2.76 open to 3.55 Sure Grip...expectations too high?

Righty Tighty said
but I’m not sure it’s worth the trouble at this point in time.

IMO: It absolutely will be worth it.
Another thing that will perk your combo up is more cylinder pressure. But to do some math, we kindof need to know what your current pressure is, so we can know how much room is in the combo.
But we can fool around with the math.
IIRC you said your cam is 256/262/112. For my calcs I will assume it is in at +4 or 4* advanced, so in at 108*.
And it's a reman 318LA, so say 3.93x3.315
And I;m gonna estimate an Scr of 8.3
And Wiki says you are at 2700ft. That is a big deal because compared to sealevel, your pressure will be down about 14psi
Ok so plugging all those numbers in to the Wallace Calculator I get;
Ica of 56*,and 2700ft
Static compression ratio of 8.3:1.
Effective stroke is 2.74 inches.
Your dynamic compression ratio is 7.03:1 .
Your dynamic cranking pressure is 123.98 PSI.
V/P (Volume to Pressure Index) is 99 .
The numbers of importance are;
Dcr of 7.03, and V/P of 99
The Dcr number for iron heads needs to be closer to 8.0 for maximum low rpm torque.
Read about VP here V/P Index Calculation
The VP number needs to be about 114, just to match a regular low-compression 318 at say 800ft elevation. But the fun don't start until over 130.
Now;
on the street, power don't mean a whole lot
Having the right power at the right time is what it IS about. I like the power to be right healthy at 30/35 mph, so that when I floor it, the dang thing takes off hard.
The 904 comes with ratios of 2.45-1.45-1.00
And your rear is a 3.55,
and your tires in a Valiant, like your Avatar, have to be more like 265/55-15s max, which come in around 26.5.. which times pi (3.1416) = a roll-out of 83.25. So then, the math is ;
rpm= (mph x1056x all the gears) / tire roll-out, and thus
rpm for 32mph, is 32 x1056x2.45x3.55/ 83.25=3530 at zero slip.
The 1-2 split is 1.45/2.45=.592 so in second gear, 32 mph will be 3530 x.592=2090. Assuming 8% slip cruising in Second, your tach might br reading 2260, that sounds pretty good so far.
At 32 mph; when the trans downshifts into First the slip might be 30%,I'm guessing, so the tach might read 3530 x1.3=4590. Now that's a lil high for your 262advertized cam, which doesn't have a lot of headroom there. But at 4590 it should move out real hard.
I'm gonna guess that 262 cam might be about [email protected], and the power-peak on that might be 4900. With your heads, it might carry that out say 200rpm, and say 500 out, the power is crashing, so let's call the shift point to be 5400. In first gear, that is ~37.7mph. So as you can see, your 3.55s are a lil steep, for a downshift at 32 mph, because in the blink of an eye, just 6 mph higher, it will be time to shift.
So let's start over and work the numbers backwards.
For a power peak of 4900, the torque peak will be about 3400, so at what mph does this occur in first gear? At 30% slip again, my math says ~24mph. So 24mph is on the torque peak, so about the minimum roadspeed to floor it at, for good acceleration. Now we have 3 data points; 24 the minimum, 37.7 is time to shift, and 32 mph is a lil high. Lets try 26mph, and I get 3730 still at 30% slip. Ok so there you go; for your combo, slamming the pedal down at 26mph, should get you RapidTransit in First gear@3730rpm; and you won't have to shift until 5400/37.7mph.
So what happens at the shift into Second at 37.7 mph? Well the rpm drops to 59% or~3190. Now yur in trouble. Your low-pressure engine, with no help from the TC, is quite a bit off the cam, so it will struggle to get back up on it. 3400 in Second doesn't come until 44.3mph, so you will have a hole in performance between 37.7 and 44.3 mph, before the engine starts waking yo again. But, in second gear, the power peak of 4900 doesn't come around again until 62mph, and 5200 is 66.4
So, actually that cam is finishing well. I mean you could go down one size and not miss it, cuz now the cam would be done at 60ish.
How about passing gear?
Say you are motoring along at 60= ~2800, and you need to pass someone doing 55. So from 55=2570 you hit it. The trans downshifts into second, and the Rs climb to 55=4300 and you are away. Second will get you up to 69 mph/5400. He that's pretty good...

So as can be seen, the combo of the 256/262 cam and 3.55s are doing pretty good for you. The only problems are the lack of giddy-up off the starting pad, and the hole from 37.7 to 44.3 . The starting pad you can solve with stall, but stall cannot help with the hole. The hole can only be solved with more cylinder pressure.
In a given engine, there are about three ways to get more pressure;
1) taller pistons, or
2) machining the heads or decks, or installing a thinner head gasket.or
3) an earlier closing intake valve.

Of the three, a new cam is probably the cheapest.
The numbers above say that you can drop one size at .050. But the you really need a bigger change than that. So a swap to a solid lifter is the way to go. In your case; swapping the [email protected] to say 208, while simultaneousy swapping to a solid, could get your advertised down 2 sizes, now yur talking.
Lets say you found a 208*@.050 after lashing cam, and say after lashing the advertised was 248, Lets say 248/256/108+2,SFT , that will set up with an Ica of 50*
and I get;
Ica of 50*/2700ft
Static compression ratio of 8.3:1.
Effective stroke is 2.86 inches.
Your dynamic compression ratio is 7.30:1 .
Your dynamic cranking pressure is 130.93 PSI.
V/P (Volume to Pressure Index) is 109
Well it's better but not really what I'm after. And not a big enough difference to spend all that money on.

Lets put some hi-compression pistons in there and get them up to Zero-deck, whatever it takes.
So we're gonna go from an estimated 90cc total chambers to an estimated 77cc, which will give you an Scr of 9.6.. And we'll leave your current cam in there.

Ica of 56*/2700 ft
Static compression ratio of 9.6:1.
Effective stroke is 2.74 inches.
Your dynamic compression ratio is 8.11:1 .
Your dynamic cranking pressure is 152.11 PSI.
V/P (Volume to Pressure Index) is 121
BadaBoom!, your Dcr is now up, your Pressure is up, and your Vp is approaching 5.2M status(124)
With "closed" chamber 302s your Quench is now whatever your gasket is, so yo actually have room for a lil more pressure. But 152psi will still burn 87 gas. This is what I was looking for.
It ain't great, but at 2700 ft, it can't get much better.
Since the engine would have to be out for this, I would combine this with a 2800TC..
Now I suppose it is possible that the pistons currently in the engine are already closer to the decks, then the mediocre heights of the stockers, so that would open up other possibilities of pumping up the pressure. The key in my calcs was the 77CC total chamber volume;there are lots of ways to get to there; It doesn't have to be pistons. But I just like to spend my money on things I can touch,lol. I am not fond of machining everything in sight. Too often it ends up screwing with the intake fitment. And it always leads to new pushrods.
Remember I am just fooling around with the math here, killing time until we see more of your combo.
Happy hotRoddingi