i bought a 1995 600 F3 with a blown engine, somebody blew a rod and messed a lot up. i bought a second engine that we will call engine 2. we took the bad parts out of engine one and replaced them with the good parts of engine 2. So what we ended up with was a lower case/ transmission from engine 1, upper case and cylinders from engine 2. head from engine 2, and pistons from engine 2. We did everything we were supposed to when taking an engine apart, like new rings, gaskets, and I lapped the valves because i couldnt find anyone to do a valve job. i now have an engine that will turn over, it gets gas, and it gets spark, but it only has 50 pounds of compression across every cylinder. that is the problem that we believe is preventing it from starting. we checked and double checked the timing, which is now correct. and we did a squish test and we have about 1.4 mm of squish instead of the .7 that we were told is normal. One idea is to deck the cylinders, but i want more opinions from people. please, any help? i need it desperately. Any tips or ideas, even if they seem obvious to you they might not be obvious to me.

Also, sorry for the very long post. i just needed to give background on what i did.

 

Cam timing off, valves too tight, valves not seating, or cylinders are tapered. That's my guess... Hopefully you got the rings in the right order, oriented correctly, and the ends of the rings are staggered (not lined up)

 

Might be a stupid question...

But if you bought engine 2. Why didnt you just use engine 2? Why swap parts?

The reason I ask is... was there a problem with engine 2 as well? Maybe something that you didnt notice is effecting engine 3(1+2)