power-up 383 questions

[coronetcustom]

i got 1971-383 which i rebuilt year ago. i also put in hydraulic 272mopar.perf.cam, 750edelbrock carb and and performer intake. i´m about to install new edelbrock cylinder heads(all parts included). the engine is 1971-290hp/4bbl original and so is transmission etc. do i need to do anything for tranny/rear/torque converter? (got a-727, 8,3/4). i´m also a bit worried about piston rods since they are original(but checked and fine). i try to enjoy the car as much as possible, which means fast accelerations quite often.
thanks

[dwc43]

IF you are going to aluminum heads you need new pistons to increase the compression at least one point. The trans should be fine if it's been maintained along with the converter. That carb is a little small for what you have though.

[rumblefish360]

What is the comprsion ratio?

[coronetcustom]

i measured 9.4 in all cylinders.

[peg leg]

I recomend a better torque converter, with a higher stall speed, in the 2500 RPM range. Definitely put a shift kit in the trans. For gear ratio, 3.55 should make you happy, but 3.91 will make you really happy.
What intake are you going to use? The stockers can be pretty limiting, and I'd stay with a good dual plane. Try Edelbrock, Weiand or Mopar.

[coronetcustom]

thanks for torque converter and gear-ratio advice. i got transGo shift kit ready for installation and engine has new edelbrock performer 383 intake.

[rumblefish360]

Well, DW made a mention to something about piston replacement. While I do not agree on a piston replacement unless your rebuilding the engine, in which if you do later, I'd up the compresion then that way.

DW is making the recomendation due to aluminums heat disapating abilty over an iron head. The heat, which is power, escapes quicker through aluminum. This is why you normaly see a recomendation to raise the compresion ratio up 1 pt, to compinsate (SP!) bring back the lost heat through compresion.

Edelbrock heads for small block allready have a reduced chamber for this so nothing is truly needed, but seriously bennifited from a piston replacement.
A aluminum headed engine can handle a high ratio on pump gas without a big issue at all.

In a sense, your 9.4-1 is going to act alot like a 8.4-1 engine. You'll want to keep it a bit higher for better results.
This leaves you with leaving it alone, slightly low on compresion and live with it or one of two things to do to get it back.
Piston replacement or head milling.

[rumblefish360]

OH, 2 more cents.

You were better off with the stock iron heads preped and with the smaller valves.

[dave5711]

Originally Posted by rumblefish360

OH, 2 more cents.

You were better off with the stock iron heads preped and with the smaller valves.

I have to agree 100%

The 272 cam is well matched to the 9.4:1 comp, stock iron heads, perfomer intake(assuming not an rpm?)

The alum heads reduce effective comp. the chamber is smaller, but not enough.
BUT even worse, the runners on the heads are bigger. worse fuel atomisation, velocity, throttle response.

If you bump the converter to 3K, and the gears as recomended, you won't notice the losses.
If you bump the cam while you're in there(big heads, big intake, big cam, big gears), you'll probably see a hp gain, but the power band will be moved way up, so you'll have to spin it..

My .02 is leave the heads under the bench, untill you can bump it all, including the comp.