different 318 question

Are you saying your teener cannot drive faster than 70 mph in any gear? And does not backfire,missfire or otherwise misbehave? That sure sounds like either;
1) the carb is only opening halfway on the primaries, or
2) bad cam timing/ very low cylinder pressure, or
3) a restricted exhaust, or
4) no ignition advance whatsoever, or or
5) the engine load is ridiculously huge,lol.kidding; you'd have to be towing a 10 ft tall 40ft long 5th wheel trailer.
Together with the other statement, about just makes noise, I think I'd be checking the carb opening first cuz that's easy,then the ignition timing mechanisms,then a compression test,Hyup, then a pressure test on the exhaust system, and then the cam timing dead last,along with the lobes. These are in order of complexity and time to perform.

Or are you saying it will not rev past 3500? This sounds like valve float/lifter pump-up, or plugged exhaust

Here's a tip; if the cam timing is seriously retarded, someone will have turned the speed screw waaaay up and cranked a bunch of initial timing into it. The engine will usually be very hard to start no matter how you set the choke. And of course the cylinder pressure will be very low, perhaps less than 50psi..... on all cylinders.... so yes, it will be interesting to see the pressure results.