What to do to get more power from my motor

[TJKendall]

I have a 383 Magnum from a 1968 Chrysler Newport.  I rebuilt it for my 1970 Charger 500.
I Had the block Acid dipped and new frost plugs and then bored over .30.  Polished the crank. Oversized stock pistons. New oil pump and double roller timing chain set.  Comp Hydraulic Flat Tappet Cam Duration is 268 and 280 and  lobe separation is 110.0. I Have Stealth Aluminum Heads with Comp Steel Roller Rockers. Edelbrock Street Performer Intake and 600cfm Quickfuel Carb. Headman 3" Hooker headers. Changed out Distributer from points to Chrysler electric with balast and orange Box.   I am running stock mechanical fuel pump.  727 Auto Transmission and stock converter.  I have a huge lack in power. I can barely get a tire to spin. Huge bog.  My fuel tank was crap and rusted out. I have since replaced the fuel tank with new and lines and filter. Yet to try it but looking for what else I should do..

Some people say to do a 2500 stall converter but my car should perform a bit without should it not...?

Any help would be awesome.

[XH29N0G]

Welcome,  Others will have more specific information.  My thought would be to address the bog (as you imply) and to do this, I would start with the carburetor.  (I am assuming the plugs, ignition are fine and the timing is set appropriately - my understanding is that you could run something like 38 total unless your cr is high and what it likes at idle- again others will know).  Do you know what gear ratio you have in the rear?  For the carburetor, I would suggest giving quick fuel tech a call to ask about how the jetting, accelerator pump etc... might be set up.  You can do this on your own, but they should be able to give you a good starting point.

[TJKendall]

The rear end is a single tire fire..  It is the 8 3/4" with 3:23:1 gears.  It seems to take off not bad once it gets to about 2500- 3000 rpm.   For what I have put into this engine I should be burning tires off it?  Some say the 600cfm quickfuel is too small and others say it should work just fine..  I'm not drag racing but I just want to burn some rubber.. or atleast know I can if I want to... lol 

[c00nhunterjoe]

The cam is a bit large to expect the engine to be a tire burner with a stock converter and 3.23s. The 600 carb is kind of small also. All of that said, it should not be a turd like you describe. "Stock replacement pistons" could be anything. Do you have the part number of what was installed? If its got 8:1 pistons in it with aluminum heads, its going to take some tricky tuning to get some power out of it with your current setup.

[Challenger340]

The "stock" replacement Pistons, are very likely 1.848" Compression Distance units(about .080" down the hole @ TDC).... meaning, with Stealth heads advertised at 80 cc's(but actually closer to 83 CC's out of the Box), you have a barely 8.0:1 Compression Ratio.
Don't argue.... no point, but THAT is just fact no matter who says what.
With C.R. being a critical factor to Torque at low rpm's, and with the already very limited 3.38" Stroke of the 383, you very simply can NOT expect any kind of off idle power whatsoever.
To note,
that is one of the critical areas to address when building the 383's, being their poor low end Torque. They are revver's.... but inherently poor down low, which you have compounded the problem with those Pistons, further compounded by the aluminum heads which dissapate heat of combustion quicker.

You can try tuning out the low rpm Bog until the cows come home.... it won't work, with only very limited success at best.

About the only thing to do at this point, if you want some "snap" down low ? IMO, is to buy a stall Torque Convertor to allow the poor wee-83 to get a RUN up rpm-wise more into it's rpm range, when starting from a dead stop.
I would suggest something in an 11" High Stall be considered, which, even then it will be tough to get the low-pop 383 to flash up around 2500 rpm(on what are typically considered 3,000 stall Convertors), nonetheless, it will help immensely.
Once up at 3,000 rpm, I suspect your 383 probably does just fine... so you should be good to go.

Good luck with it

Bob @ rmp

[birdsandbees]

Take the modern radials off, put on a set of old bias plies and it will return to the tire burner you remember! 

[RollinThunder]

What is your intake manifold vacuum at a hot idle in Park?  And what rpm is it at idle? 
If I read your post correctly, you have the performer (not performer rpm) and this is an aluminum dual plane intake.  This is good for low-end torque.  Based on the spec's of the cam I'm guessing this is the XE268 comp cam, or similar.
My opinion is, the motor should hold at least 16 in-Hg of vacuum at 800 rpm, to be considered in good tune.  Another clue of a bad tune is more than a 80 rpm drop when you put it in gear with the brakes being held.

[BSB67]

Although the 1.84" CD piston is common, there are other pistons commonly used that are not as bad, including the 2315 which is 1.92".  So it could be as bad as suggested, but maybe not.  Second, you can eliminate the bog as it is a reflection of something not right in the ignition or carb tune or both, but even after it is fixed it still might be a turd down low.

The short of it is,  you next steps should be to get what you have now running correctly first.

You need to do the following:
1) Do a cylinder pressure test.
2) Get the piston part number if you can,
3) Get the ignition right,
4) Get the carb you have right,

Then you will know what you have now, and figure out what need to be done to get it where you want.