I have rebuilt and assembled my qudrajet using Cliff Ruggles book. It has helped the car idle better, but not like I think it should. I can idle down the engine to 700 rpm but at that low of a idle the car surges and fluctuate the rpm. I can screw in the adjustment screws and get a reaction and when I screw them out I get a reaction also. I can place my hand over the carburetor while idling and the engine will speed up and smooth out. I have checked for vacuum leaks (ok), taken a compression check (ok), all plugs are firing (tested). Timing is 30 @ 1500 rpm as recommended by John Osborne. Vacuum is around 13 to 15 at idle. I soaked the carb body in car cleaner and checked all of the passages to be sure they were open. Any Suggestions to what is happening and what I need to do. Also how much play should be between the top of the accellerator pump rod and the lever which pushes it down? I have almost 3/8" Carb number is 7043240 Primary Jets are 75 Primary Metering Rods are 45B Lunati Cam 33304 230/240 455 Engine 1970 Stage One Heads (iron)
If you place your hand over the carb, the engine should die out as your suffocating it. If the idle picks up and smooths out, you have a vacuum leak. Try carefully spraying Gumout around the carb and see if the rpm picks up. Most of the time the leak is at the airhorn gasket. Ive had to double up the gaskets to get them to seal
It will die if I completely cover the opening. I have sprayed around the base, air horn, primary shaft and do not see any changes.
Try misting it into the primaries and see if the idle goes up. It could have an internal vacuum leak. From here, it sounds like your carb is running super lean.
With 230/240 degrees of duration with the cam, it is pretty amazing you can idle it down to 700 rpm at all. What happens when if you idle it at 900 to 1000 rpm? The idle characteristics may be normal with such as big cam at 700 rpm. Thanks, Ken
Try installing stiffer distributor springs. Having all the timing in at 1500 rpmis very early, I would think there may be some timing flucuations at idle. Also check your Carburtetor power piston spring, it could be opening and closing at idle causing a surging idle rpm, if the spring is too strong.
I drilled the idle tubes to .038 and the down channel restrictions to .052 (or there abouts, can't remember exactly). That helped my idle a lot. I think there are different length accellerator rods. The lever should be touching the rod. You may have the wrong rod. Like greg said, check your metering rod spring. It may be too stiff. 230 on the intake lobe should make just a slight lope. You can put a pencil down the vent tube and watch it to see if the spring is lifting the metering rods at an idle. Your metering rods look a little thick to me.
A couple of things come to mind with this set-up. As mentioned earlier, check the timing, as fluctuating timing can affect the idle. Also, you did mention whether the 700 rpm was in gear or park. 700 in gear might be a little low due to the cam, but you also mentioned that the compression was good, but did not mention what it was. These engines were low on compression from the factory due to emissions regulations, and more cam could easily aggravate a situation. Pls tell us more. Ray
Also adjust the idle mixture screws to get the highest vacuum readings with the car in gear (wheels blocked and e-brake on) and vacuum advance disconnected and plugged.
Something to check is whether both sides of the carb are feeding fuel at idle. Qjets are notorious for the idle circuits to feed on only one side. Sprits carb cleaner into one sied, then the other, noting whether one side responds better. This will be a clue. You clould also check for whether the cylinders missing have a pattern, such as 1467 or 2358. If so, the carb circuits are likely the culprit. Let us know... Ray
"Try installing stiffer distributor springs. Having all the timing in at 1500 rpmis very early, I would think there may be some timing flucuations at idle." +1 Verify with a timing light that no timing is being added at idle speed. There is no need for such a quick spark curve. If the timing is all in by 2800-3000rpm's it will be soon enough. I run stock weights, springs and center cam in my HEI and my 455 pushes my car nearly into the 10's in full street trim. I've tossed out more aftermarket light springs, and weight kits than I can count, and replaced them with stock components. ALWAYS a positive result, and idle quality is greatly improved, especially when the trans is placed in gear. IF your engine requires tons of timing at idle, either increase idle fuel delivery, or bring in some timing via a vacuum advance unit with manifold vacuum. I don't like the second scenario unless the first one doesn't make it. .052" idle down channels are not enough for the 230 @ .050" cam, open them up to .055 to .059 and see if it helps. If it improves, you might try re-sizing he large lower idle airbleeds, and leave the upper ones alone. This usually does wonders for the early Buick carburetors.:beer .....Cliff
