350 Chev to 400 Small Block

[Shannen Durphey]

David Sagers wrote:
> 
> Looking for someone with experience modifying and setting up a TBI fuel injection system.
> I am replacing the tired 350 engine in my ¡92 Suburban w/TBI.  Instead of going back to the stock 350, I want to install a small block 400. I¢ll also add a few extras like better flowing heads, a mild cam, headers and a free flowing cat and exhaust system.
> 
> This combination will require more fuel than the stock combination. Small block 400 have been around for many years and I¢m sure someone has done all this before, and since I don¢t want to re-invent the wheel, I¢m looking for information about how to feed this engine and how to get the fuel mixture correct so its not running rich or lean.
> 

The conservative guy will stay with a cam recommended for computer
controlled vehicles, or at least within the chip maker's recommended
limits.  I'v found a good cam for pickups (carb'ed or EFI) is GM perf.
parts 12353914 (a Crane Compucam). You can see it here:
http://www.gmgoodwrench.com/parts/pdf/066-071.pdf
and here:
http://www.cranecams.com/master/apps/chevy5.htm#1. CompuCam
cam #2010

> Some of the options available are 1) Turbo City offers high flow throttle bodies, high flow injectors and computer interfaces to make the speed density system work with a cam that has longer duration than a stock cam.  Do I just add all their high flow stuff and hope it's close?
> 
> 2) Edelbrock sells a complete, tunable TPI system to replace the factory TBI, cost is $1200.

Edelbrock sells two systems.  A tunable system never intended to
replace factory TBI, and a manifold/injectors/chip setup to replace
factory TBI.  Edelbrock makes the chip for this setup, and they base
it on your selection of parts from their catalogue.  There may be less
to the chip than it seems in terms of changes.
> 
> 3) Several companies offer computers that intercept the computer signal and modify the fuel and timing curve according to adjustable settings.
> 
> Finally, 4) New chips for the factory computer are available from after market performance companies to compensate for the bigger engine.
So are adjustable fuel pressure regulators.

There are mechanical differences, too.  You'll need a set of late
heads drilled out for the 400 if you intend to run a factory manifold.
> 
> Anyone out there been through this before? What works and what doesn¢t? Thanks in advance.

If you want to put your vehicle together and drive it, stay
conservative.  Radical changes, big cams, lots of "high perf" parts
require spending time getting things right.  Many people would rather
"plug-n-play".  Decide now what your level of commitment is.

Shannen