Performer RPM Cylinder Heads For S/B Chrysler

So let's talk about TM
Say your 273 makes 100 ftlbs at 1750 stall speed, and you have a 904, and you have 2.76 rear gears.So on the start line you will have 100x2.45(low-gear)x2.76( in the back)=676ftlbs to launch with. Well that's pretty sorryazz. To really get moving you need over 1000 with a 3400 pound pkg. To fry the tires you will need maybe 1400 with skinny tires.
So you can get there in several ways
1) a bigger engine, or
1B) an engine that thinks it's bigger
2) a higher stall rpm
3) more TM
4) less weight
5) supercharging the one you got
So let's say you make no other changes except installing a 318 which makes 120 ftlbs at the same 1750rpm. this maths out to 811ftlbs, which is plus 20%.
But let's say instead that with same 273engine, you increased the stall rpm to achieve the same 120ftlbs, Now you're blasting off like a 318 with plus 20% Torque at the start line. However, don't get too excited, cuz the 45 cube difference will quickly become apparent with rising speed and rpm.
But let's say you put 3.55s in the back and go back to a 1750 TC. This maths out to 870ftlbs. But hang on, this 28% TM advantage is carried all the way thru the gear and every gear. That's a good thing right? Well yes it is if you don't mind the plus 28% cruising rpm.
But we're still not kissing the magic 1000 ftlbs. So what if we add the TC back in? Well that maths out to 120 x 2.45 x 3.55=1044! badaboom! You can now show taillights to any stock 318 running 2.76s in a similar weight chassis.
But we're not finished yet. There is a deep-low trans you can score in the junkyard called the A999, which externally is identical to your 904, but it has a 2.74 low first gear. What can we do with that? Well let's keep the 3.55s and the higher stall TC as in the previous combo and sub in the 2.74 lowgear. This maths out to 1167 ftlbs.
And we haven't touched the engine yet.
But let's say 1167 is more than you need. Lets take a bit of rear gear out, say going to 3.23s to get the hi-way buzzzzzz down. This maths out to 1062ftlbs.
Or say the hi-stall was not to your liking and you went back to the stocker. This maths to 885ftlbs.Well you might want the 3.55s back to get 973,pretty close.
But lets back up;
Lets put a 4bbl on there. and pick up 10 ftlbs at 1750 rpm, and put the 3.23s back in, to get 974ftlbs. Ok, how about headers, or in your case just hi-po logs and dual exhaust, add another 10 at 1750, now we're back up to 1167, so the 3.23s can return, for 1071ftlbs.
But suppose you don't like the 1-2 split of that A998, cuz admittedly it's pretty wide for a 273. Ok so lets work it with the 4bbl273 with hi-po logs, that 2.45 low of the A904, plus the higher stall, cuz they're just so much fun,and 3.23s the max that you have decided to run. Ok then;140 x 2.45 x 3.23=1108; and you're spinning tires.
The sweet part of this combo, is the TC and 4bbl will cover the hole from stall to peak torque, and the gears will make a difference of plus 17% in every gear.
So to recap, this combo is not for racing,period ; as soon as you get into third gear you'll know why. The engine is just too small. No, this is a first gear runner, to about 40 mph.
And when you pull out to pass at 60, when she downshifts to second and the secondaries open, something is finally going to happen!
So what's all this gonna cost. Well a 4bbl and intake plus hi-po logs and a 3.23 gearset installed, plus the fun TC, Ima guessing , change back from $2Gs. But here's the kicker, you only need to install as much as you need until the performance gets to the level you want.
I would install them in this order; gears first, then the TC, then free-flowing exhaust and the 4bbl dead last. You could swap the exhaust and 4bbl, but I don't think you'll see much of an improvement with a 4bbl into a single exhaust; they have kindof a symbiotic relationship with better results when the exhaust is opened up first.
Altho on you combo, I'm not so sure.
I tell you what, do the 4bbl first and then measure the back pressure in the pipe before it gets to the muffler. If it's over 4psi, make some duals, and retest.. If it's under 2psi at full-load WOT, leave it alone, you won't gain much for the money spent. Between 2 and 4 is a judgement call.Drive it for a week with the pressure gauge mounted somewhere you can see it . Then just keep an eye on it whenever you get to pressing the go-pedal. If it generally stays below 3 psi, I'd pass on the hi-flo exhaust, and save a buncha money. Now you're into it for maybe $1200

I did all this a couple of times allbeit with a teener, and it turned out great! I used 3.55s, a 2800 and the A998 with a factory TQ. One had headers and 3"full length duals which sounded awesome. The teener handled the wide-splits of the A998 OK.The teener was otherwise stock and was maybe a little tired. This in a 3650 car.