Hey, I am having a tune-up problem with recently parted together Model A pickup with Mopar 360 and Holley carb. While driving with constant speed, constant revs, speed 40 or 50 or 60 mph, then engine misses. It is clearly felt that sometimes it does not fire correctly, about after every 4 second or so. As it doesn't ever miss at idle, nor during acceleration (both WOT and medium throttle acceleration), then I don't think it is ignition related. I tried raising the fuel level in carb, but no change. Right now the fuel level is in the lower edge of sight hole, as should be. Could it be rich, lean, wrong jets or something else?
Could it be rich, lean, wrong jets or something else? The plugs should tell you, A wide band o2 will Tell you also. Under The circumstances when the problem happens that you describe, the manifold vacuum will the at its highest. Check that vacuum level with a test drive and vac gauge hooked up. When you say it doesn't happen, vac levels are lowest. You might have a latent and tricky to find vac leak at those high levels, you could have an advance unit that's worn or touchy.
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