Hey all, after dealing with A/C, fan, and cooling fan problems, I’m back up and attempting to drive again. I had a few topics before about my car stumbling when it shifts and whatnot, but I decided to start again and mess with everything just to go through the checklist again.
The biggest issue I’ve had, is that when the car shifts up, most noticeably from 1st to 2nd, under light to medium throttle, it stumbles. It’ll stumble until I give it some time, or if I try to power through the stumble, sometimes it’ll pop, and afterward it’ll get to normal much quicker. Overall, 2nd gear is fairly unresponsive to throttle, especially around 20-30mph.
I’ve got a 351C, 2V, with a Quickfuel 680 4 barrel, Edelbrock Airgap intake, custom cam with .610 intake, and .617 exhaust, 225/233, 113 LSA. The heads were cut a bit to get a smaller chamber size, and the cam and pistons were made by Brent Lykins; he also recommended the carb. I swapped out my FMX for an AOD, that also has a shift kit.
I’ve messed with the carb, I thought the pop from the carb was from being too lean and so I swapped the jets from 70’s and 74’s to 72’s and 76’s, but it didn’t do anything. I swapped back, and then checked the plugs and found that they seemed like it was running quite rich, less than 100 miles and the plugs were black. I fiddled around with it a lot, and now I’ve ended up with 66’s and 70’s, which may still be too rich for it since the exhaust smells fairly rich. I’ve got the fuel level set at barely the bottom of the sightglass, and I went with advice from holley on how to tune the idle mixture screws, I had it turned out a bit and slowly turned it in until the vacuum level and rpm deteriorated, then went a little bit back.
I’ve been everywhere with the distributor, MSD Ready to Run unit, #8350. I’ve used the heavy springs, light springs, blue, black, and now silver bushings. I’ve had the vacuum on full manifold, and ported, and now I’ve got the vacuum advance disconnected completely. The current setup I’ve got is the silver bushing (25 degrees) with heavy silver springs, initial timing is ~10-11 degrees. Before this I had the black bushing, with a ported vacuum line on the vacuum advance, and I noticed what I thought was pinging sometimes when I would shift, so I went to the heavy springs to slow the mechanical advance, thinking that they’d be too slow but they seemed fine, however I’ll probably swap the springs since those heavy springs put the silver bushing all in at just shy of 5000 rpm, quite a bit later than I think is needed.
I considered fuel starvation, however if I just floor it, and let 1st go as long as it wants, and then it shifts, it has no stumble or problems that I’ve noticed, and I can keep goin with around 6 psi the whole time. I’ve swapped multiple spark plugs in and out of it, all have come back with black soot on them, I haven’t checked these recent ones but they were run with a richer setup before so I’m sure they’re black too.
The only other thing I’ve thought of is the transmission, since it’s occurring during shifts and immediately after. I’ve only got the stock torque converter in there, and that shift kit worries me. I think the shop that did the rebuild is fine, I just wasn’t looking for a shift kit but theirs was the closest available rebuilt AOD. I would think that if it was the torque converter that there would be problems at light throttle and at WOT, but only at light throttle makes me think its just a tuning issue, however torque converters are not something I’m too familiar with. I’ve had the transmission line pressure checked and set, and it did fix a problem I had previously with shifting into 3rd, however it didn’t seem to affect this problem at all.
Any ideas or help would be appreciated, I’ve just run out of ideas since nothing I’ve done has had any major change, and since everytime I try to test things out, once the car warms up a good but the problem gets slightly better, and so I can’t tell if what I’ve done has had a positive change or not. I’ll see in the morning if the mechanical only timing will fix anything, but I am doubtful. Thanks for any help.