on a 90 f150 4.9 i have heard that it is non adjustable valve train you just have to torque the rocker bolts to specs is this true and if not do you have to preload the lifters? after replacing new ones.

 

Yes to non-adjustable valve train. Just torque them down. If you have replaced lifters, I'd suggest coating the faces with Comp Cams or CRC moly/zinc assembly lube or any other quality lube. Need to break in the new lifters while varying the RPM's between 2000-2500. I prefer to set all the lifters in some 30w oil overnight to expell any air that could be trapped in the plunger housing.

 

thanks and do you have to set valve lash?