DIY: TPI conversion

[MalibuSSwagon]

This is a DIY guide to swapping a TPI into your square. This should apply to all 73-91 squares, this is based on my 86 C10 swap. This is not a complete swap guide, it is intended to provide squarebody specific swap information. I recommend you study the TPI swap guide over at Chevy Thunder and the swap guides/information at thirdgen.org.

TBI truck swappers, your work is cut out for you. It's quite simple to modify the fuel system and harness to convert to TPI. Read on.

Lets start at the bottom.

Fuel system:

Fortunately, GM made fuel injection swap easy for us 73-86 guys. Simply order a 87 model year EFI fuel tank and sender from Rock Auto. Order a 1990 Camaro 5.7L fuel pump, I would recommend an AC Delco EP241. This is the high pressure TPI pump and will drop right into the TBI sender. Fuel lines, the carb feed line is 3/8" and the return is 1/4" There is also a 5/16" charcoal canister line that runs into the engine bay. We need to re-work the system to use the 5/16" for return and 1/4 for your vent line. I was able to use the behind the cab hard lines without modification, however the hard lines running along the frame and into the engine bay are where you have to make some changes. This is my solution and it came out quite well. I found the flexible braided lines and what looked like recently replaced hard lines off a 92 TBI truck in the junkyard. I replaced my fuel lines back to the junction under the passenger rear corner of the cab with these lines, following the factory routing. The TBI lines are a direct fit to the Camaro TPI fuel rail. If you go this route order a 1987 R10 fuel filter as well, they are a $1 for a new filter. Also grab the fuel pump blockoff and hardware from a TBI SB truck if you are converting a carb engine as well.TBI braided lines:



Also, you need to replace all the rubber fuel lines with high pressure fuel injection hose. It's not cheap, I found the best deal was buying the Gates pre-packaged hose. It's around $15 a pack if buying locally, but you get 3ft of hose a pack, enough to do 2 trucks at least. This is not optional, regular fuel hose is rated for 50 PSI, TPI line pressures can exceed 90psi at times.

Accessory drive and cooling system:

I've bundled these together seeing as the water pump is part of the accessory drive. You can re-use your v-belt accessory drive in most cases, and even the mechanical fan on speed density setups. You will need a 85-87 Camaro TPI alternator bracket, you will even be able to re-use your alternator, altho I would recommend an alternator upgrade to at least a 90-100 unit. Otherwise, the rest of your v-belt accessory drive is usable as is. I ran the mechanical fan at first.



If you would like to upgrade to serpentine or already have a TBI serpentine setup; you need a serpentine setup off a car to clear the TPI. You can find this setup on 88-92 Camaros and Firebirds, also Caprices up to 1993 had the same setup. All the V8 F-bodies had this serpentine, TBI and TPI. So it's pretty easy to find.

Cooling system is simple. Get a Dayco # 71203, it's an upper hose for a TPI Camaro, it is cut to fit for the Camaro application which makes it the perfect length for our trucks as is. It will clear either the mechanical fan or electric fan depending on orientation, it's 1.25" on both ends so you can reverse it.

The heater hose to intake is simple, the engineers at GM had their thinking caps on for this one. Provided you hooked up the TB coolant feed, the heater hose connects to the side of the throttle body, I didn't have to cut or re-route the hose. Simple.

Throttle cable:

I used a 1987 S10 2.8 TBI cable, it's a little longer than needed but it has the right ends for the throttle bracket and firewall. It's also available new as ATP Part # Y612. You can see it in the photo above. You could also try a Camaro TPI cable, I didn't have one to try. For you automatic guys, you can use a Camaro TPI kickdown cable. I have a manual trans so I'm not sure what cables would work besides that.

Wiring harness:

There is much debate on this subject about the best route to take. In my mind, the best route would to start with a factory square body TBI harness, you know it's going to fit! Lucky you TBI guys. On the other hand, I chose to make life hard on myself by building a harness starting with this pile:



Which turned out pretty awesome, harness is still working and I learned a ton about reading diagrams, soldering, and patience! haha.

It's simple to modify a TBI harness to run TPI. Look here : Re-pinning TBI to speed density TPI

For everyone who has no desire to cut wires there are many aftermarket suppliers of TPI harnesses. Take a look at the harnesses offered by fuelinjectionconnection.com, they are very reasonably priced and look good.

There is also the LS pcm conversion. Check out TPI OBDII. The LS PCM conversion offers sequential fuel injection, 4L60E/4L80E transmission control, and modern easy to use tuning software. This may be worth it to you guys with built up engines since any dyno shop these days deals with LS engines regularly, and those shops usually won't touch the older OBD1 ECMs.

DynamicEFI is also worth a look if you'd rather stay OBD1 to avoid the huge buy in to OBD2. For less than the cost of EFI live or HP tuners you can buy a Dynamic EFI modified ECM with software.

I believe this covers the square body specific TPI swap details. This was based on my swap, a 1985 TPI intake manifold installed onto a 1986 stock 305 truck engine, converted to speed density. Any questions, please fire away.