Intro and SB Chev Recommendations...

[Doug Dayson]

Hello all...my name is Doug Dayson...I live in the San Francisco Bay Area in
CA...I'm a musician/audio engineer/producer and software engineer by trade...

I'm currently researching converting my modified 71 Corvette Coupe to
EFI...mostly because I run around with a club of people with newer Vettes that are
injected and when we get into higher altitudes I can't compete w/o rejetting
(which is a hassle) so...

The Vette weighs 3200lbs with a half a tank and no driver...it has a "stock short
rod" 406ci/375hp small block chev with TFS Aluminum Heads...Edlebrock
Performer Manifold and modified Q-Jet carb...1 5/8" X 3" headers...hyd flat
tappet cam timing is 218 @ .050 with a 110 LSA and .485 lift...it currently
makes around 450 ft/lbs at 4000 rpm and 375 at 5000 rpm (all gross at the
crank)...BTW it's already been converted to HEI ignition...

It has a 89 700R4 four speed automatic trans with a 3.08 rear gear and 25.5"
diameter X 8.5" wide tires...it's best at Searspoint Dragstrip (330 ft) has
been a 12.87 at 112 on street tires (shifted at 5500 rpm)...amazing enough it
does on average 19 mpg at cruise with the carb "IF" I keep my foot out of
it (thanks to the OD and Lock-up Torque Converter)...a pretty good all around
street motor...idles good...gets decent
mileage...goes good etc...I guess I'm looking mostly to keep the same power
curve (or better) and enjoy the increased driveability and economy that EFI
can produce!

Also of note...it's now smog exempt...though I'd imagine that any good EFI
setup will improve tailpipe emissions which is good!

And...hoping to do this swap with the engine in the car...so no engine dyno
time...could do chassis dyno though if needed...expensive though!

After all...as a pricing guideline..for $3700 you can get a "brand new"
complete GM LT-4  350ci Crate motor (330 Hp Net) with GM EFI...

So...with the above in mind (including my status as a EFI
Newbie)...recommendations (for hopefully) under $2K complete on a conversion concept?

1) TBI or MPI...one issue is my fuel tank return line enters the tank up high
(above the normal fuel level...hoping to not replumb the tank)...would this be
a problem with MPI's higher fuel pressures vs TBI's lower pressures?

2) Agreed...the Accel Super Ram would make the best performance...BUT...too
expensive...might not fit under hood...would probably kill the trans in short
order (due to the extra torque)...best pricing seems to be Summit or
Jegs...approx $1500 for manifold...runners...and TB...still need $700 + for GM
sensors and ECM...chip and harness...fuel pump etc...$2200+ for parts...$3000
from Accel with Accel DFI ECM...and the GM ECM gives Altitude Sensing...Spark
Control...Torque Converter Control...and Limp Home Mode all standard...these
are all extra cost "options" as I understand it for Accel's DFI......what do
you think...is there a better way?

2a) Accel DFI vs GM ECM with proper WOT calibration?

2c) Anyone using the FP Performance ECM with the wide band O2 sensor...for
closed loop at all times including WOT?

3) How about the Electromotive kits?

4) How about the Howell TBI kits with the Holley TB and GM ECM?

5) I don't think that a modified TPI (big manifold...big TB...big runners and ported
plenum) would be able to support a 406ci to 5500 rpm...is this correct?

5a) I also imagine that a modified as above TPI would cost as much as a Super
Ram wouldn't it...and not be as effective?

6) Looking through the archives showed that most weren't happy with the Holley
TBI...or Howell TBI...anybody have success with either of these systems as the
pricing is right?

7) How about the single plane carb manifolds plumbed for MPI from
Holley...Accel...Arizona Speed and Marine etc...anyone having success with these
on the street?

7a) I understand that in a wet/flow manifold design the single plane would lose
torque in the lower rpm ranges (under 4000 rpm or so vs a dual plane)...and
that my conservative cam
timing wouldn't allow the higher rpm needed to really use a single plane
manifold...is this still the case in a converted to MPI single plane manifold
(now dry/flow)...seems like the air velocity and cylinder filling would remain
constant with or without the fuel being introduced?

7b) I know that Arizona Speed and Marine will plumb a high-rise dual plane
manifold for MPI...anybody try such a thing? 

8) Anybody use the Barry Grant VFI TBI?

9) Anyone try the TPIS Mini Ram?

Sorry for the length...looking forward to your replies!

Thanks a lot...Doug