I have a 350ci with a Q-jet, i would like to install a injection!
what about fuel economy? poor?

I will probably take a Performer RPM Pro-Flo® EFI System, is it a good idea?

ABSOLUTELY! Mileage? Better! Power? Better!
Fuel injection is definitely better. Going with a perormance FI system you probably won't see too much gains in economy, but you'll see gains in performance. Good luck with the switch!

This is written with TPI in mind. Unless you plan to do major high-perfortmance revisions, TPI is an ideal setup. Parts are easy to find, and it is pretty mu8ch bulletproof. You should see a mileage increase as well. In my truck mentioned below, I went from 14 city to about 17 city mpg.

You have a unit
First you have to determine whether you want mass air flow or speed density. The C3 is more conducive to speed-density due to space issues. Mass-air flow is easier to make engine changes without PROM changes. If you are technically proficient enough to make a Camaro harness work they can be bought for $100 or less. Aftermarket harnesses range from about $300 for Painless to $500 for Howell to $700 for Street and Performance. Howell makes a great harness, but for a Tuned Port they do not make one that will control the converter lockup on a 200R4/700R4/4L60 transmission. If you are running a manual trans or non-overdrive I would highly recommend them. I have heard great things about Street and Performance harness, but do not have first hand experience with them. I also have a Fuel Injection Specialties (FIS) harness and it is OK. The ECM can be had used for $10-50. A good external fuel pump will cost at least $100. I use an 88 Ford Truck external pump, $114 from CarQuest, made in Texas by Airtex. If you have a 78-82 you can use your fuel tank with an 82 sending unit and a TPI pump. An aftermarket PROM with VATS and Emissions codes removed will be $100-200 depending on source and complexity. You will have to add an oxygen sensor to your exhaust, $20 for the sensor, $5 for the weld-in bung, and say $25 for an exhaust shop to weld it in if you can’t. Some harnesses use VSS and some do not. An auxiliary VSS sensor is around $75. To install a TPI I say figure at least $800 plus the TPI unit and whatever repairs are necessary to bring it up to useable status. I have TPI/700R4 in my 69 Corvette (Howell harness) and an 83 Pickup (FIS harness) and I love it. Starts good, great torque, good fuel mileage, easy to swap onto stock engines (although both of mine are out of 90/91 ‘Vettes).

Differences in years
All Corvette TPI intake manifolds work with the older (through 86) iron heads and the factory aluminum heads through 91. F-body TPI intakes use the upright center bolts on 87-92 and thus fit all 87-95 iron heads (non LT1). Either can be swapped to fit the other with some drilling. F-body has the fuel lines come out on the drivers side and has a central port for EGR. Corvette has fuel lines that come out on the passenger side and has an external port for EGR. The runners are all the same through the years, but the LH runner has a hole for a 9th injector in the 85-88 runners. This can be plugged off if you get a nice LH runner and don’t want the 9th injector or decide to run speed-density. The plenums all physically interchange, but 90-92 have an extra vacuum port for the MAP sensor used with the speed-density computers and wiring. 89 is an odd year, it is mass-air flow but without the 9th injector. 89 up throttle bodies can be used on all years, but a 85-88 throttle body requires a ½” hole be drilled in the front of a 89-92 Plenum for idle air. 89-92 Throttle bodies have a bit more desirable cable attachment. The cable attaches around a circular linkage which has a smoother actuation than the straight linkage on the 85-88. The Corvettes have an aluminum plenum extension over the distributor, the F-body extensions are plastic. The Corvettes use an HEI coil-in-cap distributor for 85-91 (Delco 1103680). 85-86 F-body also used a big-cap distributor. 87-92 F-Body used a small cap distributor with an external coil (Delco 1103479). This same distributor is used in the 87-95 5.0/5.7/7.4 TBI injected trucks.

Why to get it
If all you want is around 300 hp there is no reason to spend a pile of money on a crate motor. The basic $1200 4-bolt Goodwrench 350 with an aluminum intake and a Holley will put out power in that neighborhood. Chevy High Performance (I think) did a series of articles with one of those a few years back and with decent exhaust should get you in that range.

I would look into a TPI. They start immediately in winter, have great vacuum, and will get great mileage. I can open the headlights and the wiper door at the same time with no hesitation at all-solid wooomp. With 3.70 gears (and a 700R4 overdrive) I get 18mpg city and 22+ highway. With 3.55 or 3.36 it would be even better. You can probably find a used Corvette TPI engine for $1000 and with an $800 harness/computer/fuel pump you would be set. On a 78-82 you can use the stock fuel tank with an 82 sending unit and TPI pump and be in better shape than 68-77 with an external pump. With the Vette TPI you would have aluminum heads that would remove weight. Even with an F-body iron-head TPI 350 it will be less weight than a stock intake. It will bolt up to everything in your car, use stock accessories, use your transmission, and the visual appeal is awesome. Don't be afraid of fuel injection, it really works.

As far as websites see:
www.corvettefaq.com for conversions or more TPI info at www.fuelinjection.com

No way I can add to that. Excellent post.

Ken Styer

...and with TPI the bottom end torque will feel like you swapped your small block for a big block!