I have a 74 390, it runs fair with RV cam. I have never seen any blue smoke out the exhaust and the plugs are clean. I am not sure what has been done to the engine as far as total rebuild, the pistons are 30 over. My compression test when hot, all the plugs out, and wide open throttle ranges with one cylinder 95, two at 105, and five at 110. Adding some oil to each cylinder test got me one cylinder 1% increase, four cylinders 4% increase, two cylinders 7% increase, and one cylinder 8% increase. What does this mean?

 

a fair running engine

 

Do you have any blow by? 10% is the max diff. on compression readings and ideal is less than 5%.

 

No blow by. All my plugs are clean except for number one, its not fouled and its not wet with either oil or fuel. The other seven plugs look like new with 2k miles on them.

 

Those compression readings just means it has a few miles on it, nothing drastic at all. I had similar readings on my 352 at one time and drove it for five more years with no problem.

 

It has a slight miss on occasion around 1500 rpm almost like its not getting enough fuel, espically if you are going slow and the transmission stays in third without down shifting. If you get on it there is no miss. I almost think i have a carb issue and it has been this way since the carb was new. I am going to increase the pump nozzle shooter size and see what happens. I have done this one time before and it seemed to make a small difference. I just watched a video on how to perform a leak down test i may do this after the pump nozzle change.

 

Started back tracking my upgrade to find what has caused my problem. Timing gears were lined up correctly. Took the heads off and all but two exhaust valves were up in the head past the flush point. Dropping them off tommorrow to get reworked.
Down in the cylinders on the cylinder walls i see a tint of copper within the hone marks, is this normal or a wear sign?