OK, I have a Q-Jet, which should be hooked up properly (vacuum, etc.). I was trying to set the mixture and idle to run well, and ran into a bit of a hiccup. It now runs rough, and when cold seems to not want to run-it has also been cooler than normal here lately (not really for Chicago) it's been between 30 and 60 degrees out, mostly on the colder side for around two weeks now. So, to start with, if I really have no idea about where the settings were when i started messing with them, is there a simple way to get to a normal "baseline" so that I can adjust them properly? All I really know is that turning the mixture screws-they're the "jets" right?-to the right is supposed to make the jets lean, and turning them left, rich. Should I turn them all the way in-to the right-and start from there? Or am I better off tweaking them from where they are? I tried to make it lean, or on the lean side, since I would like some economy. If they are too lean, will it be tough to warm up, and idle rough (when cold)? It's almost as if it could idle forever and stay cold, so I give it a bit of gas, nursing it. Does the trick. If I am getting smoke from the tailpipe, can that be an indication of it being too rich? (I know it can be from other things). I am not sure the vacuum is set up properly, am still trying to find a Rivi shop manual that will not cost $100-good luck. Can someone please post the diagram, or pics from their shop manual from the 66 Rivi, so I can figure out the vacuum hookups to the carb, brakes, etc.? I had brakes checked and they said the vacuum was around 15, and needs to be at 20 for them to work properly. I know I have to go over the vacuum links, to make sure they are tight. I assume they could use help right now, since the engine is pretty strong, and runs pretty good, but like I said there was the brake vacuum issue. Actually, I had the pan from the tranny dropped, to see if it was sound or not, (it is, the fluid was clean, without much noticeable crap in it) and they checked the vacuum there, and it was around 16 lbs. Supposedly OK. I know this will sound dumb-are all the vacuum hookups related (other than being a function of the engine) I mean is it all in a loop, reciprocating? Like I said, I really could use the diagrams of the carb and vacuum, and brake link/hose setups! Thank you for any help! uzzled:
Well, I don't know much about tuning a Q-Jet, but I have worked on Holley/Demons a bit. For starters, I believe that the mix screws only control an idle circuit (at least on holleys), and then your jets which are inside the float bowls control the off-idle mixture. If the car blows a little smoke at WOT, I wouldn't worry too much as long as your plugs don't look too dark. If the car huffs black smoke while idling, the mixture screws are too rich...BUT... ALWAYS err on the side of rich, a lean condition can cause severe engine damage such as a hole in the piston if bad enough, and can make the car run hot also. Your fuel economy would be controlled mainly be what jets are in the carb, as well as where the secondaries come in. The later they come in the better fuel economy you get, but with less performance. If you are running lean, your car won't run as well cold. The best way to increase fuel economy may be through upgrading your ignition and making sure your timing and carb are adjusted correctly. Do you have a problem with your brake pedal being hard? You say that your car pulls 16lbs vacuum, this really should be enough for your brakes to operate. The grommet on the brake booster may be worn out, and this could cause the brakes to operate like there's not enough vacuum. Not all vacuum hook-ups are the same, some may be ported, and others not. I would believe that the brake vacuum should come straight off the manifold, so check that. Sorry I don't hav much more for you, but this is just what comes to mind. Let us know if this helps solve or get more definite questions for you.
Thank you Keith I will look to see if the booster is hooked straight to the manifold, and the condition the fittings are in. I think the shop I had it to (at) wasn't familiar enough with the older cars. I liked them though, they were nice and made sure I could see what they were doing, etc. They couldn't adjust the timing though-not a good sign. They said there wasn't enough vac for the brakes, and didn't have the specs for the dist., points, etc. Good to know about not wanting to run too lean, it may save me engine. Once again, thanks for the input.
