1973 340 Cam advice

If you really want to swap out that cam, I gotta tell you I'm no fan of 114* LSA cams
Using the OEM 268/276 cam specs, the DCR in an 8.4SCR engine goes from 6.74@128 psi to 7.03@135psi by simply closing up the LSA from the OEM of 114 to a custom at 108LSa.
The compression distance increases from 116* to 122*, and the
time spent in power extraction also increases by 6* from 104* to 110*,while
overlap increases from 44* to 56*
The powerband will become narrower, but the specific horsepower will become greater, and you get a few more yards travelled on a gallon of gas. Who knew 6*could do all that!
This may not be the cat's meow for a TF-automatic with a 59% 1-2 shift split. But it can be dynomite with a 4-speed. And that includes a city-car with something like 3.91s,lol.

A similar effect can be created by advancing the 114*LSA cam from the 110* factory setting to 104*, but this really messes up the exhaust cycle. This will reduce the power extraction to 98* and POOF! goes any fuel economy you mighta had. It also messes up the overlap cycle,by opening up the intake while there is still a lot of energy in the exhaust. With headers, a lot of fresh fuel charge can go straight across the piston and out into the header. With log-manifolds some of that exhaust can end up in the intake. So that's like a triple whammy to fuel economy. Quadruple if you include the 3.91s,lol.
But then if you are only gonna drive it 500 miles a year, then who cares.


But then, if you are only gonna drive it 500 miles a year, then why spend any money on it at all? The 2bbl will be running at it's WOT-rated capacity at about 2600rpm @ 100% VE. With an 8.4Scr engine running (guessing) up to 60%VE at say 3700 and with the 2.92s and a 2.66 low,this might be 37mph.
So this 2bbl might actually not top out until 3700rpm/37mph,still in first gear. Of course the engine won't stop revving or blow up or anything stupid like that when it tops out the 2bbl. No it will rev all the way to redline,just fine, and pull more than it's rated capacity while doing so.. It will just be missing maybe 20 or 30 hp up there. When you hit second gear (1.91), it will again pull strong all the way to about 52mph/3700again.
Of course a 500 or more cfm on that included manifold will pump up the 3700 to 5500 zone, at the top of first, taking first gear (2.66)all the way to 55 mph.

Order your 4bbl throttle cable bracket today,lol.