1968 Coupe 289 with Hollybrock performer carb and manifold. I'm totally baffled as to why the engine is missing when ticking over on the last two cylinders on the left side at the back. When i take off ht lead of either of the last two cylinders it makes no difference, although there is a good spark shooting across to the plug, when you rev up it seems to clear. My last resort is to remove the heads thinking that it could be burnt vale or sticking valves, compression on the cylinders are between 130-140. I have checked the timing, points, distributor cap, coil, all the obvious things, with no success. I would be glad of any ideas.
1968 Coupe missing on two cylinders
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BullittStangV8
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When I bent my valves I had a similar experience, although my compression on those two cylinders was far far less then those of the the good cylinders.
misfire
If you're car is misfiring at low or idle speeds, the 1974 Motor Auto Repair Manual sais it can be the following:
1.Faulty plugs( you said you checked those)
2.Plug gap too narrow.
3.Spark Plug wires( aka secondary ignition circuit)
4.Bad distributor cap
5.Dirty Air cleaner
6.Leaking valves
7.point gap too narrow( if it still has points)
8.Faulty carburetion
9.Air leaks in intake manifold or carburetor
10.Leaks at fuel pump check valves.
11.Air leak at intake valve stem.
Basically, you said that you had checked the electrical system. I would check for vacuum leaks at the carb and intake manifold gaskets first since that is straight forward.
If you're car is misfiring at low or idle speeds, the 1974 Motor Auto Repair Manual sais it can be the following:
1.Faulty plugs( you said you checked those)
2.Plug gap too narrow.
3.Spark Plug wires( aka secondary ignition circuit)
4.Bad distributor cap
5.Dirty Air cleaner
6.Leaking valves
7.point gap too narrow( if it still has points)
8.Faulty carburetion
9.Air leaks in intake manifold or carburetor
10.Leaks at fuel pump check valves.
11.Air leak at intake valve stem.
Basically, you said that you had checked the electrical system. I would check for vacuum leaks at the carb and intake manifold gaskets first since that is straight forward.
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