First, I think it needs to be stated that getting a TR6 through Smog II is the equivalent of the Biblical "passing a camel through the eye of a needle." However, there are a number of things you can do to help get your 6-cylinder car through.
1. Change the engine oil just before you go to test. Fresh 20/50 seals better than any oil with 50 or more miles on it. The idea is to reduce hydrocarbons (HC), and with the TR250/6’s very poor bore to stroke ratio it needs all the help it can get.
2. Put in a new set of spark plugs, gapped at .032".
3. Convert from carbon core ignition wires to the solid core (metal) type.
4. Adjust the valves looser by .005 from normal settings. This one is a little more diffficult to to understand, but about .005" degrees of valve clearance on the ramps of the camshaft converts to about 20 degrees less cam timing at the base of the ramp where a good deal of the pollution occurs as liquid fuel that has puddled in the manifold runs past the partially closed valve at high vacuum.
5. Make sure all the correct smog equipment is there and working, particularly the PCV diaphragm, as you won’t get by the machine without it.
6. Retard the ignition timing about 3 degrees to help reduce the NOX emissions.
7. Adjust the carbs lean enough so that the engine should die when you lift a carb piston with a knife about 1/32 to 1/16 of an inch.
8. Drive it on the freeway at approximately 60 mph. For about 10 miles before you go to the text in order to be sure that the engine is at full operating temperature.
9. Use a low-restriction air cleaner set. Hellings has one about 1/2" thick with metal wire for a filtering medium. It will only filter out large rocks, but it flows very freely.
10. Run the fuel tank down as far as possible and refill it just before the test. Fuel has a ‘half-life’ and it does not burn well if it has been in the tank for 90 days or more.
None of the above are guaranted to get you through the test successfully, but they will give you a fighting chance. Good Luck!