LA 318 advice

Here is just some math. for a 3.91 bore/ with a swept of 652cc
The cv (combustion chamber Volume) is assumed to be;
open chambers; 70heads/6.8 gasket/no eyes=76.8=A
Closed chambers; 60cc /6.8 gasket/no eyes =66.8cc=B
Below is a table
that compares the Scrs at the above cvs, at four various deck hts .
decks at .... cc are... ScrA ...... ScrB
.100 deck = 17.7cc = 7.9 ..........8.7
.075 deck=13.28=8.24 ...... 9.14
.050 deck = 9.84cc= 8.5 ........ 9.51
Zero deck=zero cc = 9.5 ........ 10.76

>For your application as long as you are on the primaries, power is hardly gonna matter. and
>As to fuel economy, at a particular speed with a given gear combination, you adjust the throttle opening, to get the power you need to cruise at that speed. Whether your Scr is high or low is of no concern, because Scr has NOTHING TO DO with cruising. Instead, it is EFFECTIVE Pressure that gets you the power....... which you adjust with the gas pedal. While it is true that a larger throttle opening usually means the engine will be less frugal, that is only true if you do not set the tune correctly.
>The point is, that not a chance would I spend money on pumping the Scr UP to get fuel economy that only requires a 5/1 Scr in the first place..
> a High Scr only comes into play as more power is required of a particular engine combination; ie, if you run out of power, or the bottom end gets soft, more CYLINDER PRESSURE is required. You can get that pressure in several ways;
1) a higher Scr
2) an earlier closing intake valve
3) more head flow
4) super-charging
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But, I gotta tell ya, swapping in a higher stall TC, say a 2800 versus an 1800, with no other changes, is gonna climb to near double the power out the crank, not by some miracle of physics, but by virtue of the additional rpm.
As an example; say your 318 is able to, at WOT, achieve 200ftlbs at the crank @1800rpm, which is 68hp. Whereas
the same 200ftlbs@2800 is 107hp. But whereas,
your 318 will not stall out at the same torque. More likely
it will have climbed to ~ 240@2800 with a 4bbl, which is then 128hp; and 128/68=plus 88%

There is nothing that you can do to a given engine, as regards cylinder pressure, short of supercharging it, that can make this huge a kick-in-the-keyster.

Therefore,
if you are not changing the ICA of your cam,
I see no good reason to destroy a perfectly good short block to get up to, a point and a half of compression, which barely makes a difference in your application.
If you keep going in the direction this thread is headed, your gonna spend a ton of money, only to find that for some 90% of the time, say from stall to 3500, you're only using less than 50% of the available power.
Wellchit, the highstall is gonna cover that no problem.

How so, you may ask?
Well, if the 318 gets up to 250 hp at WOT@ 4500pm, which is maybe 130hp@ 2800, and 68hp@ 1800; and has say the typical 2.76 gears for 2800=32mph; Suppose
the TC launched you at 128 hp right at Zero mph, and kept ripping at minimum 128hp all the way to 32mph,
Guess which one is getting up to 32 mph sooner!
I mean that's an over-simplification NOT favoring the TC, but you get the idea.
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Just so you know, I have done it both ways, and when I made this amazing TC discovery, many decades ago, I bought a couple of more 2800s, soon afterwards, Just to put on the shelf for the next A-body, and for many decades, every 318Mopar I bought, got one, as the first mod; and then, rear gears soon afterwards. I never again messed with the 318s except they almost always got a 4bbl, and dual exhaust. And I never again installed a 340 cam, I think I have about 3>4 of those, still stored in the attic.

In any case, whatever you decide to do;
Happy HotRodding.