View Full Version : Lack of power over 3000 rpm

08-12-2003, 12:22 PM
Is there anything in a 6AL box that could limit the output over 3000 RPM. Car just has no guts over 3000.
305 Chevy - blueprinted stocker engine, have changed trans, convertor, cam, looking for the problem.
Has all MSD Ign components, billit dist and MSD wires.

HELP !!!!

junkyard bronc rider
08-12-2003, 12:32 PM
when you say no guts, what should you be working with, as in perf. specs.

08-12-2003, 01:33 PM
we figure concervativly it should be running mid 13's at 100 to 102. 14.20's at 92 is way off where it should be. Have had this problem since day one.
Really want to know if this could be a box problem before i go buy another one. I bought the one i have new, but it took 2 years to get the car done.

junkyard bronc rider
08-13-2003, 03:29 AM
:) I have a couple of ideas. First, consider where your at,in relation to altitude, and climate. the dryer/hotter the air charge the harder the engine has to work to build power, thus the reverse is also true. I dont know were your E.T. figure is from, but you may want to figure that in. Secondly, you said you've changed the cam and the converter! STOP, you may very simply have to swap in a converter w/stall speed matched to the stall range of your cam. Hope these ideas are of some help. Need more info let me know.
GOOD LUCK: the junkyard bronc rider. :)

08-14-2003, 04:26 AM
I was told last night that there is a diode in the box that can go bad that effects the spark over 3000 rpm.

It's not weather thats effecting my car. The expected et's are very concervative. The way this car is built it should be in the low 13's. Both convertors are 8"

I've had this problem from day one, and been trying to find the problem for a year now.

I ordered a new box yesterday, guess thats the only way i'll find out.

08-18-2003, 09:52 AM
Normally, the MSD Unit will work or not, the performance output could only be affected by voltage input, if the voltage at higher RPM is decreased, then the output will also do the same. Although the voltage has to be below 10 volts in order to also affect the unit.