It starts pretty easy now. The partially grenaded starter was just functional enough to fool me a bit. It can take some turning first thing in the morning to get it to catch, but once it's good it's good. If it's really cold (like this morning at -2) it will occasionally want fuel on top of the choke in the form of the accelerator pump being worked a bit. I haven't driven it since yesterday's tuning extravaganza, but I have a feeling it'll behave quite nicely going forward.
Speaking of yesterday... What a day! Long and productive, met some pretty awesome guys, and passed out the second my head hit the pillow! I left the house around 6:45 to head down to AirRandy's shop to meet up with Ricardo. When I get there, BigCity was already half may through removing his tranny due to a crappy input shaft bearing. Ricardo spent all day dancing beween the two bays helping everyone get their jobs accomplished, Randy was in and out, and I helped out where I could with the transmission work when priorities dictated.
We started with a baseline. Set the timing (I must not have tightened the distributor clamp all the way out of paranoia from the first one breaking, as it had wandered back to 7º), checked the compression (my tester was found to be broken after my attempt lead to a freak out session, and the compression was found to be very healthy with a good tester), then installed the O2 sensor. I had Bud's install a bung on my new exhaust when I got that taken care of, and the guy forgot to weld it in until after the exhaust was already in the truck. As a result, it was a little off center, and the pipe prevented installation of the sensor... Due to a complete lack of clearance, the exhaust had to be mostly removed from the truck, and a dremel was used to clean up the problem. Once rectified, the exhaust was reinstalled, we wired in the rest of the wideband harness, plumbed it through the kick vents, and we were off to the races!
Unfortunately, I wish to note here that due to time constraints and the fact that I had earballed it pretty close to start, photo documentation did not really happen... Sorry. If this proves to make a significant difference, we'll do someone else's truck and do it better with photos.
First things first, we set the idle. 650 RPM, 14º advance, and 14:1 AFR. AFR at idle is controlled by the idle mixture screw. You can get 14:1 with a 55 slow as well as an 85 slow, the only difference is the number of turns.
Next, we took it for a baseline spin. Jets to start were 60 primary slow, 118 primary main, 70 secondary slow, 200 secondary main (this was known to be very rich), and 80 power. The primary slow was dead on in the 16-17 range. Couldn't ask for anything better. Primary main was a skosh rich, secondaries were close and really rich (as low as 10), but without getting the primaries in, secondaries and power are a best guess scenario.
We rolled back into the shop, and I set about changing the jets. I forgot my jet grabber screw driver, and had to partially disassemble the carb for every change... The next primary main I had down was a 114, and the next secondary main down was a 180. Those were swapped and we went for another run. We discovered at this point that there is a delay in the wideband, and this combined with lots of closely spaced hills make for a really tough time nailing down circuit transitions... Eventually, it was decided that both mains were now a touch lean with primary coming in around 18-19 and secondary around 14-15. Power was still coming in 10-11.
Back to the shop, I reamed the 114 to a 116 and reamed the 180 to a 185, and changed the power valve out for a 60. Put it all back together and went for a run. This time things were NOT reading right... I was getting 19:1 at idle and pretty much through the primary progressions... Really not cool. At one point it stuttered and since the fuel gauge was on E (an exceedingly common state so far in my LC ownership), we stopped at the gas station. I couldn't think of what I could have done that would cause it to read so lean, so I took a screwdriver to it at the gas station to try to get it back in check. No response to the idle mixture screw, so I had either introduced a vacuum leak or... On the way back, once I got up on the throttle a bit it cleaned up nicely.
Back to the lab... I THINK what happened is that the gasket (a bit worse for wear after having been messed with so many times) was misaligned and was covering up the primary slow jet passage between the body and the air horn... Best guess, not sure. Once I got it back together though, I went for another run, and things were pretty damn close. It was dark, and BigCity's rig needed to be buttoned back up, so that was the last run. This time, things were looking REALLY good! Primary slow (hasn't changed since the beginning) was right in the 16-17 butter zone, primary main was just a skosh on the lean side in the high-17 - low-18 range, secondary slow was in the 14 range, secondary main was a buttery 13, and the power came in and kept it right at 13...
At that point, I pulled all of Ricardo's wideband kit off my rig, drove it back outside, and came in to help finish buttoning BigCity up and clean.
I'm going to have to wing the last bit by ear without further access to the wideband, but I'm close enough that I know where I need to be. I'm going to ream the 116 to a 117 and ream the 70 to a 75 (hopefully... those slow jets don't look easy to ream). While I'm at it, I'll mark the modified jets accordingly for future reference.
It's worth noting that this tuning was done in the cold. Cold air is more dense than warm air and tends to read a bit lean as a result. My mixture will richen up a bit in warmer weather, but I think that's acceptable (and I don't want to rejet seasonally since I'm not racing this truck or anything).
I had intended to follow a procedure that is much more precise and methodical from the start, but given that I was so close to start and the time constraints it didn't make much sense. If this proves effective (there is doubt out there), someone wants to volunteer their carb, and Ricardo cares to lend his wideband services again, we can go through the whole thing and document the crap out of it. I guess mine is going to be a proof of concept test in the meantime.
For the record it sounds MUCH better now, and at one point on the way home I looked at the speedo and was doing 80 without realizing it... It will also maintain 70 going up 25... The timing certainly helped a bit, but timing doesn't make an engine sound that crisp. I'm hoping to see fuel economy bump up closer to 15. With things cleaned up like they are, I have to use considerably less pedal, and when I do use the pedal I know it's burning less fuel. I'm going to get those last two jets dialed in over the next few days, then I'll fill the tank and have my first fully tuned baseline figure. Wish me luck!
