I have a 350 tpi engine bored over to a 355 just.

Unless you have something I'm not familiar with, you're tightening down what is supposed to be the valve adjustment. There's no torque value for the rocker arm nuts, just a setting, meaning position, not tightness.

No. It's a critical adjustment. There's two ways to set the valves. One involves a chart that tells you to place piston # 1 at top dead center, then adjust specific intake and exhaust valves until there's no free play when you wiggle those rocker arms, then go another specified amount, usually 3/4 turn, as I recall. Then you turn the crankshaft 1/2 revolution and do the next valves in the sequence.

The method I prefer is a little messy but I find it's more accurate. Fashion some shields out of cardboard so the splashing oil will run back into the heads. Loosen all of the rocker arms enough to have free play, snug them down just so that free play is gone, then start the engine. You can expect to hear some clattering if this is the first adjustment. Loosen the first nut until you hear that rocker arm clatter. Snug the nut until the noise stops and remember that spot. Snug the nut another 1/4 turn. The engine will misfire for a few seconds until that lifter bleeds down to self-adjust. Tighten the nut another 1/4 turn and wait again for the misfire to go away. Keep on doing that until the misfire no longer goes away. Typically that takes about 1 1/2 turns. Back the nut off just until the misfire clears up. For the final step back the nut off exactly half way from where it is now to where the clattering stopped earlier. That will put the plunger inside that lifter exactly in the middle of the lifter body. From there it can easily self-adjust longer to take up the slack when the valve train is cold and it can bleed down when valve train components expand when the engine gets real hot. Do that with every valve.

When the misfires occur as you tighten the nuts, don't go much more than 1/4 turn without giving the lifter some time to bleed down. The exhaust valves in particular are cooled when the valve seats and heat in the valve is transferred into the cylinder head. Running the nut down too quickly holds the valve open longer and allows it to get hotter, potentially hot enough to start to burn away.