TPI Swapper's guide: Part I, shopping for TPI parts
Swapping a TPI into a car that didn't come with one, can be overwhelming. It can be even harder, if you don't shop smart. There are many parts and accessories out there for TPI, and many used setups for sale. In this installment, I will focus on the used setups, and the parts needed to operate them. Used TPIs are fairly cheap as many people are converting to carb, or upgrading to other forms of Fuel Injection. You can often find a good deal on a decent used TPI setup from just the intakes and runners, to the whole nine yards including the wiring harness, sensors, distributer, ECM, and then some fall in between. I am writing this to help others avoid some of the pitfalls that exist (mostly ones I have encountered). The more you plan before you shop, the easier the swap will be.
Here is an example of what is for sale on eBay. Here are some highlights:
90° fuel lines off the fuel rail. Notice they point towards the drivers side of the assembly. This denotes that the setup came off of an F-body. If they were straight out, then it came off of a Corvette. This is very important if you want to use factory fuel lines.
The assembly comes with the Throttle cable bracket. Although they are cheap new from the Dealer, every little bit counts, and thats $10 you can spend on something else.
This unit was equipped on a car WITHOUT the Cold Start Valve. This is important depending on what you are installing it on. If you are using an '89 or later PROM or wiring harness, you won't be using a Cold Start Valve. If you do get one that came with the valve, and don't want to use it, you can get plugs for the hole in the runner and a cap for the fuel rail.
Here is another auction. This setup has some pitfalls, none to serious.
Notice this unit was equipped with the cold start valve. No big deal, the plug and cap cost $20.
There are large dents in the runners. Not only is this unattractive, but can obstruct airflow, and we all know that costs horsepower.
Some of the bolts are missing. This is no big deal, but can be a hassle, its another thing you will have to buy later. The more complete it is, the better.
Here is a checklist of things you will need. The more the "package" includes, the less you have to shop around:
Usually, the "package" includes what you see in the pictures above, the upper and lower intakes, runners, fuel rail w/ injectors and the throttle body. Prices usually start around $300 for just that. The more thats included, the higher the price. Many people who have totally gutted the car, will sell the harness, ECM, distributer also, and prices for this are usually $600+
I will try to go into some of the "checklist items" in detail, so you know what you are looking at, and what to look out for.
TPI Upper intake, lower intake, runners:
1985-1988 had provisions for a cold start valve. If you are going to use these, you will either need to use a chip for '86-'88 systems, or use a newer ECM/chip combo, and block off cold start system. A fuel rail cap and CS valve plug is available to do so.
1989 was delete of the cold start valve, so the upper intake (plenum), runners, and lower intake do not have provisions for the valve.
1990-1992 was also delete the CS valve, but also had provisions on the Plenum for a MAP sensor bracket above the vacuum nipples on the rear of the Plenum, since '90-'92 was speed density controlled. If you want to use a TPI off of a Corvette, be carefull, the lower intake was made to bolt up to cylinder heads that do not have EGR passages, so you won't be able to use a Corvette intake, unless you want to delete the EGR.
Starting in 1987, the angle of the four center bolts of the intake changed, so if you wan't to use a pre-87 intake on an '87 or later engine (or vice versa) you will have to modify the four center holes to make it bolt up properly.
Throttle body The throttle linkage supposedly changed in '89 so you will need to order a throttle cable for whatever year throttle body is on the car.
Fuel Rail The fuel rails are essentially the same between the years, the major difference is the F-body (camaro, firebird) fuel rails, vs the Y-body (Corvette) fuel rails. They are distinctly different, and will impact how you run your fuel lines. The Fbody rails have a 90° bend towards the drivers side for the "intermediate" fuel lines to hook up to, before going into the flex lines. You will need the Fbody rails if you want to use factory lines. The Ybody fuel rails come straight out, and will need custom fuel lines made to work.
Here is an example of Custom fuel lines made to adapt a Corvette style Fuel Rail, to an F-body. You want to make sure you have clearance between the alternator and bracket if you are retaining the V-belts.
Injectors You will need to know what size injectors come w/ the TPI, or at least know the engine size they were on.
19lb/hr injectors were used on 305s,
22lb/hr injectors were used on 350s.
All the Y-body units should come w/ 22lb/hr injectors, since the Vette didn't come w/ 305s, and all '85 and '86 F-body units should come w/ 19s since the 350 wasn't used on these cars untill '87 unless it was retrofitted.
1985-1989 systems used a Mass Air Flow (MAF) sensor.
1990-1992 used a Manifold Absolute Pressure (MAP) sensor. Due to the unreliability of the MAF sensor, speed density systems (MAP sensor) are more desireable, and easier to install.
NOTE: 1985 MAF systems used a MAF Burnoff module in conjuntion w/ the ECM and were very unreliable, and should be avoided.
Distributer More than likely, you can re-use your stock distributer, providing the one that is currently installed IS NOT a vacuum advance distributer. You can either use the large "coil-in-cap" or the small style, you will just have to wire accordingly.
Wiring Harness You WILL need a wiring harness to operate the TPI system. A TBI harness can be modified to operate a TPI, but if you are converting from carb, or don't want to mess w/ converting the TBI harness, you will need to get a TPI harness. If you are using a MAF system w/ a cold start valve, you will need the harness for that. If you are using MAF w/o the cold start, you can use the same harness, and just leave the CS valve connector unplugged. If you are using speed density, you will need a speed density harness. NOTE: 1985 used a MAF burnoff module, and these harnesses should be avoided.
Many after market companies make wiring harnesses for TPI. Painless Wiring has impecable quality, but ARE NOT MEANT TO BE USED AS A STOCK REPLACEMENT. If you want to use a Painless Wiring harness, you will need to drill a hole in the firewall to run the wires, or cut the harness in half, and solder in the needed amount so it will be long enough to be run through the factory pass-thru behind the passenger side fender. *update: Painless now makes longer harnesses, but they are still not original replacements.
CTS/IAT sensors Except for V6 Camaro's the Coolant Temp Sensor (CTS) and Intake Air Temp (IAT) sensor are the same Part Number. Since they are relativly cheap, and big problems can arise if bad, I reccomend new ones with the swap.
Knock Sensor The knock sensors are different between 305s and 350s, and also different between MAF systems, and Speed Density (primarily becuase the MAF has an external ESC module, and the SD is internal to the ECM.) So purchase accordingly. I reccomend a new one.
ECM This is an important decision. If you want or are using a MAF system, you will need the 16198259 (165) ECM. If you are using Speed Density, you will need the 16198262 (730) ECM. The Speed Density systems use a MAP sensor, and are very reliable, and cheaper to fix (comparison of replacing a MAP sensor vs. a MAF sensor.)
PROM/MEMCAL Which PROM you use will depend on alot of things. If you are keeping the cold start valve or not, if you are using MAF or Speed Density, if you are putting it on a 305, 350, or other engine, if you have manual or auto trans, etc... If you are keeping the CS valve, you will need a PROM for '86-'88 vehicles. If you are not using a CS valve but keeping MAF, you wil need one from an '89. If you are using Speed Density, you will need '90-'92. Also note that if you are using an '89 or later chip, you will need to address the VATS/PassKey issue. It is very easy to "disable" the VATS feature w/ a custom chip. Your car WILL NOT START w/ an '89 or later chip and you do not have VATS. You can either send the chip out and have it "disabled", or you can retrofit PassKey into the vehicle. Also note that Corvette PROMs and F-body PROMs cannot be interchanged.
Fuel Pump/Fuel Sender The decision to install an in-tank pump vs an inline pump is highly debated much like the MAF vs Speed Density debate. If you are going to use an inline pump, you will not need to mess w/ pulling the fuel tank. I have heard several people having much luck w/ their inline pump sucking enough fuel through the stock sending unit, even if a TBI pump is still hooked up. You will need high pressure fuel lines from the pump to the fuel rail. If you install an in-tank pump, the TBI guys have an advantage, the TBI fuel sender has the high pressure fitting on the sender, the Carb fuel sender does not, and should be replaced w/ a fuel injection sending unit. Many pumps are available for in-tank use, such as stock pumps and Walboro pumps.
High Pressure Fuel Lines Since TPI fuel pressures can reach up to 45psi, and w/ an Adjustable Fuel Pressure Regulator (AFPR), they can reach 50+, you NEED fuel lines that can handle the pressure. One easy, reliable, and affordable alternative is to buy used fuel lines from a salvage yard. TBI, TPI, and Fuel injected V6 F-bodies all use the same fuel lines, so lines from any of those cars will work. You can usually get the entire lenght of line, fuel filter bracket and both rubber flex lines for less than $30. If you are converting from TBI to TPI, you already have these lines. If you are converting from Carb, you need these lines. You can also run other forms of High Pressure Fuel line from the tank(or pump) to the fuel rail, as long as they meet pressure specifications. Many companies like Summit sell AN-"O-ring flare" adapters, so you can use AN fittings, and screw them into the fuel rail.
Fuel Pump Relay You will definatly need one of these, and how you hook it up depends on what wiring you will use for the TPI. It is reccomended you use a new one.
Relays(other) If you are using a MAF system, you will also need a MAF Power Relay and the MAF Burnoff Relay on top of the Fuel Pump Relay. Your wiring harness should have provisions for this.
Air Intake This is a simple, yet always confusing topic. You will need to plumb clean air into the throttle body but there are many ways to do it. First off, the Carb guys are cursed w/ a passenger side mounted battery. Since the battery is on the drivers side for TPI, most of your "Cold Air" kits are routed to the passenger side of the radiator. You can either look around for a kit that routes to the drivers side, or you can relocate the battery. You can also make a custom cold air.
Here is a custom cold air setup using 3" exhaust pipe painted black w/ a 45 degree bend, a 3" cone filter on the end, black plastic to seal off the filter from the engine bay, and a snorkel from a TPI firebird turned up-sidesown (so it points to the drivers side). This is easy to do, works great, and cost less than $50. This is installed on an '87 LG4 converted to TPI.
A throttle body mounted cone filter should be avioded at all costs. They suck hot air directly from the radiator, wich can reach 200+ degrees. Testing has proven around a two tenths gain w/ a throttle body mounted filter vs a cold air induction.
Also note that a Camaro's "dual snorkel/filter" air intake WILL NOT fit on a firebird. The front support is different (excessive cutting required), it will not fit between the turn signal housings, and will also not clear the hood where it goes over the radiator.
Misc. Other notes: Except for the differences in Intake Manifold center bolt angles (which can easily be fixed) all other mechanical aspects of the engine can be re-used w/ the TPI setup, such as Heads, Camshaft, block, etc.... When the intake is off, its the ideal time to replace the camshaft and such, but it is not required. The stock components will work.
You will also need to purchase the gasket set for the TPI. Lower intake gaskets should be the same for the Carb/TBI engines, but you can usually get the lower gaskets in a kit w/ the runner gaskets. You will need Lower, runner, and throttle body gaskets.
***If you find any inaccuracies, or have anything to add, please email ADMIN.***
Special thanks to Jim (aka Jim85IROC) for contributing.