My 1970 V8 has had an intermittent misfiring problem which is making the car undriveable. If I go for a drive, within seconds it will misfire. If I rerun home, and allow it to idle of a couple of minutes it clears and revs from idle very smoothly until I take it down the road again. When the misfire occurs, it is affecting cylinder 4 and 6. The usual hot and cold compression test has been done, mixture check, ignition checks done etc. The engine has recently had a top end rebuilt and was running a treat until yesterday. I decided to remove the carb that feeds the even numbered cylinders this morning to check that all was well. I peered down the hole in the inlet tower and saw a small pool of blue coolant in the bottom. The throttle butterfly on the carb also seems to have a few tiny coolant drops on it. Does this mean that there's an internal coolant leak on the manifold, causing my misfire? If so, is the manifold scrap? (I have a spare one). It's the original manifold with an 11/9/69 stamp on it.