Re: My Latest Carburetor (q-jet guys will get a kck out of t
Soooooooo, the jeep has been busting my balls for a while now, I'd get it tuned in all nice, nice in the garage, take it out for a drive, idle would go sky high, and then I'd make an adjustment to bring it back down, go for a drive, sky high again.
I'd it get to idle down, and it would end up with a hard start, extended crank, poor idle, or dieseling upon shut down. I finally got it to a point where it would start OK, run good, shut down OK, idle pretty smooth (bout how it did with efi), but still too high, nothing I did seemed to make the thing just work smooth, that was, until Saturday.....
When I built this Carb I didn't realize there was such an animal that existed, a Q-jet with no timed vacuum port. I didn't find this out until I had it all put together and running, went to hook up the vac advance, and found only full manifold vacuum on the carb. I figured, eh no big deal, I did some reading about using full manifold vacuum, found that many folks favor it over timed vac, so I decided I'll give it a shot and see what happens. As you read above, I have been fighting with getting it tuned in right. Everythng from crappy idle, to miserable cold weather starts, to extended crank times on warm starts. Friday night got very pissed off at the thing as I pulled into my driveway and the idle shot upto about 1200. Started look around at my parts carbs, noticed there were a few that lacked a timed vacuum port, but I did find one, that had what I wanted, and was a good enough unit to use.
I spent Saturday afternoon, into the evening tearing the base plate down, cleaning it, tweaking it to work properly, in prep for installation on my carb. This is only change I made, just the base plate with a timed vac port, I installed the idle mixtures screws as they were in the non timed plate, I made no adjustmenst anywhere else. I bolted the carb on, and fired it up, adjusted the idle, let it warm up good, got the vac gauge out, set the idle mixture screws, and that that engine has never run smoother or quieter, I was more than pleased to say the least. I hopped in and went out for a test drive, came back, had to knock the idle back down a tick, shut it down for the night. Went out sunday morning, (cold btw, maybe 20 out), gave the pedal two pumps, it fired quicker than ever, did not try to stall (another thing it was doing), made my adjustments to my high idle, and it worked exactly how I wanted it to. Now when I pull upto a stop light, in drive, the jeep idles at about 500rpm, smooth as could be. The ill effect of this minor change, damn secondaries are out of whack again, :lol: . Before I proceed with that though, I figured it may be in my best interest to find out what the factory timing curve looks like on one of these engines, being impatient as always, I didn't think to check it when it had efi, lol.
At any rate, jeep is running very well now, and finally, I can honestly say I'm happy with it. What baffles me, why the hell would it be untunable with full manifold vacuum, what are the people doing different to be able to use it? Personally I've always used timed, but I often hear others praise full manifold as superior to timed? I don't consider myself great with tuning, but I'm not terrible either, this thing was making me look like a monkey ******* a football, hahaha.
. The jeep is still 4wd though, interior is all disinfected, cleaned and installed now :lol: (minus a carpet).
