old JD 510 is over the limit at 17.3:1
Marvin's Deutz D 4006 is also too high, 19.0:1
Wayne's Farm Pro 2420 is too high, 22.0:1
Wayne's JD 2130 should work OK, at 16.8:1. I think Wayne tried this unsuccessfully.
- Wayne's Fordson Major should work OK at 16.0:1, in fact here's a video of one running on woodgas!
I'll keep adding to the list, here's the actual spreadsheet I'm keeping.