I’m wondering what a should expect for hp?
At 7.8 Scr, and say an ICA of 64 degrees,
You might expect cranking cylinder pressure of 115psi @900ft elevation.
You might expect the bottom end to feel only a lil stronger than a slanty.
The only way past this is;
with a moderate stall converter and
Hi-perf rear gears, and
Forget about taking on passengers.
Point it downhill and floor it, but don't tell the wife you'll be right back, cuz it's uphill coming home.
Listen, for a street car, with street gears and a factory stall converter, having 245 hp at 4800rpm is almost meaningless, and pales in comparison to having 245 ftlbs of torque right off idle, and 400 by 3000.
You can't get that with the combo you describe.
Imagine you are sitting atta stoplight.
Imagine you have 3.23 gears, and an 1800 stall convertor, that musters a ratio of 1.5 for however brief a moment, at stall.
Imagine yur 7.8 hotrod makes 240 ftlbs at 1800, which is 82 horsepower.
Imagine you floor it, and into the axles goes
240 x1.5 x2.45 x3.23= 2850 ftlbs.
>Now suppose all you do is replace that convertor, for a 2800 stall and say it makes a ratio of 1.7 , and say your anemic 360 makes 280ftlbs at 2800, which is 149hp. Into the rear axles go
280 x1.7 x2.45 x3.23= 3767 ftlbs. which is 32% more torque.
> let's add 3.91s; into the rear axles go
280 x1.7 x2.45 x3.91= 4560 ftlbs, which is an increase of another 21%
Now imagine, you pumped that 360 up to 195 ftlbs and are running alloy heads with a modest cam that has an Ica of 60 degrees, and now yur running 3.91s and a 2800 stall. Say this engine makes 380 flbs at 2800, which is 200hp. and say your new converter musters a ratio of 1.7. Into the rear axles go
380 x 1.7 x 2.45 x3.91= 6188 ftlbs, which is a further increase of 35.7%
now yur talking frying tires and billowing smoke.
Ok I know, how about using this HO 360 with the stock 1800 TC and 3.23s. Suppose at 1800 that HO 360 now puts out 320ftlbs, Into the rear axles goes
320 x 1.6 x2.45 x3.23= 4050 ftlbs
compared to the 2850 that you started with, this is plus 42%
So now, look at the percentage increases, and decide for yourself, which is right for you.
Please note, all Torque numbers I have used were pulled out of my imagination, to help illustrate this concept. Your results will vary.
IMHO
on the street, 1 ftlb per cubic inch at stall, which you are passing thru, many times on every outing, is infinitely more fun than 1hp per cubic inch at say 5000rpm, which rpm, you only get to enjoy but once on your way to the speed limit.
The convertor, the trans, and the rear-end, are all just torque-multipliers; and so, if yur engine is a turd, you'll just have varying amounts of turds with varying amounts of multiplication.
An SBM engine with just 115psi of CCP is a turd. even 135 is still a turd at low-rpm. About the best you can run with iron heads is 165psi and yur not gunna run that with a non-quench design. Whereas ;
With alloy heads, 185psi is easy, and I have run 195psi still on 87E10, with no signs of distress. There are a few guys on FABO running a lil more, usually in strokers, on best pumpgas.
While it's true that you don't need cylinder pressure at the racetrack,
and you don't need pressure for a DD; Nor for hiway travel.
But, it's a myth that you don't need cylinder pressure for a well-balanced hotrod. Every time a street-engine is asked to increase in rpm, it gets there by employing a higher effective cylinder pressure. If 115psi is all you got, getting to a higher rpm takes more time, which is, the bane of hotrodding.
