Big, White & Sl

I know it's probably been hashed over a million times so can someone point me to a thread . Daily driver so I still want the gauges and everything to work. Just trying to get a handle on whats involved electronics wise. Search didn't give me the info i need

1983Chimaera

First question that comes to mind is "WHY???"...But all head shaking aside;

What specific electronics are you worried about? If it's an electric choke carb you just have to supply switched 12V to the carb, and otherwise use your existing harness sensor hookups for water temp and oil pressure. You should already have a coil-in-cap HEI, so that part is done. Pretty much all you have to do is leave your TPI harness plugged up as is, just unhook the injectors, cold start, TPS, EGR, knock sensor, and IAC plugs. You can leave the computer in place, it just won't be doing much of anything. It shouldn't be more complicated than that, but if I'm wrong someone please correct me (I went the opposite direction and installed TPI on a previously carb'ed car).

Hope you don't mind if I ask why you are removing the TPI? The earlier ones were dirt simple, and the low end torque and crisp throttle response are far better than any carb setup. I know a lot of people get intimidated by EFI setups, but as electronic systems go TPI is still extremely easy to work on.

1983Chimaera

BTW I'm assuming you're removing the electric fuel pump outright and replacing it with a cam driven mechanical or low pressure electric pump (12 psi).

Big, White & Sl

Ok, I guess I'd better give a little more detail about what I'm asking.

Background: I have an 86 Camaro drag car and I'm toying with the idea of swapping the engine and suspension stuff into the 89 GTA I just bought and building a hot street car. The camaro sits most of the time and I'd rather have something I can use regularly. Engine is a 12.5:1 355 with Brodix Track 1's and all aftermarket internals. My idea was to change the pistons for a more streetable compression and put a big hydraulic roller, built 700R4 with a high stall lockup converter, and the Currie 9" out of the camaro(35 spline axles detroit locker, maybe 3.70 gears it has 4.56 now) and all the suspension stuff. I have access to a bare first manifold, but it'd be alot cheaper to use the carb and everything I have now than to buy injectors, throttle body, MAF, tuning stuff and all the other things that go with EFI.

What I'd really like to know is what will be involved. I still want the gauges, AC and stuff to work.

Oh and as far as fuel pump I was planning on a 255lph with an aeromotive 13208 return regulator. If that won't work I have an A1000 pump sitting on the shelf.

1983Chimaera

Ok, so it's not exactly a "running" TPI right now, or a complete setup. I can understand that, especially if major components (MAF, etc) are missing. I personally still much prefer TPI, I just find that most people throw their hands up at it relatively easy the first time it gives them any issues. Considering the simplicity of the system it's amazing that they do, especially since most of the issues stem from the wiring and components they're troubleshooting being 25+ years old. Electrical gremlins can be a bitch, no doubt, but most assume the entire system is flawed when the problem can be as simple as a bit of cracked insulation on old wiring.

Most of what I said should still hold true. Your TPI wiring harness will have the plugs for coolant temp, tach, voltage, and oil pressure, and are independent from the ECM. The ECM did get an input from the coolant temp, but there are two sensors for this. You just need the one for the gauge to remain. You can delete pretty much everything else. Make sure the fuel pump is wired with the correct size fuse to protect the circuit, if you have it on a pressure regulated system with a return line to the tank it should be constant on I believe (again, different from my setup, someone else chime in). The A/C system wiring should stay exactly as it is, that's independent of the ECM and engine harness. Depending what you run for spark you can either leave the stock HEI in place with it's wiring, or run whatever aftermarket setup you prefer using their instructions. I'm running a modified HEI that only has the pick up coil still in it, an external remote mounted coil (to keep it cool) and a Mallory Hyfire 6A digital CD box in place of the ignition module. I got tired of the HEI cooking its modules, and the Mallory was already on hand and far more precise anyway. Even wiring that in was dirt simple.

If you really want to keep the gremlins to a minimum and save your self headaches down the road, get yourself a bunch of various colors of wire (12-18 gauge) and build a new harness. You don't have a lot to wire up in your setup, and knowing the wires aren't corroded, burnt, broken, or shorting somewhere will save you much grief (and possibly late nights stuck on the side of the road!). It will also let you run the harness however you like, including being able to hide it in fenders and keep the engine compartment much tidier, always a plus on a built car. Always use weatherproof connectors, heat shrink tubing over connections/splices, and test each wire for good continuity. A bulletproof electrical system is the core of any decent build, as a bad one makes it nearly impossible to tune.

If you ever do decide to go TPI again, look into Megasquirt. An MS-1 is all that's needed to run TPI, has a built in MAP sensor so no MAF to worry about, runs with HEI spark and can be upgraded later to computer controlled spark, and has a pretty easy learning curve. It's also cheap. I've been running MS-1 for 5 years no with no issues, and the ability to retune my car myself anytime has always been a huge plus. It only uses 5 sensor inputs, one of which is the aforementioned built-in MAP. The other 4 are coolant temp, TPS, tach, intake air temp, and O2. If you use a wideband O2 and controller it will also self-tune, all you have to supply is a starting point fuel table for it to work from, and it has a built in generator for that (plus tons of help on forums from lots of friendly people). Doesn't get much easier than that. It's certainly easier and cheaper than messing with PROMs, custom chips, or spending big bucks on things like Holley Commander.

Big, White & Sl

I actually thought about using the megasquirt and the First manifold. The TPI is complete right now. Here's the thing, the motor makes about 450-470hp at the crank and going EFI means all the above mentioned things. Where as, All I have to change to put the carb motor in( aside from lowering compression and hyd roller cam which would be done either way) is swap my victor junior with the built in 1" spacer for a standard victor jr and a cowl hood. big difference in cost

1983Chimaera

Not really. Cowl hood is going to run you $400-500, plus a decent carb is going to be several hundred. Both of those can be lowered with using swap meet/used items, but prices vary widely as does quality. To get that power range out of a TPI system is going to take modifications as well however, or maybe switch to a different setup from one of the many aftermarket available. Again, savings can be had by finding used parts, just beware of condition/quality. My TPI was a complete 1985 Corvette unit from Ebay for $400 back in '07, ended up ditching the Corvette 4-bit ECM for MS-1, replaced the Rochester injectors with 28lb-hr Bonneville SSE ones, ported/polished/port matched the intake and polished the upper plenum and runners to mirror finish, deleted the cold start and had the fuel rail TIG welded to remove the fuel feed to it, removed and blocked off the EGR, and made a block off plate for the IAC (MS-1 doesn't support it). Later I added a throttle body airfoil I got for free. I built mine for daily driving, good bottom end and midrange torque, and throttle response with excellent driveability. On the flip side I have a '94 Mustang with a 5.0L that I carb'ed. The Mustang behaves excellently, gets 18mpg in town and 24 mpg on the highway, makes over 400 hp, and purrs every time I start it up. The difference between the two is I never have to mess with the TPI tune unless I alter something in the engine. The Mustang has to have the carb tweaked now and then, usually with major changes in weather, or if I'm driving long distance (elevation changes).

Big, White & Sl

I already have a carb and I'm gonna make my own cowl hood. The First TPI manifold will support the hp but there's alot of other things to make it work. The motor in the camaro is complete, just need to change the pistons to bring the compression down.

IROCZ28HAYES

It sounds like I need to pick your brain before I do the TPI swap to carb

1983Chimaera

I really think most people get frustrated with TPI because they overlook a major (and easy to fix) problem, usually throwing money at replacement parts while ignoring the most important; the wiring harness. The wiring in any car is generally taken for granted, and when problems rear up everyone starts buying new components until they get fed up and rip out a perfectly good system. Corroded/broken/shorted/melted wiring that is 30+ years old can easily cause headaches, yet it's easily overlooked. Building a new harness is relatively easy, or one can be ordered from Painless or a few other sources. I've heard a TBI harness can also be used (just add 6 more injector plugs). It's just a shame to see a TPI car reduced to carburetion solely because the owner "couldn't get the TPI to run".