I've seen A LOT of posts about making HP with a 318-So why is it so ???

After reading a few pages of interaction here, and looking at my own 'B/RB/G3 Hemi' bias - I don't see an issue with a 318, if expectations are kept reasonable.

Expectations low, meaning 230 - 260 HP @ 5,000 RPM is a good place to start. We aren't talking about 'trick' builds to make this power: stock 7.5:1 CR (original engine) with a near factory replacement dual-plane (Edelbrock Performer), 600 - 650 Carburetor (Edelbrock or Holley), Small camshaft (215 - 230* @ .050 / .450" lift / 110-114 LSA), Longtube Headers, & open exhaust.

The same can be done to a 5.2/5.9 Magnum to make slightly more power, but they are getting to be near 30-years old as well. Most of these engines are worn completely out, will need a rebuild, and some (not all) have at least one cracked cylinder head. The bottom end might be fine however, but really it's the cylinder heads that were trouble on a lot of these engines.

We built a near identical engine to the above in a prior-MIL M880 Dodge (1977 W200) truck. I can tell you, it's an incredible difference overall in power over the factory 2-barrel setup with manifolds. We didn't touch the cylinder heads, only installed new valve springs.

Of course, anyone wanting to make more power with a 318 LA, would run a SFT camshaft around 235* @ .050 / .480-.500" lift / 108 LSA and a RPM Air-Gap manifold. I'm sure that would get 280 HP out of this combination and have no problem running with most 340's and 360's of this era. Lets be realistic, most of these original LA-engines are losing around 6% overall in power due to compression ratio alone, compared to a 9.5:1 typical (rebuilt) street engine with iron-heads.

A lot of people also need to keep in mind, that although these engines typically don't make a lot of power (especially compared to modern vehicles), they can still have a great power to weight ratio. You don't need to make 350-HP to have a nice, street driven car or truck. The lack of torque at lower engine speeds, allows most of the driveline parts to last for a very long time.

1977' Dodge W200 'Power Wagon' - 4,500 lbs w/ 250 HP (NET) - 0.0556 hp/lb
2015' Ram 2500 'Power Wagon' - 8,000 lbs w/ 410 HP (NET) - 0.0512 hp/lb