Originally Posted by oldbogie
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.
ive never messed with tbi much, hence why my other truck has a tpi swap on it . vortec head swap would be nice but do they mayke a votec tbi manifold ? or do i have to get a carb manifold and run the adapter?
im going to pull a valve cover this weekend and check the casting number but im going to assume it has the low compression heads since the truck will run on 85 gas and not ping
how will the vortecs compare to the swirl ports in off idle power and tq ? i do love the amount of power the truck has down low , i am willing to give up some though as if i need to the transmission does have a granny gear to get things moving when towing. ive never had to use it as is though
i should mention the early fall off could be because i am at 6,500 ft above sealevel