all good suggestions above mostly
basics
air pressure
different track conditions/weather
track temp/prep
shocks settings, for the proper conditions
valve lash/preload or bent/loose pushrod/s (?)
camshaft going away (hope not)
run the valves, is the best way to keep ontop of it
timing
just spitballing here
different fuels, even just diferent brands
&/or old/er fuel can wreak havoc too
clogged or partially clogged fuel filters,
should be 1 by the tank/cell & one by the carb/s
maybe the fuel pump not keeping up
does it have a regulator (by-pass IMPO is the best) is it still the same
do you know (?)
what your fuel pressure "actually is" going down track WOT
& in the traps
different weather, temps, RAD, humidity, the corrected altitude
tires pressure/traction or they are just going away
any of the above can effect it
Generally speaking
valve lash can affect it too
too loose will generally lose some up-top/MPH
your HP is your MPH, losing MPH is usually 'giving up' HP,
if all else is the same
ET is basically torque & that's how your car specifically works
suspension tires gears converter & that gets to the 330' mark,
where much of the ET, can be lost or gained
valve springs going away
basically losing control of the valves &/or valve-float, kills power
valve springs are finicky deals, some go away fast
some seem to last for a long time & cost/price isn't always the reasoning
seems like a real crapshoot
voltage, plugs, cap, rotor, wires, coil, ignition box/computer controls
anything in the ignition system
anything with more resistance
just because they (parts) are new (newish) doesn't mean they are good
or any misfiring
no matter how minimal, can affect the performance
I've had NEW ****, right out of the box, be bad & run bad
pull plugs after a clean shutoff
(not a bunch of idling around on them)
& do a reading
see what it wants, if you don't know how
good rule of thumb
A 300rpm + or - off, at launch or at shift points,
can be a huge change
in either direction, could be better or worse
some cars are far more temperamental than others
do you have a AFR gauge
something 12.8 at WOT is good,
about right where you should be, the sweet spot
on Gas/pump or race gas
11.? (or lower #) is too fat at WOT
13.? (or higher #) is too lean at WOT
idle can be 13:1 but not at WOT, not on any race engine running GAS
(different deal & #s on E85 or Methanol/Alcohol)
too lean or too fat can affect it that much too
Jetting for good air (especially mineshaft good, cool & dense)
vs bad air (hot humid wet) is/can be vastly different
do all the basics 1st check the simplest things
check the total timing, **** can change
check & see if you have any arching/cross-firing going on
run the valves cold & hot, see what it's actually doing
see if any one cylinder is having to be adjusted more than another
lots of stuff can go on there, some lil' changes can do weird stuff
check all the grounds on the car too, ignition & battery depends on it
all can & will affect the times
I'd also
Do a leak-down test, and see where it's losing compression/air
if it is, going into the pan, it's rings more than likely (possibly piston/s)
if you hear it thru the carb/intake, it's intake valves,
if lash or preload is adjusted properly
if you hear it thru the exhaust more than likely exhaust valves,
if lash or preload is adjusted properly
the trans is the major change
since you last ran it, it seems
I'd look there too
maybe parasitic drag on something (?)
the converter could be going away too
tires, shock settings, etc. etc. etc.
racecars wear out, sometimes even run to run
gotta keep on top of it, to know where you have something going away
keep a detailed log of conditions, RAD, weather,
specific tune & different tracks settings
I hope for your sake, it's nothing major
good luck
