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1989 Chevy K2500 TBI Setup - What's Your Problem?

One of the easiest ways to increase fuel flow is with an adjustable fuel pressure regulator. Companies such as JET, Turbo City, and CFM Technologies sell adjustable pressure regulators. The price hovers around $90 depending on the source. The approach is to first measure the existing fuel pressure. If the pump in your truck is already delivering 13 psi at the TBI, consider yourself lucky and don't bother with the adjustable piece. More likely, the fuel pressure will read 10 to 11 psi. Mount the new regulator and bump the pressure to 13 psi. You won't be able to go much higher because stock pumps generally can't generate more than 14 or 15 psi. Keep in mind that raising the fuel pressure increases fuel delivery across the entire engine operating range. At part-throttle, this additional fuel isn't needed, but the oxygen sensor should sense a rich mixture and reduce the injector on time (pulse width), which will lean the mixture back to the ideal 14.7:1 air/fuel ratio. At wide-open throttle, the computer switches to its base fuel map and the additional fuel pressure will increase fuel flow and (assuming the engine needs the additional fuel) will increase power. You should test any fuel pressure change with a WOT acceleration run in Second gear from about 30 to 60 mph. If the truck accelerates to 60 in less time, the engine is making more power.

Another simple trick we've tested that works well is the PowerCharger, (we call it the soup bowl) from Hypertech. This is a simple radius adapter shaped like a bowl and placed between the truck air cleaner and throttle body. Summit sells these adapters for $37.25 (PN 4001). We tested the PowerCharger on our TBI 350-powered Jake truck buildup ("Project Jake, Part II," July '04) and discovered it was worth 8 lb-ft and 8 hp. If you want more, multiple companies make swirl-inducing TBI spacer plates. CFM Tech-nologies, Trans-Dapt, AirAid, JET, and many others manufacture spacers that, while we've never actually tested them, appear to be worth some torque. Expect to pay anywhere from $50 to $100 for one of these spacers.

You also mentioned camshaft requirements. The stock camshaft for your application is pretty mild. We found the specs for an '81 to '87 computer-controlled flat-tappet hydraulic cam that specs out at 194/202 degrees at 0.050 with 0.384/ 0.403-inch lift. Adding a longer-duration camshaft with more lift will drastically improve airflow and increase power at a higher engine speed. The problem is that it will require additional fuel that will mean changes to the base fuel map in the computer. We'll get to that in a moment. If reprogramming the computer isn't a deterrent, consider a cam like the Edelbrock Performer-Plus flat-tappet hydraulic camshaft and lifter package (PN 3702, $127.95, Summit Racing). This cam is designed specifically for the TBI 350 small-block and specs at 194/214 degrees of duration at 0.050-inch tappet lift with 0.398/0.442-inch lift. As you can tell, it doesn't deliver much of an increase in lift. The advantage is the additional duration that will move up the power curve slightly. The downside to this cam is that for a tow vehicle, it may hurt the low-speed torque slightly, which might not be a bad thing. The idle quality should still be close to stock.

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