Originally Posted by Project89
i just purchased a second silverado 350 tbi with the nv4500 trans ( might be a 3500) i always get it mixed up
my other silverado is the same except it has a tbi to tpi swap on it
im going to use this new truck to tow my twin turbo car to the track in vegas and also out to the salt flats to race instead of just driving the camaro there since either trip is 600+ miles round trip
my first thoughts were to do the tpi swap with the lt1 cam
but i dont wanna really do that , im going to assume the 92 tbi engine has swirl port heads , i havent pulled a valve cover to verify casting number yet
my only gripe with the truck is it falls on its face around 3,200 rpms and thats without towing anything , anything under that its great
im thinking maybe something a lil larger on the cam to shift power up just a lil bit , the bb 454 tbi swap and maybe an edelbrock manifold with th e carb to tbi adapter plate and a set of heeaders
if this was a truck u were going to tow with which way would u go with it
maybe even a cam recomendation
btw gears are out of the question speed limits out here are 80mph on the highway and in the truck i will cruise at 75-80 , while towin id obviously go a lil slower then that
It has swirl port heads it's just a question of whether it's the low compression 191 or the higher compression 193. Aside from chamber volume 76 or 64 cc it's the same head. But 3200 seems a bit early to crap out even for Swirl Ports.
LT1 cam with a chip will help whether you change the heads or not. Headers with duals are another good band-aid with these heads. The big thing Swirl port heads respond to is more cam timing, but the speed density metering measurement system needs 10 inches or more of idle vacuum, preferably more, so this greatly limits duration and timing profile of the cam.
Vortec heads are certainly a decent and popular change and will add about 20-30 hp but require an intake change because of a different bolt pattern from the intake you have. The iron L98 head casting 14101083, in part number 10125377 will fit your current intake, it is the same head as the Swirl Port sans the swirl vane. It was used on the Impala version of the Z-28's L98 engine, a pretty good modern head that's greatly under appreciated.
Your TBI is undersized both in CFM and in fuel delivery for much power. The OEM 350 TBI will flow about 450 CFM, the 454 TBI will flow about 600 CFM and Holley offers a slightly bigger 2 barrel unit at 670 cfm. TBI injectors can be had up to about 90 pounds per hour where the OEM 350 will do about 60 pounds per hour on average. These are based on an 80% duty cycle and about 11 PSI fuel pressure.