22R Distributer Timing ?
 

I have a 1983/4 Toyota Pu with a 22R & a Weber Carb. The timing was set on this one when it had the original Carb. I installed an Lc Eng Weber 32/36 with a spiral adapter. The engine runs real well, but I'm working on mpg & possibly a little better performance. It appears the timing is on at 12 degrees BTDC, not 5 degrees per the manual. Could someone help me understand if this is good or should I lower the timing ? Originally, this was a pu chassis then converted to an RV. Clearly, I'm a non-mechanic. I have worked on my vehicles all my life, but I'm better with the R&R stuff. Thanks for any help.

Does you distributor have vacuum advance? If so, make sure the vac canister holds vacuum. Likely the 5 degrees is with the vac advance disconnected. You may be reading 12 with vac advance connected. Confirm disconnected and plugged when you take the reading and idle speed is where it’s supposed to be. If idle speed is too high, mechanical advance begins to come in and adds to your initial. If your timing is too far advanced, you will get detonation or “pinging”. Modern engines have knock sensors to retard timing and compensate for that. Every ping or knock is a combustion event losing power and efficiency.

I’ve done lots of experimenting with timing curves and carbs on my old musclecar, and i’d say very likely you may be able to improve your mpg with more advance and leaner jetting but you really need an air fuel meter if you want to go down that road and collect data.
If you have a vacuum gauge, you can set the idle mixture screws on the carb for highest vacuum reading and then maybe back off slightly(a little richer) to smooth out the idle. A rich idle will run smooth but you don’t know what you are giving up. A leaner idle will yield better mpg than a rich one.

I don't know if everything is as tight as it should be. I did measure the timing with the vac adv closed off both ways & it was still at about 12. The engine runs well, but I just checked the mpg again & it was at about 12. Previously, I had as much as 18.5 mpg. It sounds like I should set the timing between 5 & 8 degrees & re-tune the carb using the weber procedures. There is a third screw for idle speed screw on the weber that I don't know what to do with. Are you familiar ?

https://www.cjclub.co.il/files/Weber3236adjust.pdf
did these instructions cone with the carb?

i don’t have one but carbs all do the same thing.

I didn't, but I did find it yesterday. I'll dig into it deeper shortly. Thanks for the share. My sense is that I am ok with the basic carb adj, but not the other platform issues.

id recommend just going down between 0-5 degrees btdc. that is what most manuals will say