Carbed 914 Problem Options

[microsa]

I am doing some work on the 914 that I built and sold last year and have run
into something that has me stumped.
The car:
2056cc
WebbCam #86 grind (I think)
IDF 44s
Stock valves w/heavy duty springs (bus I think)
Carbs matched to intake, intake matched to heads, no porting, just 'cleaned
up'.
050 Dizzy w/electronic ignition (Compufire)
Taylor wires
Bosch Copper Plugs (new set)
MSD 6AL
Facet Fuel pump
Facet Pressure Regulator (set at 2psi)
Car has been running great for the past two years, then at last months
autocross, it started acting as if it was running into a rev limiter (goes
'soft') at about 5500 rpm instead of at the 6500 rpm 'pill' in the MSD box.
I first tried removing the pill which should remove any MSD induced rev
limit. Problem was still there. Checked all wiring and all looked fine, even
screwed in a new set of plugs at the autocross. Still fall on it's face at
5500 or so. Below 5500 the car is flawless.
Fast forward to this week. Took the MSD box out of the system, problem still
there and I noticed that it seemed to be intermittent; sometime it would rev
to 6500 the next time it would only go to 5500. Next I removed the CompuFire
and installed a new set of points. Problem still there. Installed new cap
and wires, no change. I next checked all the fuel filters (one before the
pump, one before the regulator) all clean, but I replaced them anyway. No
change in performance, still goes soft. Took the tops off the carbs to check
float bowls; all clean and levels are correct. Removed and cleaned all the
main and idle jets. I installed a new fuel pressure regulator and fuel pump.
No change. The car idles great and runs great up to 5500 rpm or so.
The odd thing is it feels exactly like a soft rev limiter.

Ideas?

TIA

Mike Allen
San Antonio, TX

[microsa]

Well, this is what I've done as of noon, CST:

The advance is all in by 1500 rpm so I don't think that is the problem. I
installed a new rotor a little while ago, no change. What ever happened, it happened all
at once. This car was running STRONG till this happened. It still runs
strong up to 5500 or so. The whole engine goes flat, not just one side.
Feels exactly like a MSD soft touch rev limiter, but the MSD box is no
longer in the system. I'll check valve clearance after it cools down, but
the motor is quiet so I can't imagine the valve clearance has opened up.
Hard to imagine valve springs as it seems to be affecting all 4 cylinders.

Once again here is all that I have replaced:
cap
rotor
points
plugs
all fuel filters

These actions have been taken:
idle,main and emulsion tubes have been removed and cleaned
timing has been checked
Taylor wire set has be ohm tested o.k.
advance mechanism in dizzy (050) has been checked for operation, appears to
be free and all in by 1500 rpm.
float levels checked
float bowl clean
fuel pressure steady at 2.5 lbs. (tried all the way from 1.5 to 4.0 lbs, no
change)

What am I missing? I checked with the astro-physics people, we are not
experiencing any unusually high sun-spot activity!

Mike Allen
Stumped in San Antonio