Hi! I just joined the forum in search of some possible solutions.
I just finished rebuilding a chevy 250 engine in a 1966 Biscayne.
It had only 70,000 miles on it and I had to rebuild it with engine in car. It had one piston burned all the way down the side. Not much ridge in the cylinders. I replaced all the pistons rings and rods bearings, put a new head on it as old one was shot. I got it running ok but its running kinda rough. I have adjusted the valves 5 times. I turns out it will only run reasonably well with the valves set at right at about zero lash. It has hydraulic lifters and I took them all out and cleaned them and put them back in put new spring clips in them instead of the ones that it had as some of them were broke or near failure. If I adjust the vales according to manual where you give them a full turn after zero lash the engine runs really rough and shakes all over and two or three of the cylinders act like they are missing. I pull the plug wires to see which ones make a difference when running. So I suspect some valves are not closing all the way when I have a full turn on the lifter adjustment. At zero it runs pretty good but still a little rough. I tried half a turn also. So what is happening are the lifters pumping up too hard? air trapped or what. I put a high volume oil pump in it also. I would like it to run real smooth, but have not been able to get it to do that yet. I did put all the lifters back in the hole they came from. got two mixed up and bought two new ones to put in that hole. They all seem to be lifting fine, the cam was in OK shape. Got plenty of oil coming up through all the pushrods.
