Help Please, Performance Issue

[LEMOOREACE]

318ci w/stock short block and heads
Comp Cams XE256H Duration 256/268  Lift447/455
Edelbrock Performer Intake
Chrysler Electronic Ignition Orange Box w/timing set at somewhere around 16 initial and 34 advanced if I remember right
Road Demon 625cfm Vac Sec Carb.

Issue...  RPMs just wont wake up until she swings above 5200, just seems sluggish, a really slow long pull but all of a sudden "WHAM" RPMs jump and she really starts to pull hard like it just woke up... but then I have to shift because I'm really up on the RPMs..

First I thought maybe the secondaries weren't opening up fast enough so changed the spring to a yellow and not much change...
Yellow spring = 1635 starts opening, full open at 5750  Two steps down from the standard spring.

Plugs are light brown, not very dark brown, not wet either, perhaps just a tad on the lean side

Oh, my vacuum is a little erratic too...  rapid fluttering 1-2 inches

Still haven't upgraded the gears and I'm running 2:73s, I know that wont get her up there fast, but I can still tell this is a motor issue.. 

What would make her pull slow and then just wake up suddenly at RPM?  I mean, I can tell there's some good HP just trying to get out but its held back..

[hemiken]

Sounds like it could be ditributor related to me, sometimes you can have sticky weights inside your dizzy and most the time it is a case of spring weights being too heavy and when spinning at a high revolution they open to where is needed to change the curve and let your engine rev like their is no tomorrow.
Have a performance shop look at your dizzy and see if it needs spinning up to suite what your needs are
Good place to start

[Chryco Psycho]

Chevy cam lobe lots of duration / no lift , + small displacemnet ..............  try a Lunati Voodoo
with less duration & more lift this will increase compression lower down making the engine more responsive & will not lose power higher up 

[LEMOOREACE]

The disttibuter idea had crossed my mind (stuck mechanism, not advancing), the cam I get, but does not speak to the symptoms.  The power up top is there, but comes on like I threw a switch, and only for a few seconds before I have to shift.  Also,seems intermittent as well.  Happens when I hold the gas to the floor but not every time. 

I just put the top together recently and at first was thinking I should be seeing more performance gain but then felt comfortable with the outcome, but then I felt it "wake up" at high RPM and thought , where is that power spike/surge coming from, and why am I not seeing it every time I punch it, and why not through the entire pull?

[hemiken]

Have someone look at the dizzy and go from their
Get back when you have and see if that was the problem, does not quite sound like valve springs going off yet........

[LEMOOREACE]

Springs new, cam matched.  Car has no off idle hesitation whatsoever either.  It simply feels much like it did with the original stock setup with the 2bbl.  That's why when I felt it wake up I thought, that's the power increase I would have expected to have seen/felt after the upgrades.  So I just want to figure out how to make that power the full pull.  Really, it's like an instant hard pull change for a flash, then I have to shift. 

[hemiken]

It really sounds like your dizzy is giving you curry, have it checked and spun up, it will be a beast from idle on then even with that chevy grind camshaft you have in it

[LEMOOREACE]

Tore into the dizzy and compared the mechanical advance mechanism to another spare and everything seems to be functionally ok.  Added a little grease to smooth the operation for good measure.  Re-installed and reset timing 16/32adv.  No change. 

Then I checked the secondaries of the carb and they ARE functioning under a no load condition (snapping the throttle, watching them with an inspection mirror).   I dont think they are opening under load though (at least not full time as layed out in my previous posts).  It may be I'm not producing enough vacuum pull off the primaries under load.  I will try the "paper clip trick" on the seconday vacuume linkage under load soon to verify, but I'm 90% convinced and heres why....

I think I'm right on the edge of breaking that barrier but I suspect my stock 318 heads arent breathing enough and the stock exhaust manifolds are also restricting the amount of primary carb vaccuum at RPM.   I think if I went to a 550cfm I might be better off (currently have a 625 road demon which are known to pull more CFM than advertized).   

I do have a 600 Edelbrock a can try which ahs much smaller primaries (spreadbore) but I hate to screw with the carb linkage and fuel line changes needed just to test it out.  Maybe this weekend if the wife allows..   Otherwise I think its time to machine/prep the 340 block...   

[hemiken]

A visual inspection of the dizzy will not suffice i am sorry to say old mate you have to get it spun by a performance shop, they have the equipment to check it, it is to do with bob wieghts and springs internally. At least go down and have a talk with an engine performance shop and have a talk with them, the majority are very helpful as it is in their best interest to be so as they do not know when the next guy who wants to spend big is coming in, and it coul djust be you.

[Aussie Challenger]

As soon as I read this I was thinking delayed secondaries coming, if only running on primaries it will give some get up and go but then when the secondaries come off you go. Yes sticking weights will cause problems but they usually stay fully advanced or non at all.   

[LEMOOREACE]

As soon as I read this I was thinking delayed secondaries coming, if only running on primaries it will give some get up and go but then when the secondaries come off you go. Yes sticking weights will cause problems but they usually stay fully advanced or non at all.   

And that's how it "feels" too.. 

[erat340]

Neil is right. too much cam, thats how mine ran with the 60403 I now run the 60401 (10200701), bad azz low end torque. Remember, build for your RPM desired range.

[LEMOOREACE]

Neil is right. too much cam, thats how mine ran with the 60403 I now run the 60401 (10200701), bad azz low end torque. Remember, build for your RPM desired range.

I have less cam than you for the most part.  The slightest bit of duration on the exhaust side.

Your cam 256/262, Lift .454/.475


My cam   256/268  Lift .447/455  "HYDRAULIC: Strong torque through low end and mid-range, good idle. 

your first cam choice was outrageous if your motor is as close to stock as mine is.

I found the problem anyway, its in the dizzy...  I had it spun up, the vacuum can was dead, and the mech curve not enough.  New parts on the way, already curved for the car.  Beware of Craigslist parts...