Mexacali Express ('72 K10/LQ4/TH350 Retrofit)

[jpstaub]

Even with Delphi's catalog linked in a post above there are a lot of choices to make. Some guidance follows:

1. GT series connectors are the easiest to work with when it comes time to take them apart. Say you put a terminal in the wrong position. With GT series connectors you can generally get the terminal out without much in the way of terminal removal tools other than a jeweler's screwdriver (not that this should solidify a decision since removal tools are pretty cheap). This is due to the tangless design of the terminals for this series.

2. Metri-Pack series connectors are harder to take apart. However, they are the choice for high amperage circuits. They take a terminal removal tool that's relatively common. The terminals are in the auto parts store supply chain. So, if you don't order enough terminals chances are fair that you'll be able to get more terminals without having to wait for a shipment. The same probably can't be said for GT series stuff.

3. Both style terminals require a crimping tool. Item #533 at Waytek is the lowest cost way to go. I've gotten good service out of my tool although if I were doing a lot of harnesses I'd upgrade.

4. Item #422 at Watyek will give you the ability to remove Metri-Pack terminals. I've also used it to work on Series 56 terminals. This one is well worth the money even if you don't play with wiring much. The first time you use it it'll pay for itself.

As far as connectors go relative to the retrofit wiring diagram in a previous post:

Connector A - This one mounts under the dash out of the weather so a sealed connector isn't necessary. Something in a 150 series will do the trick. Up to you how many cavities (the number of connections) you'd like. I used a six cavity connector for the ability to add an ECU generated vehicle speed signal and RPM signal at a future date. Four cavity is fine if you will never take that option.

Connectors B&C - These need to be weather sealed since they're located under the truck. 150 series 2 cavity is enough to get the job done.

Connector D - You can get away with a 2 cavity Metri-Pack 280 series that has a max continuous 30A rating. I've been using a 2 cavity Metri-Pack 480 series which has a max continuous 42A rating for added security. Just make sure the connector is weather sealed since it'll be in the engine compartment.

Connector E - A 150 series 2 cavity unsealed. You can use something even lighter weight if you'd like since both connections are moving small currents.

Connector F - A 150 series 3 cavity unsealed. Again, substituting something lighter would be fine based on the very small currents involved.

Finally, a quick note about ordering connector components. Always order more terminals than you'll need. I go about 20% more to cover my errors as well as errors on the part of the supplier. It sucks to be near the end on a wiring job and run out of supplies. Chances are you'll run out of the item that's impossible to find on the local market. By the way, unless you're lucky, buying anything connector related on the local market costs 5 to 10 times what it does when ordered from Mouser, Digi-Key, Watek, etc.

[jpstaub]

It may be tempting to leave out the OBDII connector but you really want it. It allows you to pull diagnostic information as well as to turn your motor into a fire breathing monster with the appropriate tuning. It's the interface with the brain that's running the show.

You can find all the information regarding part numbers for the connector in the Delphi Global Connector Catalog on page 2.18. Just be careful about the Tangless part. You've got to use Tangless terminals with the connector.

I put the OBDII connector on the metal plate that's under the steering column. Locating the connector on the end that's nearest the driver's feet makes for a clean installation that no one will see.

For power find the pink wire in the dash instrument panel wiring harness and tap into that (it should go to the instrument panel printed circuit board connector). Place terminal in cavity #16 (the connector is labeled with tiny numbers; you'll probably need good light to see them).

For ground, look for the ground connection that's behind the dash (probably to the right of the hole for the instrument panel). It's a little metal clip that clamps to the dash panel. Or, you can use a multi-meter to test the printed circuit board connector terminals for ground. Ground a multi-meter probe on the dash metal then go around the horn on the printed circuit board connector looking for continuity. The wire of interest should be black (be careful; there's another black wire on the connector that's used for the charge gage trucks; it's natural state is +12V). Tap into the ground wire. Place terminals in cavities 4 and 5.

Throw a terminal wired to computer terminal C1-58 into cavity 2 and you've got OBDII diagnostic/programming capability.

[jpstaub]

Why on earth would you want a check engine light (MIL)? Those things are just a giant pain in the ass. Well yes. For those that can't fix trucks. For a lead pipe swinging motorcycle chain whipping maniac putting an LSX engine in a classic truck that doesn't apply. Still, I realize that there are those who prefer to guess and not know that something is wrong.

For those who want to know when something is wrong and who have an instrument panel with gages you're set. What we're going to do is turn the TEMPERATURE light into the check engine light.

1. Follow the two traces associated with the TEMPERATURE light on instrument panel printed circuit board back to their origins. One should lead to the printed circuit board connector terminal with the pink wire in it. That's power (+12V).

2. The remaining trace should lead back to the printed circuit board connector cavity without a terminal in it. That's the light control (ground).

3. All you need to do, my fortunate lead pipe swinging friend, is wrap a printed circuit board terminal around the "MIL CNTRL" wire and send it home.

The power of k-nowledge has already been covered. That's why part no. 2984794 from Terminals & Connectors is going to save you boku research hours which can be plowed back into actually building your rig. Hint: remember what I said about ordering more terminals that you need.

[jpstaub]

I forgot to specify the key power connector on the wiring diagram included in a previous post. You'll need a sealed single cavity connector to connect to the stock ignition wire.

[jpstaub]

In order to do right by your new engine control computer you'll need to provide it a brake pedal status signal (brakes on or off). For brakes off the computer is looking for +12V. For brakes on the computer is looking for a floating line (near 0V). The way you handle this problem is by installing part no. D850A in place of the original brake light switch (it's located above the brake pedal). A picture of this component is included below.



Note that the switch has two sets of terminals. The set nearest the threaded portion of the enclosure is the set for the brake lights. The set of terminals at the opposite end is the set for the computer.

1. To keep things neat and tidy take the power for the set of terminals for the computer from the set of terminals for the brake lights. In other words, connect a jumper wire from brake light power wire (it should be orange) to either of the terminals for the computer (it doesn't matter which).

2. Connect the "BRAKE SW" wire which should be wired to computer connector C1-33 to the remaining terminal and you're set.

Incidentally, this same switch is used to control lock up torque converters when upgrading to a 700R4 for instance. It's somewhat consistent that C1-33 is labeled, "TCC Brake Switch Release Switch Signal."

What happens if you don't wire up the switch to inform the ECU of brake pedal status? The vehicle will tend to stall as there is an increase in power programmed into the computer that compensate for additional engine load that results from additional torque converter load when the vehicle is under braking.

To make connections simple spade terminals will suffice. I spent some time looking for an actual connector but couldn't track one down. Maybe somebody out there knows what to use.

[jpstaub]

The best place to pass wires through the firewall is where you removed all the wiring associated with the old electric controlled choke. If your truck didn't have wiring for an electric choke what I'm talking about is the rubber grommet to the right of the speedo cable grommet. Not only is the hole for the grommet big enough to pass a sizable connector through, but the grommet has a hole for you to pass wires through. Just remember to pull the wires through the hole in the grommet before you put the connector on the end of the wires. Disregarding that last bit of knowledge is self correcting. No need to over-think it.

By using the above method to route wires the wiring appears stock so long as:

1. You route the required wires through the wiring harness on the driver's side

2. Follow the windshield washer lines up to the cowl trough

3. Run the wires in the cowl trough to and through the appropriate grommet.

[jpstaub]

If all the wiring stuff isn't sinking in or you're at maximum frustration with diagrams, components, and part numbers there's hope yet. Depending on what's happening on my end and when you need the harness back, I may be able to set a harness up and put a kit of parts together to the point where you'll feel comfortable doing the installation. Send a PM and we may be able to work something out.

There are also off-the-shelf options available. Painless wiring is one well known supplier.

[jpstaub]

If you'd like to know more about fuel system design for Electronic Fuel Injection (EFI) applications click here for a great link that informed the design presented earlier in this thread. It's a MegaSquirt produced document that has the basics as well as advanced information related to injector sizing etc.

[jpstaub]

Lets say you drop the rear end mounts and you find a nice rust hole in an axle tube. Now what? Businesses like Currie Enterprises can replace a tube but if you're not near them shipping not to mention repair cost is going to severely cramp style. What about a new unit? Mucho dinero. What about another stock unit? They're like hens teeth these days (one place I called actually said they recycled all that old stuff!). Going with a C10 twelve bolt from '73-'87 may be the best alternative. Everything swaps over with little struggle. The spring perches and shock mounts will have to be replaced but a good shop, personal or professional, can handle that action.

MOR-85090 and CUR-CE-7020 will fix you right up.

[jpstaub]

To move the spent fuel/air mix that you'll be generating with an ultra-cool LSX installation Heartthrob Exhaust makes a dual kit for 4x4's. The system is 2.25" which falls under the magic 2.5" threshold for those sensitive about seeing a smallish diameter exhaust pipe. Heartthrob may be able to make a 2.5" system if you ask nice.

At 2.5" the real question is will the system make it by the transfer case on the passenger side? I think it's possible but it'll be tight. The 2.25" system I installed gave me room enough to work with so I didn't have to be absolutely perfect with the custom Corvette manifold connection.

Aside from the really crappy guillotine clamps (replaced with band clamps) and hangers (fortunately I had some universal mounts on hand to use as tailpipe hangers) one thing about the kit I'm not wild about is the tailpipe location. It could be that I didn't mount the system as intended but the tailpipes hang lower than I'd like. Take a look at the picture below to see what I'm talking about.



For less than $250 it's a good system but if you're looking for a super nice installation it's probably worth going another direction. The pipes I had bent for the driver's side and passenger's side were 60" and 24" long respectively. Expand the passenger's side to 2.25" ID (inside diameter) and you shouldn't need to buy anything else in terms of tubing. Be sure to take the Corvette exhaust manifold flange and donut to the exhaust shop when you go to have custom pipes bent so you can explain exactly what you want. As far as shape of the pipe required, I used aluminum K&S hobby size tubing that you can find at most hardware stores for the exhaust shop to use as a pattern. Shape it the way you need and the shop should be able to duplicate it. Try to keep the bends in one plane if possible otherwise the level of difficulty to duplicate ramps up quickly (now you know how to foil Chinese duplication efforts).

[jpstaub]

I mentioned this much earlier in the thread but the Pacific Fabrication cross members requires at least a 2-2.5" lift on the front end to provide sufficient suspension travel without cross member interference. I used Skyjacker components both front (2.5" springs) and rear (2.0" blocks).

Mistakes:
1. Not ordering the full lift kit together because I thought I had components on hand that would work.

2. Thinking I could use the brand new Energy Suspension spring bushings I put in the stock springs on Skyjacker lift springs (part no. SJA-C225S) because the spring's width at mount points would be the same. Wrong.

3. Thinking I could use the brand new stock shocks on a truck lifted 2". Wrong.

4. Thinking I could find Skyjacker lift spring bushings (part no. SE11C) the same day. Wrong.

5. Thinking I could find Skyjacker lift spring bushings without a diligent research effort. Wrong.

6. Thinking that once I got the Skyjacker lift spring bushings the springs could be installed by installing the bushings then installing the springs. Wrong. The front shackle sleeves had to be shorted by 0.25". I didn't bother with the rear shackle sleeves.

7. Thinking that once I got the Skyjacker lift blocks (part no. BUK2080 SK) I could just install the blocks. Wrong. The u-bolts had to be shortened which is a lovely job to do by hack saw.

Overall, the Skyjacker experience for me was horrible. I'm new to working on 4x4's so all the above may be a given going in. I'll rely on those in the know to fill a noob in. If all the ill fitting parts and terrible supply chain are normal I guess I'll have to suck it up. If not, I'll avoid using Skyjacker products again in the future.

[jpstaub]

This is the way the engine compartment looked before.




And this is the way the engine compartment looks after the retrofit.



The owner is extremely happy with the way the project turned out. I am too. The truck now runs like a raped ape and will do so all day long day in day out. And when the engine isn't feeling well there's diagnostic help available via the engine control computer. It's up to someone else to make the truck look as good as it runs.

[jpstaub]

One note about engine codes. If you're getting P0171 and P0174 before you go down the rabbit hole and replace things like intake manifold gaskets it's worth examining your power brake booster. A bad or failing power brake booster will result in a vacuum leak big enough to give the engine control computer fits and make it throw P0171 and P0174 which are "engine is running too lean," codes. They typically appear at idle because that's when you actuate the brake pedal which may have a leaky power brake booster attached to it. Also, the engine notices a vacuum leak at idle more than at WOT do both to the amount of vacuum available as well as the quantity of air flowing through the engine. At WOT a small amount of air leakage doesn't matter relative to the large amount of air being ingested. At idle a small amount of air leakage matters relative to the small amount of air being ingested (the old theory of relativity).

To determine whether or not the power brake booster is to blame warm the engine up to a point where it operates at a low smooth idle. Now depress the brake pedal. If the engine RPM changes noticeably (you can hear the change) then settles back to the original idle after you release the brake the problem most likely lies with the power brake booster.

You can do the same type of diagnosis in a more advanced way by hooking up to the ODBII port and using a computer program or reader to display the Mass Air Flow (MAF) sensor reading. Note the number at idle. It should be relatively steady. Now depress the brake pedal. If the brake booster is bad you'll see the MAF reading drop significantly. After the brake pedal is released the MAF reading should return to close to its initial value.

It's not necessary to look at fuel trim but it's interesting to see what the computer tries to do to compensate for a vacuum leak. Because the MAF reading drops with a vacuum leak the computer thinks it needs less fuel. But the O2 sensor tells the computer it needs more fuel to keep the engine running. The fueling value is based (in part) on the MAF reading which the computer uses as a reference then trims according to the O2 reading (under certain conditions which won't be covered in the interest of brevity). With the vacuum leak that produces an abnormally low MAF reading the computer pegs the trim (there's an upper limit set by the program) based on the O2 sensor to compensate. Eventually P0171 and P0174 codes are tripped because the computer can no longer add fuel based on what the O2 sensor is telling it.

[jpstaub]

OK. That's about all I've got to say about the project that I think is worth while. If there are specific questions out there let me know and I'll do my best to give an answer/more information. LSX swaps really are as good as everyone says they are. The power, reliability, and efficiency can't be touched by early model stuff. Overall, the cost is pretty competitive to boot. Even if I were going to build something without fuel injection I'd build it based on an LSX foundation. It is awesome. Generous Motors did it right.

Finally, I'll offer a Swap Resources.doc I put together before I did my '72 C10 LQ4/700R4 which was my first LSX swap. The document has a lot of good information for those that would like to do a bit more reading. I highly recommend the reference by Pirate 4x4. They put something together that's every bit as useful as the connector document I referenced earlier. You can't rely on the uninformed to stear you in the right direction. After reading Pirate's series you'll be one of the most well informed anywhere you go. Due diligence is king.

Best of luck with your build,
Jake

[jpstaub]

I thought I was done then I remembered the LQ4 fuel injector connector part #829-15326181 which is in the diagram below.



Parts recyclers are not known for being cautious when it comes to ripping wiring harnesses off of engines. Among connectors most likely to be broken are the fuel injection connectors based on their delicacy. Spend $1.95 at Mouser and save yourself $28 on each connector. I'm not kidding. The parts store wanted around $30 per connector for these (if it was actually the right part).

Don't be a lamb! It's too damn expensive.

[jpstaub]

And finally, what to do about the transmission filler tube? It's a problem because there's no hole in the LSX bellhousing pattern into which a bolt can be inserted to pick up the stock transmission filler tube bolt tab.

While Generous Motors tooketh a bellhousing bolt they gaveth plenty of holes in those slick aluminum cylinder heads you get to use to make ample power. Remember this guy pictured below?



It just so happens the studded bellhousing bolts (part no. 15724226) also fit into the holes on the back of the cylinder heads (there's a shorter version of this bolt but I don't know the part no.). If you use a studded bolt and the right size rubber lined clamp (picture included below) you'll have yourself a mounting solution that's every bit as solid as what came out of the factory.

[jamesjones]

Bumping this thread because it's loaded with invaluable information and the OP deserves some props.

[72MARIO]

bump for a very well detailed build.. ls swap info help