found lean best idle at 1 1/2 on the mixture screw. 1 turn in on the speed screw only gives me 520 rpm with 3 inches of vacuum. what am i doing wrong? the speed screw is in too far is what i am feeling but i don't know how to increase my rpm without adjusting the speed screw. any adjustment on my timing makes it want to shut off.
things are looking up. finally idles and no dieseling when shut off. idles right around 620-ish rpm +/- 200 rpm fluctuation. timing at 12*, but fluctuating b/w 14-11*. mixture screws at 1 turn out. speed screw in about 1/8 turn. found a vacuum leak under the linkage plate i bolted into the intake. fixing that ASAP. still no s port hooked to dizz and not sure how to tackle the 0 vacuum at s port at idle issue. would love some more help. thanks to everyone for helping me get to where i am now. haven't driven it yet but keeping fingers crossed that i will be pleasantly surprised.
This was your post #460.
It looks like things have changed.
seems so. i removed a bracket that was bolted into my manifold to eliminate a vacuum leak. i then drove it around and realized it had a huge amount of pre-det. retarded the timing to eliminate the ping and here i am now.
things are getting better if i ignore the blatant that slaps my face and focus on the big picture. i have a better jetted carb, i'm sure, and have also acquired a new timing light and vacuum gauge. can't gripe about that. have any suggestions for me? could it be my minimal vacuum line hook-up?
i have not checked manifold vacuum yet, only ported. i have not removed the FPR but i did re-route so the filter is closer to the carb, away from the exhaust manifold, and oriented in the 12' position. will it help if give you a reading of manifold vacuum at idle?
This is what a manifold vac reading will tell you:
"When using the gauge, hook into a good port directly off of the intake manifold. Any competent engine should be running between 18-22 inches of mercury.
(1) The vacuum gauge can be used to check for a leak in the valve train, intake manifold or head gasket. With the engine at normal idle and at operating temperature, hook up the gauge. Normal operation would have the needle/ pointer holding steady and not fluctuating. If the needle holds steady, than drops an inch or more, and then returns again to normal, and repeats… this signals one or more engine valves are closing but not seating properly, thus creating a leak. Each time the valve doesn't seat properly, the pointer fluctuates. The fluctuation isn't much, maybe 1-3 inches of mercury.
(2) If the pointer drops sharply 5-10 inches from normal, and then returns… this signals a cylinder head gasket. This behavior will repeat itself. If the leak is between two adjacent cylinders, the leak will be more pronounced.
(3) If the pointer/ needle fluctuates constantly at a reading of 3-8 inches of mercury BELOW normal, It indicates intake system leakage.
(4) If you think you may have a "back pressure" issue, get the vehicle at normal operating temperature and slowly bring engine to 2,000 rpms. Close throttle quickly. If no back pressure is present, the pointer will jump past your normal reading and smoothly return to normal, just as fast. If it is slow or uneven return, there is an issue of back pressure. You can also test it another way… hold the engine at 2,000 rpms and watch needle. If it begins to decrease gradually instead of holding steady, there is an exhaust restriction somewhere.
(5) Continuous pointer movement an inch of so above or below normal indicates the need for further checking of the ignition system with electrical test equipment. You may have a weak ignition coil, high tension cable leaks, bad distributor cap, bad spark plug or incorrect spark plug gapping.
From "Petersen's Basic Tune up and Test Equipment."
manifold vacuum readings... when i increase rpm with speed screw to 820, vacuum reads 16.5, and fluctuates to 16.75 and back. idle rpm jumps between 790-840, but most constant around 820. for some reason in the beginning of the test my timing gun would read 710 in a flash, and then read back to 820ish. when my electric fan kicks on the idle and vacuum drop. does that tell us that i need to test some electrical components?