Well after 10 years of incredible informational arguments from our impressive members the consensus is the reason why the 360 is better than the 340 is because it is cheap.
Nobody is saying a 360 is better just because it's cheaper.
They're saying it's better because it's both cheaper *and* has more cubes.
You get more potential power from more cubes and it costs less. It's a win.
All things being equal which they never were.
To wit:
1. The better performance engine from the factory was the 340 but the 360 was cheaper.
Thats right, in stock configuration they never were equal. The 340 had the advantage.
But 50+ years has passed and most people expect to make more than the 275hp the high performance 340 engine made.
Any 50yo 340 or 360 LA engine with original heads/valves is probably going to be snagged out.
And those factory valves, springs etc are almost certainly gonna go straight in the trash and be replaced by something superior. (If not replacing heads with new aftermarket ones entirely)
That's $$$ you need to spend regardless of whether you are building a 340 or 360.
Can't get leaded petrol anymore, even if you found low mileage 340 heads for cheap, it'd still be time for new seats by default.
The 340's cylinder head advantage seriously just isn't there at all in reality.
I'd even say that reconditioning any factory cylinder head isn't worth it if you want performance. unless you can do the machining and port work yourself.
2. In order to unlock the performance potential of the 360 one must replace the pistons, the heads (or bigger valves like the 340 2.02 intakes), and replace the intake manifold with one such as the 1971-1973 340 intake. These changes are affordable to do because the 360 is cheaper.
Not necessarily, a junkyard $500 5.9 magnum with stock heads and pistons will make as much power as a freshened up 340, and would absolutely roast a 50yo one with a lot of mileage.
Sure, the 340 comes with a decent 4bbl intake.
But most people would be buying a superior aftermarket piece regardless of whether they have a 340 or 360 though.
Intake manifolds are literally the lowest hanging fruit in the quest for horsepower.
3. You can bore the 360 block to its maximum and it will result in the same bore as the 340. Throw a stroker kit on it and you got 408 cubes! Do the same procedure with a 340 block and you get 418 cubes! Everybody supporting the 360 because of its bigger factory displacement should now advocate the 340 block because it now has a bigger displacement than the stroker 360 block! But the 360 block is cheaper to start with.
If a 340 and 360 were comparable in price, a 340 block with stroker rotating assembly would be the hot item.
But 340 engines cost 3x-10x what a 360 does, depending on condition.
If you wanna pay an extra $1500+ for a 340 block that might give you the potential for an extra 8 cubic inches in a stroker configuration...I say go for it.
Personally I couldn't justify that.
I'd save $1500 and used it to pay for most of that stroker.
4. I skipped over the induction changes such as tunnel rams, cross rams, inline dual quads, turbo chargers, blowers, and N2O. The 360 is still cheaper.
All of these things cost the same whether they're bolted to a 340 LA or 360 LA, (and a 360 magnum too if you redrill to suit LA intakes)
but all of these will gain more horsepower on a 360ci engine than a 340ci with the same heads/cam/valvetrain etc.
Bottom line, the 340 is only the better choice if comparing stock engines.
