DIY: TPI conversion
 

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:

http://i272.photobucket.com/albums/j...y/102_0783.jpg

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.

http://i272.photobucket.com/albums/j...y/100_0806.jpg

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:

http://i272.photobucket.com/albums/j...y/102_0715.jpg

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.

Re: DIY: TPI conversion
 

Shweet. I'm doing this to my k5

Re: DIY: TPI conversion
 

A Camaro throttle cable and tvcable for the 700r work perfectly on our trucks.

Re: DIY: TPI conversion
 

Im in the middle of doing this swap. My only advise is make sure you know if you have the 305 or 350. The 305 tune and injectors are different from the 350.

Re: DIY: TPI conversion
 

Nice, good to know. Altho, the Camaro cable appears to be discontinued thru aftermarket suppliers now. Which brings up a good point, when hunting down a TPI intake for a conversion, try to get one that is complete as possible. TPI manifolds have alot of specific pieces and if you have to buy missing things, it adds up. The manifold I used was a $50 CL find, but was missing little things like the bolts, throttle cable bracket, TPS, T-stat neck. Ended up costing me another $50-60 bucks buying the little pieces to make it complete.

Yes, there is quite a difference. For stock or mildly modified engines, stick with the stock injector sizes.

305 use 19 lb/hr injectors
350 use 22 lb/hr injectors

You can recondition used injectors like I did, however for peace of mind ebay is a good source of new injectors. Many of them are F@rd take off and new ones, same style injector as stock TPI ones tho.

The tune can be a complicated aspect of this swap. If you are converting the stock truck or a built up engine, you're going to have to tune it, no question.

Re: DIY: TPI conversion
 

If you go with the MAF setup it can handle some engine modifications with the stock tune. The SD system will not.

Re: DIY: TPI conversion
 

:metal:Congratulations, this is good work.:metal:

Re: DIY: TPI conversion
 

Also the some of the sensors between a 305 and 350 are diff. I know one for sure is the knock sensor.

Re: DIY: TPI conversion
 

Good write up. Imo the only way to go is OBD2 with the 411. More control over things, easier to tune an you can control a 4l60e/80e with it to. Eventually that's how mine will be once i get all the parts i need...

Re: DIY: TPI conversion
 

I agree..If your starting from scratch the 411 is the way to go..I got all my setup from a donor vehicle which provided everything. I did take the lazy route and go with a wire harness from fuelinjectionconnection. Someday I will upgrade to the 411, but for now I am enjoying all the benefits of fuel injection at a pretty reasonable price.

Re: DIY: TPI conversion
 

Thanks, I see the TPI question come up on the boards ever once in a while so I wanted to post the answers for everyone to see.

The knock sensor is really the only different one, as they are tuned to the frequency of specific displacements to pickup knock.

I also agree, I was not aware of the OBD2 swap when I first installed the TPI. Many pieces like the V8 prom and the ECM terminals are slowly being phased out, and soon will be unavailable new. The fact of donor cars being crushed all the time means it's tough to find V8 stuff. I had to modify a V6 prom to use in my 1227730 ECM, also salvaged from a FWD V6 car.

In contrast, the support is huge for the flash LS1 style PCM's.

Rich, how do you like you fuelinjectionconnection harness? I always wondered about their quality.

Re: DIY: TPI conversion
 

Very happy with the harness...Would like to know if he would make one for the 411..

Re: DIY: TPI conversion
 

Im using a factory vortec 5.7 truck harness for mine. A connector swap an repin is all thats needed to use the harness with the 411 pcm. Then you make it stand alone an add in the injector plugs and reroute some of the sensor wiring. The guy doing mine is suppose to make a write up about how to do it all. I'll link it when he does, it might be a bit since im not sending him the stuff until after the holidays...

Re: DIY: TPI conversion
 

I have used Robert on a few harnesses now also. They are nice pieces, and reasonably priced too.

Re: DIY: TPI conversion
 

Awesome, since many of us TPI swappers are on a budget, it's good to know there is a reliable, affordable alternative out there besides the overpriced painless wiring stuff.

Re: DIY: TPI conversion
 

Yeah, I know. I have used the TBI, LT1, and LS harnesses. All nice pieces, and new connectors. No brittle, 20+ year old stuff. That helps when you are ham fisted like me.

Re: DIY: TPI conversion
 

I'll be doing my swap as soon as I get my other motor out the car... I have a tpi out a 89 corvette, painless harness, powder coated pulleys... Also toying the idea of turbos

Re: DIY: TPI conversion
 

Any other TPI swappers out there? I'm getting mine dialed in and it's alot of fun.

Re: DIY: TPI conversion
 

I'm thinking about doing the TPI to my 74 SWB 4wd. It has no engine transmission/t-case in it right now, but I have a th350/203 and a 350 engine for it. I have a tuneport for it and priced the harness and custom programmed computer at $400. My buddy has one in a 72 and loves it.

Re: DIY: TPI conversion
 

Yes, I installed a TPI on a 75 Chevrolet car. It works great.

Re: DIY: TPI conversion
 

I never swapped a TPI, but I did tune my '86 Trans Am quite a bit. I made 75 horsepower and same TQ with a Summit Racing (1103) cam swap and a tune on a 305!!! It didn't even have headers!!! I used the Moates adapter with GMECMEdit I think it was called. Very easy to tune it. Pulled 27 MPG with the 700R4 and 3.08 gears with a heavy foot. Even accounting for the brick-ness of our squares, I would think low 20's would be easily possible even for 350's.

Re: DIY: TPI conversion
 

I have a 1989 K1500 which has graduated from TBI to Eddy's MPFI conversion (that actually was pretty good, but I didn't have a clue about tuning at the time and they weren't kidding about stock vortec crate application). Running Rbob's EBL right now with speed density TPI, having a 383 built and installed EFI connections 24x reluctor on my way to collecting parts for a 411 conversion and ditching the dizzy.