318 cam

65Dart270Sedan said
What is the biggest cam you can put in a LA 318? I saw something about you can’t put high lift cams in them without grinding down the valve stem guides. Also, what mods other than springs will need to be done?

What exactly do you mean by "how big a cam?" You can put a long duration cam in, but you will loose bottom end torque and gain high RPM power. For that the rest needs to be up to the forces the RPM generate. Rod bolts and valve springs come to mind just off the top. A high lift lobe also accelerates the valvetrain to higher velocities, requireing stiffer springs. The other issue is retainer to valve seal clearance and then coil bind. If measuring the retainer to seal shows that the new lift will cause interference, the guide needs to be machined as Rusty states.
An engine is a compendium of compromises, and the weakest link will fail. Putting a "big" cam in an engine with factory shortblock and valves is a disaster waiting for the time and place to happen.
There is a fellow races a 1941 International at Bonneville with a 16V92 on the frame behind the cab. His tow vehicle is a '70's vintage Chev 3/4 ton truck. Well it appears to be that. Has a 5 ton frame, 6V92 with twin turbos mounted on the manifolds to fit under the hood, and 8 spd transmission (Fuller I think) and SQHD axles. You would not want to install either engine with a stock frame as you would probably make a pretzel out of them. The old weakest link story.