Well after doing a compression check. I am running 155-160 on 1 2 3 and less than 20 on 4.   We believe it is a burnt valve,  no smoke from exuast.  How can i be sure without removing head?  I have been wheeling this vehicle for years and Havent really noticed any power change, just happend to check pressures and found this. 
    My zuk is a 1990 EFI, will the head interchange with a carb head?  Other than no mechanical fuel pump, can I just block off the fuel pump hole? Also, any recommendations on where to buy a rebuilt head?  I would like to go with a different cam and maybe a header install.  Any suggestions before i go through the hassle of removing the head?

less than 20 on a cylinder and you dont notice?

guess it must have always been that way , cause i lost 50% in 1 cylinder and it was quite obvious.

thats all i got to offer,  sorry

i sold the motor and bought a newer one.

88  to   a  92

I have been running this samurai for 10 years now and never adjusted the valve lash.  The exaust valve on the "4" piston was not closing all the way.  I had to turn out the ajusting screw about 2 full turns before i had a gap.  Checked pressure after adjustment, and got 140..  Started it up and ran some water through.  Ran around the yard, was even able to do some power slides in the driveway

Adjustment of valves is a good thing! My brother had a Nissan 720 pick-up for 8 years, and he put over a half million miles on the original motor, without a tear down. He swears that the secret is to adjust the valves.