Slow after 5000rpm

[kjalltrac]

I believe my car has 11.9s in it without nitrous, but it just feel slow after 5000rpm during racing so I just shifts around 4800-5200rpm. I can't figure out why?
Any ideas?
Most of the spec is below.
12.8- 13.2 afr during wot.
35 deg timing
Open cut outs
Velocity stack



kjalltrac said: ↑
12.4769sec 106mph
60ft 1.738
New personal best
The engine feels slow after 5000rpm?
Budget 440
L2355f stock bore pistons
Edelbrock E-street heads
Headman 1 3/4 headers
3" exhaust with mufflers that necks down to 2 1/4" inside
Edelbrock rpm dual plane intake
Quickfuel 850 dp with electric choke
Comp cam hydraulic 284h cam
10.1 comp

8 3/4 with 3.73 gears
Tf727 manual revers pattern
Hughes 3000 stall converter
Ss springs
10/90 front shocks
26" x 9" hoosier slicks

Shifts at 5000-5500 rpm
This was in 85-95 degrees heat
Full steel car with bench seat

View attachment 628271
New personal best. 1.74 60 foot 7.78/88.3mph @ 1/8
12.24/108.4mph @1/4
Colder weather this time, new mechanic fuel pump with new larger fuel lines and open cut outs.
Shifting at 5000rpm, still makes little power over 5000rpm,can't figure out why?

However I managed to run 7.62/91.23mph @ 1/8 and 11.915/113.145mph by adding 100hp nitrous. Still 1.74sec 60 foot

 

[Lefty71]

Id say heads are becoming the bottleneck, and it's time to move up to something with Max Wedge sized ports, which of course will cause a ripple effect on some of your other parts in the combo as well, like cam and converter. HTH, Lefty71

 

[Frank Mopar]

Try running it with the cutouts closed.

 

[BSB67]

First guess, your valve train is losing control. You should be closer to 5800 is my guess. Have you tried shifting at higher levels with the cut-outs open. Internal muffler collapse will suck power and rpm in a big way, but should not be an issue with the cut-outs open.

As a side note, tune your jetting to max mph, not to a gauge number - but not the problem you're describing..

What's the car weigh?

 

[kjalltrac]

Try running it with the cutouts closed.

Tried that, went slower

 

[kjalltrac]

First guess, your valve train is losing control. You should be closer to 5800 is my guess. Have you tried shifting at higher levels with the cut-outs open. Internal muffler collapse will suck power and rpm in a big way, but should not be an issue with the cut-outs open.

As a side note, tune your jetting to max mph, not to a gauge number - but not the problem you're describing..

What's the car weigh?

No use shifting over 5000rpm it pulls hard to 5000rpm, after 5000 it just won't accelerate as hard. Acts the same with and without the cutouts.
The car has stock weight around 3700-3800lbs

 

[BSB67]

So I'll stick with valve train then.

My past motor made more power, with a much smaller cam and lower flowing factory heads than yours. I shifted at 5500.

 

[Frank Mopar]

I run the same cam with 440 Source heads and 750 AED carb. Open headers with extensions.

1/8 mile. Shift at 53-5400 Traps out 55-5700 rpm. Runs mid 7:20’s @ 93 mph

 

[BSB67]

You know, looking at your 1/8 mile and 1/4 mile numbers, and despite the new fuel delivery related stuff you have, it could be fuel. Have you put a fuel pressure gauge on that you can read going through the traps?

 

[sclee440]

I'd go with valve float first, fuel supply second.

 

[R413]

No cam info. What cam is it? What rocker arms? Did you degree the cam?
What ignition system?
Sounds like cam is too small or cam timing is advanced.

 

[kjalltrac]

No cam info. What cam is it? What rocker arms? Did you degree the cam?
What ignition system?
Sounds like cam is too small or cam timing is advanced.

Yes I degreed the cam straight up I believe at 107 degrees (3 years ago if my memory serves me right)
Adjustable rockers set at 1/4 turn.
Using the recommended valve springs.
Msd 6a with chrysler electronic dizzy and msd anti vibrate coil.

 

[PRHeads]

What part number springs, and set up at what height?

What ratio rockers?

For the most part, unless the springs are flat out not providing enough load for the desired rpm....... with a hyd cam..... you’re pretty much at the mercy of what the bleed rate is with your particular set of lifters.

 

[Frank Mopar]

E street heads have approx 320 spring pressure. Thats not too much for the lifters and the cam is plenty at 507 lift

Not sure how good those e steets flow but the spec on them is 5500

 

[PRHeads]

What he said was:

Using the recommended valve springs.

I would have used the springs that came on the heads.

 

[kjalltrac]

E street heads have approx 320 spring pressure. Thats not too much for the lifters and the cam is plenty at 507 lift

Not sure how good those e steets flow but the spec on them is 5500

These heads have been cleaned up with a light bowl work, gasket match and back cut valves.
They should flow enough to support 500-550hp i think

 

[kjalltrac]

What he said was:



I would have used the springs that came on the heads.

Tried that last year, still the same

 

[kjalltrac]

My suspects are either that I've reached the limitation of the cam/lifters or maby the ignition box.
Might just upgrade to a solid cam and a new ignition box this winter

 

[PRHeads]

It’s not likely the MSD 6A.

The solid cam should cure it.

71 Charger, 3900lbs race weight, 446, KB flat tops, zero deck, ootb RPM heads, SD intake, 850DP, 1-7/8” headers, 4.10’s, 10” Dynamic, slicks...... 11.70’s in decent air.
Best ever 11.66.
Comp XS282S, ductile 1.5 rockers.
Made right at 500hp on the dyno.

Been running strong since 2005.

Here a little hotter one:
Short block is basically the same, bigger cam, bowl ported Sidewinders, RPM intake, QFT SS830 carb, Mancini 1.5 rockers, tested with bigger headers.

 

[AndersonTommy]

Your heads, cam and setup is giving you the max effort.
You wont find any more power with that combination.
Dont waste your money on a new ignition box.
It is what it is.

My suspects are either that I've reached the limitation of the cam/lifters or maby the ignition box.
Might just upgrade to a solid cam and a new ignition box this winter