OK, I give up. I completed my engine pull, new rear main seal, 4 bbl Qjet & intake manifold swap, and reinstall. She runs pretty good at idle, but I need some help getting the final carb tuning right. Can anyone recommend a good carb tuner near the Milford/Novi/Brighton area? Thanks. John
you're in the neighborhood of the Jensen's of Pure Stock Drag Racing fame. I think they could refer you to someone or maybe help you out themselves. If you go to the forum about racing in that series and the F.A.S.T. series I'll bet you get a quick and first rate referral.
Thanks, guys. I talked with a friend at work and now I want to try a few more things before I call in the cavalry. One problem I have is that I can turn the idle air mixture screws all the way in w/o having any appreciable effect on vacuum (only about 17 in Hg) or idle rpm. Another is that sometimes (only sometimes, not always) when I shut it down, I get fuel seepage from primary throttle shaft down side of carb. About a tablespoon. I had two throttle plates when I rebuilt the carb and chose the one with the tighter shaft-to-body fit. Both issues seem to indicate an overly rich mixture. I checked/rechecked float level at 15/32" and it doesn't seem to be hanging up. I had the timing out of whack and cranked in more advance and she idled much better and finally pulled 20 in Hg vacuum. Timing light indicated over 12 degrees advance, so I figured that the distributor was off a tooth. I restabbed it, then my timing light (1972 Montgomery Ward - I have the receipt) quit. I bought a new one and haven't had a chance to get back to it yet. My plan is to set the timing a 4 degrees btdc with vacuum advance to distributor plugged, check dwell, and try tuning again with idle air mixture screws at 2 turns out. Basically, start over with a confirmed ignition setting. Ideas are welcome. John
Qjets are notorious for idle issues. They typically result from plugged passages, and the result is that the cylinders fed by that passage will not run, or run poorly. The idea is to first determine which cylinders are not running, by pulling plug wires. Carb issues are typically indicated if the pattern resembles 1,4,6,7 or 2,3,5,8 not running. This is due to the set up of the intake. I would start there. Ray
The distributor is not off a tooth. I see that thrown around a lot, and it makes me wince. If you can adjust the timing to what you want without running out of distributor rotation, it is not off a tooth. Fact is, your Buick engine will run much better at 12* initial than it will at 4*. If you want the engine to run it's best, you will set the total timing, not the initial timing. The only instance your engine runs at the initial setting is when it is stopped and idling. Once you accelerate, the engine runs above that initial timing due to added mechanical and vacuum advance. If you are looking at the stock specifications for your year engine, they only apply if you have the same distributor in the engine that it came with. How likely is that on a 30+ year old car. Even if the distributor is original, there is plenty of room for improvement. A common problem with Q-jets fitted to modified engines is nozzle drip. If the primary throttle blades are too far open, the engine will begin to run on the primaries, and fuel will feed from the primary nozzles at idle. The idle mixture needles have no effect because you aren't idling on the idle system. You are already on the primaries. The engine runs rich and the exhaust is irritating. More initial timing allows you to close the throttle blades by backing off the idle speed adjustment. This will give the mixture screws back their function. I'm not saying this is definitely your problem, but it could be. Different distributors from different engines and years have different amounts of mechanical advance built in. That is why you need to set your total advance, not the initial advance. Once you set the total advance, the initial is what it is. As long as it is not too high, and you have no starting problems, you are good to go. The engine will love 12* or more initial as long as you don't over advance at higher engine speeds. Read my Power Timing Thread for more info. http://www.v8buick.com/showthread.php?t=63475
Larry & Ray, Thanks for the advice. I finally got back to the car after working through a lawnmower problem. Looks like I have the dreaded primary throttle shaft vacuum leak. Spraying carb cleaner on the outside of carb noticeably changes idle speed. Until that's fixed, I'm not gonna get anywhere with tuning. I think (?) that is why tuning my idle air screws has so little effect. Emailed Cliff Ruggles about a rebuild, but he has work backed up (I guess that's what happens when you're good). Thinking about rebushing it myself or maybe just starting over with a National Carburetors "new" rebuilt unit. If I fix the throttle bushing, I'm not sure whether that would fix all the issues, as this was my first carb rebuild. They say that you learn by making mistakes, but if that's true, why aren't I smarter than I am? John
You might check with Cliff regarding a possible replacement unit. I would trust his "replacements" before I trusted others. Not saying that there are dishonest people out there, just less than fully informed. From what I see, Cliff is the most fully informed, to my knowledge. Too many replacement carbs will fit too many applications, with too few of them just right. Just a thought... Ray
