Lack of Power

[gcdsn76]

I have a 67 383 running a 625 Street Demon with a mild cam and headers. The plugs were recently changed and I have a Mopar Electronic ignition.  The car seems to run okay with no noticeable bog or missing, but it doesn't seem to have as much power as it should have. Suggestions for any avenues to explore on why it seems to lack power would be appreciated.

[garner7555]

I'm not the best person to help you but I will give you a little advice.  I would say do a compression test on all 8 cylinders, then the experts on here can be even more helpful with that info.   

[lukedukem]

Did you notice this and that's why you changed plugs. Or did this start after the work was done

Luke

[myk]

What's the history of the engine?  Do you know it's specs?  What parts it's running inside?  Without knowing about the internals who knows what your engine is doing...

[crj1968]

Automatic?

[gcdsn76]

The engine is mostly stock internals and it's an automatic. It is not burning oil, but I will check the compression.

[LowDeck451]

Not trying to be smart or anything but, the secondaries are fully opening right? (only speaking from experience with my nephew's 'out of the box' Holley years ago) the secondary diaphragm spring (?) was too heavy. And yeah, like the others said, need more specs. 

[Challenger340]

The engine is mostly stock internals and it's an automatic. It is not burning oil, but I will check the compression.

Do you know what "stock" internals are present ? Pistons ? Camshaft ? which Heads ?
or,
Any history on the Engine ?
Chances are if it has been rebuilt, and Bored & Honed with new Pistons at some previous point in it's life ?, it may have a very low compression ratio, because most rebuilder style Pistons are terrible, and.... well.... that coupled with the equally poor rebuilder or RV style Camshafts... makes for well running, but very anemic 383 engines power-wise.
Which unfortunately, NO amount of Carb, Intake, Ignition or bolt-ons will overcome.

Compression test is a good place to start, warm it up good,
all 8 plugs out,
Ignition disabled,
Throttle plates wired wide open.....

4 needle bumps only per hole, record the first and last/final/4th bump.
Which, the first needle bump should be close to 75% of the 4th and final bump.