1970 GMC putting in 89 Vett TPI

[Roger 555]

I have just started the wiring and have lots of questions. Planning on using the vett harness and my 1970 truck harness combined. Has anyone done this type of install

[Bigdav160]

I had a '72 with a TPI
My '73 Z28 is TPI

There's several others on this board with TPI's. Post up your questions.

I found there is very little wiring to integrate. I also ran minimal sensors- TPS, MAP, Coolant, RPM. No o2. It ran fine in open loop.

That Corvette had VATS, I believe. There are work arounds for that.

[MARKDTN]

Following is information on TPI swap in a 68-82 Corvette, however much of it is applicable to a 67-72 truck. The big difference is the fuel tank. If you don't mind the tank behind the seat, you can use a stock tank and the Ford external pump. The truck I did was a short bed and he wanted the tank out of the cab. I looked into a 87 truck TBI tank and I think it had clearance issues with the rear suspension (might work on a long bed). I used an '86 S10 Blazer tank from a 2.8TBI vehicle. I even used the fuel lines from this Blazer up to the engine compartment with some re-bending, but they worked pretty well. This put the filler rear and right. He swapped to a stepside bed from a 88-99 pickup and had the body shop swap the filler around. It did require a bit of frame cutting and boxing, but it was all behind the axle mounts. I just swapped the TBI pump to a TPI pump from an IROC Camaro. The TBI tanks work nicely because they use barbs on the hose insead of screwed firttings. Be sure to swap to FI hose and FI clamps, there is a difference and it is important. On the truck, he wanted headers. I despise headers, on my own truck I would use stock manifolds and weld a bung into the exhaust for the oxygen sensor. I mounted the ECM behind the glove box which took up a lot of room. If I ever did another, I would buy a C4 Corvette weatherproof ECM and mount it in the engine compartment instead so it sounds like you are on the right track there. That requires a more expensive harness and ECM (if you didn't already have them), but it will help in the cab. On the swap I did, I used C4 Corvette serpentine accessories, which forces you into electric fans because the aluminum water pump cannot stand up to mounting a fan. If you go this route and have A/C, it will require a custom hose. Also, you will want to upgrade to a CS144 alternator, the CS130 is not very reliable. If you don't want electric fans, an alternative is 88-95 TBI truck acessories, which would allow a pump mounted fan. If you have any other questions, please ask. This was written almost 10 years ago, so finding good used low-mileage TPI engines is probably not possible now, and the prices are not correct anymore. Also you have already made some of the decisions about masss air vs: speed density. Just look at the technical info below and ignore those details. I have included some of that so anyone looking later will have all the facts.
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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. I have been told that you can also use a 3.1 Corsica or Cavailier harness with a little work, it uses the same 7730 Speed-Density ECM. 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 or non-overdrive-automatic transmission I 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 Airtech (also available at O'Reileys). If you have a 78-82 you can use your fuel tank with an 82 sending unit and a TPI pump. 68-77 can also use a modified tank or Rock Valley makes a tank for these cars with a baffle and a GM internal fuel pump. Stock 82 tanks do not have a baffle contrary to popular belief. 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. I recommend using VSS to get better drivability. 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 complete engines 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. Corvette fuel rails fit F-body intakes and vise-versa. 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 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 and pre-LT1 B-body. The F-body intake gets it's exhaust for EGR from the center passages in the heads like most SB Chevys. A Corvette intake gets it's EGR exhaust from the RH exhaust manifold/header through a flex-tube to an opening near the distributor-no center passages in the intake. If you are required to keep EGR and you have a Corvette intake, I recommend getting the C4 exhaust manifolds. They are like mini-headers, and have a 2 1/2" outlet. I have them on my 69 and like them.

As far as a throttle cable to use, on my Vette, I used a TPI Corvette cable, 1990 I think (now discontinued from GM) but you have to cut the end off inside the car and use a hood-release-cable end (Corvette Central 342138 "cable stop") to get it the correct cable length (the housing is OK). You must use a cable from the type car your throttle body came from if you want to have a chance of not cutting it. Again, 85-88 use a straight pull, while 89-92 have a circular attachment for more smooth actuation and so the inner cable is longer. On my 83 truck I used a TPI F-Body cable and it was OK, but I had to coil it up into a loop in the engine compartment because the housing was so long. I also TPI'd a 72 Chevy truck and used a 90 350 TBI truck cable for it. It was 1/2" short outside if anything, but I was pretty pleased with it all told-I didn't have to shorten it. In a Vette it might be about right. In all vehicles I've done you need a die grinder to square the firewall hole off a bit. All vehicles I've done used the late throttle-body.

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 also www.jagsthatrun.com for misc hard to find conversion parts and info.

[Roger 555]

Originally Posted by Roger 555

I have just started the wiring and have lots of questions. Planning on using the vett harness and my 1970 truck harness combined. Has anyone done this type of install

My 89 vett engine did not come with a air pump I don't need it for western Colorado where can I find an adapter pulley so that I can stay with the same belt?

[Roger 555]

Originally Posted by Roger 555

I have just started the wiring and have lots of questions. Planning on using the vett harness and my 1970 truck harness combined. Has anyone done this type of install

My 89 vett engine did not come with a air pump I don't need it for western Colorado where can I find an adapter pulley so that I can stay with the same belt?

[Longhorn 70]

could you also use the ECU and wiring from a 90-91 instead? They are supposed to be easier to set up and more reliable than 89s.

As far as the air pump, I have seen them on eBay reasonably priced. or THIS