I have a Mazda Magnum Pick-up with a Ford 3.4 l V6 engine in it. The Engine started making noises and running badly. Compression test showed 0 psi on Cyl 5. I have now stripped the motor. The exhaust valve on No 5 cylinder is burnt oval. The exhaust valve on Cyl No 1 is just starting to burn. The 1st cam lobe on the camshaft has great big chunks of metal broken out of it. The oil pump is badly damaged. Basically the motor needs a total rebuild. Apparently this motor had hydraulic valvelifters, someone has changed them to solid lifters and changed the rockers to adjustable type.All the lifters are showing signs of pitting and need replacing.

Can anyone tell me why someone would change the lifters from hydraulic to solid and should I change it back to standard hydraulic lifters or keep it with solid lifters when I rebuild this motor. The engine code is B13D

Any advice will be appreciated

Thanks
Alan