Hey guys, I am need some different oppinions here. I have a 406 that I am having trouble with. It sounds like it has a miss. I have ran compression test and all cylinders but number 1 had 175 compression. At first number 1 had none, "the motor was built than sat for a few months". So we did a leak down and the exhaust valve had 40% leak down. I tapped it and it built up and now all cylinders have 2% or less leak down. The motor runs better but it still sounds like its backfiring through the intake? I have readjusted the valves, checked plugs, look for burnt wires, checked timing, retorques the intake manifold. I'm stumped. Also the car only has 5 inches of vacuum and fluctuates rapidly and comp says it should have around 12 inches. Here is the specs.

406
comp xe288 cam 236/242 at .050 hydraulic
holley 750 double pumper
Msd pro billet distributor
streetfire wires
harland sharp 1.6 rockers
dart iron eagle 215 heads had ported/valve job
motor should be 10.4:1
700r4 with 3000 bdr converter

any suggestions would be appreciated. The motor just runs awful when under aload, but in idle or just reving it sounds fine.

 

What was your valve to piston clearance?

 

Ran into that once
Wires on cyl 2 and 4 were reversed. Coulda fooled me!

 

Well, I checked all the wires and all were good except number six. Started it up and same thing. So took the intake off and checked it. It was warped pretty good. Took the coating off and tried it and same thing . We set the valve to zero and started it, run perfect steady 12 inches. So, I guess the second set of lifters from comp are no good.