What type timing sets did you use, one that you can only install one way or has key-ways for advancing or retarding cam? Did you use a degree wheel and properly locate TDC 1 st?

Could be a broken intake rocker, loose rocker not seated, leaving the intake valve closed

Compression test would show it immediately, especially on a new build. Don't run it until you figure it out

That's what I was wondering too-is cam timing correct? If NOT you will see a small acrossed the board difference in compression, who assembled the motors? I recently fixed a Oldsmobile that's cam timing was whacked off in left field built by a supposed engine builder, the engine builders response to me finding the cam timing off was IT CAN'T BE OFF- I LINED THE MARKS UP!!!!!

question for the op,why did you go with a cam with a non traditional firing order.

first off thanks to everyone for the input...

The top ends were spec'd by Bob M. Retro hydraulic rollers in Gen V blocks. Used his custom grinds from Cam motion, Morrell lifters, Isky 9005 springs, Manton pushrods, and Rollmaster adjustable timing sets. 088 heads with some pretty extensive head work. I had the heads flowed prior to spec'ing the cams and they were good to .700 The cams have 4* of advance ground into them and the bottom ends were built and cams installed by a very reputable local builder that I have worked with on several other projects. Cams installed at 0* due to the ground in advance and the builder said they were spot on. The bottom ends are Callies/Oliver/JE. The firing change order was done by Bob. The reason I tore these back down after about an hour was because of this issue. First thoughts were a vacuum leak but we could find nothing. When I reassembled the top ends I swaped the heads from the other engine and the issue stayed the same. I am thinking either bad distributor (timing) or wrong cam grind as the other engine runs great. Thanks again to everyone! keep the input coming.

im hoping bob will chime in on my cam question as im very interested in learning why he specked these cams.

have you spoken with bob about this,if anyone can help figure out what is wrong it,s him.

can i ask who the builder is?

I never chime in on any of these types of threads but am very curious as to what is causing the issue. You said a builder installed the cams and everything was on. With an off the shelf cam this seems to be standard procedure. My question is that since you have a cam with the firing order changed is it necessary to check every lobe to verify that it was ground accurately? Don't mean to hijack but curiosity got the better of me, hopefully some of the other guys will clarify. Good luck, they should push your .38 special very nicely!