[padadmin]

I have a 66 289 with 12,000 miles on it. It continually misses on the drivers side back cylinder when it is cold. Once it reaches optimum temp it runs perfect. Changed points, cap, rotor, plugs and wires. Still the same cylinder misses. Have a newer Edelbrock intake and holley 4 bbl. Compressions is good in all cylinders. Any ideas?

thanks

[woodz428]

It could be a number of things, I would first check for a vacuum leak on that cylinder. I like to use contact cleaner ( a flammable type) because it evaporates quickly and doesn't leave a mess, when cold an engine needs a little richer mixture and if that one is drawing just a little air it could miss until it warms up. I said it on another post , but check the valve setting on that cylinder, I had a 351C that had one tight valve and would drop it when it was cold and the oil was thick, it would also do it when warm when the engine was wound out and pumped the lifter up, after it set idling a few minutes it would pick back up. On that engine ( at that time) you had to get shorter pushrods, now they make shims, hopefully yours aren't postive stop and can be adjusted otherwise the only way to check is to collapse the lifter and check clearnce between the rocker and valve.

[padadmin]

Did check with cleaner and didn't do anything. I was hoping that was the problem. This weekend will pull of valve cover and check valves. Now I am hoping that is it. I didn't build the engine so am searching without knowing all that had been done to it. Will let you know. Thanks for the advice.

[padadmin]

Well this weekend did a compression test on the cylinders. 120 on all but the one not firing when cold. (Is 120 good?) That one showed 80 and then 40. So I loosened the tappets and did another test and still 40. Put oil in cylinder checking if rings. It stayed at 40. So figure valves are bad somehow. Readjusted the valves and off we go. Since that day it hasn't missed and has ran the best is has since I have owned it. So going to drive the beast and hope for the best. Will start looking for another motor to rebuild in the meanwhile.