so i bought a poss with bent valves an 89 rex to be exact i got a free y7 head and put it all together

so d15b2 with y7 head

number 3 cylinder is missing ive checked plug wires and cap and rotor even swapped the distributor its dual point so it cant be the fuel supply and it seems to have spark at the plug ive changed the plug too it has 90 psi of compression on that cylinder which is weak but i would think it would fire .... any ideas ???

 

What was the compression like in the other cylinders? I think checking for routes in which the pressure could escape through would be the first thing to do. Im assuming that the cylinder is missing due to the lack of compression. So find the reason why your cylinder cant hold the pressure and it may solve your other problem.