spottedog Posted September 20, 2017 Report Share Posted September 20, 2017 Have been working on1974 B210 with A14 in good shape, 550.00 spent for parts around March. Compression 120 to160 psi, no smoke but bad ignition parts (replaced), carb rebuilt with kit. Engine runs, new plugs, cables, points, coil, rotor, ect BUT :confused: engine rocks (hard) from side to side in the engine bay (new motor mounts were installed) dwell and timing are correct. Engine fires on all cylinders, but something is not right :confused: Quote Link to comment
wayno Posted September 20, 2017 Report Share Posted September 20, 2017 I don't know a lot about this subject, but I believe that 1 cylinder showing 120 next to another one showing 160, or even 160 on both sides of one showing 120 could make it rock at an idle, it likely would not be as dramatic at mid/higher rpms. I would check your valve adjustment. Quote Link to comment
Dguy210 Posted September 20, 2017 Report Share Posted September 20, 2017 Cold and low idle will also cause it to rock a bit, especially if running on old crappy fuel. How does it run when warmed up and above 800 RPM? Quote Link to comment
flatcat19 Posted September 20, 2017 Report Share Posted September 20, 2017 Mechanical timing? Chain off a tooth? Quote Link to comment
distributorguy Posted September 20, 2017 Report Share Posted September 20, 2017 What is your timing set at? Try 14 BTDC at idle (vac disconnected) and see if it smooths out. Check your vacuum advance function to verify it advances AND holds when you pull a vacuum on it. A leak can wreak havoc with idle quality. Make sure the vac hose fits tight and does not leak. Quote Link to comment
datzenmike Posted September 20, 2017 Report Share Posted September 20, 2017 Uneven compression will do this. Ideally you want all readings within 10% of the rest. For 160 the rest should be above 144 or if 120, they should not be above 132. As you can see that one very low cylinder's not doing it's share of work at idle. Have you checked your valve clearances on that cylinder? A tight valve will not seal as well. Squirt a couple of teaspoonfuls of engine oil in that cylinder and retest. If the compression jumps up then most likely the rings are not sealing in the compression. If no significant change in compression, then a valve is at fault. Quote Link to comment
distributorguy Posted September 20, 2017 Report Share Posted September 20, 2017 The compression numbers may be screwed up with more fuel in the low cylinders unseating the rings. Bad carb or ignition can cause this. If the low plugs are wet, then the compression will likely come back with a tune-up and some miles. Rusted valves and seats that sat open while parked for a long time will do the same - for example if it hasn't been driven since March? Too little info for any of us to provide any more than a guess. Basic tune-up: adjust valves, sort out ignition, sort fuel delivery - in that order. Your plug wires should be less than 5000 Ohms each. Don't overlook this bit of info, even if they're new! Quote Link to comment
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