2G Carb Question

I think I have other diagrams... Do the ones I posted work for your application?

 

I think the figure B that you posted from Walt's suggestion is the one that applies to my brass float with center seam. That is what I am measuring the 1 3/32" to - maybe I should be using a different float measurement with the brass float? The float is also mostly 'level' or horizontal which is a sort of 'rough, in the field kind of approximation'. Its how its been running for the last few weeks, but just double checking a few things as I do some troubleshooting and fine tuning. I am going to stay with that float level - but open to comments or suggestions.

 

Well, no pics but an update...I changed around plugs trying hotter and colder plugs, as well as varied the gap from .035 to 0.40" I have kept the tests with points and the slightly higher voltage flamethrower coil (with internal resistor) that I first installed a couple years ago. What I have found - the engine definitely likes the larger gap and the hotter plug. I also think the hotter plug will help keep the plugs cleaner when going to much higher elevation and the fuel mix turns rich.

So I am leaving in hotter plug, but now testing the jets size. Even with the hotter plug and larger gap, there was still the miss at constant med to high rpm. When driven quite a bit, the plugs will have a gray coating, which I was originally taking as good color indicator for air/fuel mix - but now wondering if the hotter plug was helping mask a too rich condition. The plugs weren't 'clean' - its just the powder was grey and not black. The one time I went up above 9000' they fouled quite a lot and the engine had some minor idle issues. So dropped a jet size from 49 to 48 - and everything seems to be getting much better. Only driven it around locally a bit, but no issues with pre-ignition that I can tell, or issues with running too hot etc. I had to play a bit with the timing to get rid of the high rpm miss: I am running initial at 6 (although it would probably like 8-10), but putting initial at 6 keeps the misfire away when at higher rpm. Haven't really driven it around much - hopefully tomorrow get a chance to put a few miles on it and then check plugs.

Its a slow process - but I feel like I am headed in the right direction. If I can get this settled I got a new pertronix ring to install. I never really got a chance to break in the transmission rebuild from last summer, but it feels like its starting to settle in and shift nicely. And I will say the Tera Low gears really are noisey at highway speeds!

 

This thread popped back up today and I realize I never gave a final update on this thread - so here it is:

The cj is running well these days, even at higher elevation (as many of my wheeling pics posted in that thread prove). After getting the carb tuned using the points, I installed the pertronix back in with no problems. As the above posts mention I think there was an issue with my old PV sticking open (which I eventually replaced), and the major problem was related to running too rich. I also eventually dropped down 47 jets, and things kept getting better. I actually think the 48 jets are perfect for here in Denver, but did not like going up to 13000'. The 47s work great in the mountains and get by here in Denver. I am thinking I might switch back to the 48s this winter as the high elevation trails are closed and I am also going to Moab which is a bit lower elevation than Denver. I realize the OEM specs suggest 49s are good for 5000' and 48's for 7500' and 47s for 10,000', but as this engine has a fresh rebuild with 252 comp cam grind and pertronix with flamethrower coil, it just seems to like a bit smaller jet.

In hindsight, I initially had too rich of a set-up and the idle screw got set to too high an rpm - maybe because that was needed to keep it running smoother as it may have actually initiated some mechanical advance which helped it to burn the fuel rich mixture. The too high rpm idle screw was offset by the idle screws basically being closed off and all fuel supply was bypassing the idle circuit and flowing via the main jets. At this 'idle', it liked 20 BTDC initial (maybe even more) but that didn't work with high throttle vac and rpm (predetonation issues). As I was able to lean it it out, and back off the throttle screw, that allowed the idle mix screws to be backed out and I was able to ensure the idle circuit was operating properly (gently turn the idle screws in to close and the engine chokes off). The engine also idles well now with much less initial timing - and that keeps the total max 'all in' timing below the predetonation threshold. (After getting this all figured out - I have now pushed the initial advance to as much as I can without pinging - that is 12-13 initial BTDC here in denver, and as high as 16 (haven't tried more) at the 10,000'+ elevations.)

I think low rpm tuning is can be a bit difficult as its easy to accidentally mask fuel supply tuning with a bit too much rpm at idle and bit more advance. And while its a 1970 carbuerated jeep with no charcoal canister etc - thus it will always have a bit more exhaust smell than a modern set-up - you can definitely smell (or maybe I should say not smell) the difference. I can drive it to work and when I go inside people don't automatically ask if I drove the jeep that day from my aroma!