My 91 Trans Am convertible has shifted from minor service to a semi major build

The goals for this build are:
More reliability including easy to troubleshoot. No more paper clip counting flashes
Improved efficiency. Whether that's more power, smoother running or better MPG, time will tell
Simple tuning and room to expand. 305 -> 350, 700R4 to any trans type, cam, headers etc all simple to tweak
Try to keep the costs reasonable

How I plan to accomplish that:
Crank trigger
Vortec distributor for the cam signal. No plug wires will be attached
8x LS coils

 

First up was the crank signal. An easy solution would be to use a dual sync distributor. Down side is cost
This is a low buck approach that can use used for literally any engine

The reluctor wheel is off a junk LS2 crankshaft I had laying around. New ones are <$40
I had a local machine shop bore the center to be a slip fit around a TPI crank pulley
Both were sandblasted for a better weld
Holley states for 58x trigger wheels, at TDC the sensor should be set between 9-12 teeth before the flat. This can be fine adjusted later in the tune


I missed a photo halfway of the reluctor not welded on. A simple bracket was fashioned from scrap .090" metal and bolted to the bottom of the serpentine bracket. With the sensor roughly in place, the trigger wheel was rotated within the adjustment window, marked and welded. Sensor to wheel gap was adjusted by adding washers



A simple bracket was needed to adapt LS coils to the SBC valve cover




This is what I came up with. Scrap 3/4" sq tubing with a few notches and two tabs welded on. The DR side needed a droop and uneven coil spacing to clear the oil fill. Standard 12" LS plug wires fit perfectly

 

I got a good deal on a HP ECM and 4bbl EFI unit. Way more ECM than I need, but couldn't pass it up at that price. The X Max ECM and flying lead are from my AWD build. I'm wiring it for an X Max so a 4L60E swap wouldn't require a rewire. The misc connectors are from my harness building days along with a few Holley specifics from low dollar motorsports. The yellow box is a 3rd gen VSS buffer. I'll need that to keep a functional speedo



First up is how to mount the ECM. The stock tray is pretty darn close. Just trim the tabs and drill for mounting screws
I'll be using the X max for mock up and run the HP ECM as long as the 700R4 is in the car. If I go 4L60E, then I'll upgrade the ECM. Wiring will be present for the electronic trans



Now to prep the flying lead. It comes as the two main ECM connectors, 15' of wire and the correct shielded bundles for CRK, CAM and WB02



To start, I like to hang it up high and slice all the tape off. It's easiest to separate the two connectors and depin unused wire now



Press on the little white detent and the little red wire connecting the two connectors can be pulled free. This separates the two for easier modification



Pull all the wires that won't be used. Use a holley pinout to help. You have to know what components you will be using from the start. EX: a hyper spark distributor wouldn't need 7/8 of the coil wires. 4bbl TBI units can remove half the injectors. All the points wires can come out

*insert holley diagram

I also like to change some wires that will be used
Fuel pump relay enable is red, which is confusing to power wires
Tach is blue/wht. I trade out an unused points wire which is white
The CAN wires are 15' long. I swapped in a shorter pair from a different harness build to save this pre-twised set
All the programmable inputs are removed for this build. The only common input I run is for AC feedback, which this car will not be using


These are going back in
Shorter set of CAN wires
Scrap pink wire for ECM 12v, original was red/wh (confusing)
Tan/bk for fuel


Snapped back in place. CRK/CAM voltage is still pulled free


All the wires are now separated into groups. The sensor set includes 5v (ORN) and sensor low ref (BLK/WH)
The 5v is pulled up slightly to easily join the CRK/CAM voltage


Now the CRK/CAM voltage wire needs to be addressed. I prefer to extend it for any setup as the supplied wire is soooo short
For 24x/1x LS setups, it needs 12v on connector B like it was originally
For 58x/4x LS setups, it needs 5v (ORN wire)
For oddball setups like my 58x/1x, it needs 5v
6x, 12x, 36x, etc crank triggers can be either, or 2 wire VR without a base voltage


CRK/CAM voltage tied into sensor 5v

 

That's if for connector A


Connector B goes much like A, but much less comes out. Only using output #1&2 for speedo and fans
Coil low ref (BLK/YEL) needs to be teed into for the CAN connector. That's the only splice for this connector



The two connectors are taped together and two pink wires pulled for INJ/Coil fuses. They will go to the C207


The trans side needs to be made from scratch. Low dollar connector/terminals and wire from my shop. The holley trans pigtail is both expensive and too short for a 3rd gen. I used GM colors vs holley. There was one splice for the TFT and VSS low ref


Joined with the rest. The short bundle on the left is for the C207, plus the brake switch input wire


Find the relevant diagrams in this thread
https://www.thirdgen.org/forums/ltx-...-diagrams.html

The main bundle gets a little loom and is ready to fit to the car. Notice the twist along the main trunk. I've found that this keeps errant wires from popping out without detracting from the flexibility


Plug it in and install the bracket



An old pass through was hollowed out and snapped on. It can be injected with sealant or left as-is. This cabin will never be water tight, so I probably will not be adding sealant



Going over or under the HVAC box is personal preference. A cheap insulated clamp will hold it in place

 

Now the real harness build begins. A reference point is needed to begin branching pigtails. I draw an imaginary line from the base of the intake rearward (white tape)




I drew a quick reference chart for the sensors to begin splitting the 5v and low ref wires in the sensor bundle




With a game plan made, the 5v/low ref wires can be split among the 8 sensors. There isn't enough blk/wh or ORN wire in the flying lead harness. You'll have to supply some


The individual sensor wires can be grouped with their respective 5v/low ref and roughly pointed where they need to go


Time to shape the harness

 

Split power for the injectors and coils. Estimate about halfway along the fuel rail on each side

You can see the harness branches taking shape

12v to the 4L60E is a little different. A drawback for holley is it doesn't have internal diodes to prevent backfeed situations. This was band-aided later by putting a relay on every power source in their supplied harnesses
I prefer a simple diode. The S shape is tension relief because the splice will live in a pretty flexible section of the harness

The rest of the C100 wires are pulled for starter, gauges, grds and some loom begun. Also pulled the alternator wiring

Starting to route the main branches. The PS main branch will be the most complex with the full sensor group and injectors. For LS, it's drivers side

Injector and sensor break outs set. Most of the excess wire is trimmed off to be manageable

Injectors first. These pull to seat EV1 connectors aren't the most user friendly

Drivers side finished

PS sensors finished

 

The end is in sight!
The C100 bundle gets terminated. Power cables and fuel pump 12v move forward along the fender rail

The battery tray area is the last part. There's alot going on in such a tight area
The fuel pump relay wires are pulled out and terminated. 3rd gens all have an external fuse protecting the circuit, so that's directly behind it
The remainder are all power cables and fan control wires
This is an amazon power distribution block, aka busbar


Top side is finished. Trans tunnel branches and the C207 are all that remain

 

You make everything look so easy! Great work. How are you at wiring up the ac system?

I'm going with the 0411 pcm out of an 02 express van with an efi connections wiring harnesses (4x reluctor ring). I'm wanting to replace the pancake compressor with a sanden compressor but I'm not sure how to wire it up. Also the new wiring harness has done away with the connector for the pressure sensor in the hard line and I'm not sure if I should add that into the harness or leave it out.

 

For that setup, I'd swap the fan switch for a binary to combine high/low pressure into one. Fan override will come from the 0411 PCM and doesn't need to be a physical switch

 

nice build and great move on how to mount the reluctor wheel... did you consider instead of the holley, just bore out a 24x wheel per your method and run a easy to find / cheap / capable 411 ECM?

 

Yes, a basic 0411 PCM was considered. 15 years ago, I would have absolutely done that, but the number of competent tuners in my area has drastically fallen off since. Holley is simple to setup and troubleshoot

 

Finished up the wiring

Trans (R) Coils (Ctr) Crank and WB02 (L)



Oil sender and harness tucked away from the exhaust. A 3 wire oil sensor was wired in, but I don't have the sensor installed yet


Crank sensor finishes up underneath the car


ECM power and C207 wires


Terminated
3rd gen VSS buffer wired in because of the 700R4. TCC wires aren't populated in the computer yet. I'll figure those out after the engine runs


That wraps up the main electrical system. Fluids and test fire coming soon

 

Added a fuel pressure sensor, but couldn't find a simple adapter

The schrader valve to fuel rail uses 5/16" 18 threads which is a common bolt size, but near impossible to find fitting size




Easy solution is to drill/tap the rails to a more common 1/8" NPT. Then a common 90* fitting can be used




Important! Need to make sure this tiny hole isn't blocked by the new fitting or the sensor won't see any pressure



Rails cleared of debris and reassembled

 

Next up, I installed the trans and couldn't bring myself to reinstall the original T-pipe

I spent way more time than I should have looking for stainless manifold flanges, but couldn't find anything that matched up. So, I welded the first few inches of the old exhaust onto the new system
This was much more time consuming than first expected. The universal kit comes with straight, 45, 90 and 180 bends. None of these bends could be used as-is, everything was custom cut




Preparing the merge. Two pipes welded together in the in-accessible area
This was a first try on the merge with a basic 3" to 2.5" reducer. I didn't like the step and the fill-in section would be too much. Fail




I ended up using two 90* bends. I sliced the backside off one, and the inside off the other. Lots of hammer forming





A scrap section of pipe was sliced longways and hammered flat. It was used for the small fill in triangles
The tip at the base of the merge was cut off to trim back the overlap areas. Made an attempt to keep turbulence down




That's a wrap
I left room to add a cat if I end up hating the sound
The cat-back is already done with a magnaflow muffler





Lots of little things to put back together to get her moving

 

Would that binary ac switch go in place of the original high pressure switch or low pressure switch? Or does it not matter what location it goes in? This is my first time messing around with a new ecm and ac, other than recharging the system. Ill probably start a thread for more help on this when I get closer to installing everything.

I'm following this thread to get some what of an idea on my 0411 upgrade. Once again you do nice work and I get a ton of helpful info from your posts!!

 

Woo first fire

Had a few issues to sort out due to me rushing through this

Crank sensor was pinned incorrectly. My eyes aren't what they used to be and I got A&C reversed

Got RPM signal, but no fire
Found the goof in the ignition settings. I had setup a custom crank input with LS 58x and single pulse which is what I'm actually using. I was confused because it didn't allow picking the TDC tooth
Switching to 60-2 did the trick. Pick the tooth and do fine adjustments in the timing offset box


This allows for total adjustment of the crank trigger to sensor alignment. The wheel could have been welded on in literally any orientation. Would have to manually count teeth to where TDC ended up and change the setting accordingly



Now that she runs, it's a matter of fine tuning to complete the build

 

Wow, very creative way to do it. Wish I had thought of using an old LS trigger wheel and a distributor for cam sync. Bookmarking this for any future builds.

My guess is that your all in cost is dramatically lower than buying the Holley SBC hardware. Their crank trigger and cam sync alone are probably now over a grand, so big money even if you opted for used coils and their unterminated generic harnesses. Stuff adds up quick.

Plus the Holley SBC stuff doesn't even fit or line up without non-trivial mods. To which they reply "it's off-road only", if you can even get someone on the phone to give a non-answer.

Anyway, nice work. This is the way to go.

 

My cost on the hard parts is relatively low
~$150 for the crank/cam trigger setups

Wiring/ECU are dealer price

Holley has D/C it's SBC crank trigger kits. Only off the shelf options are EFIConnection's SBC 24x/58x kit or a dual sync distributor. Looking at $500 each either way

This setup is also entirely universal. I use a similar method putting Holley on Corvair flat 6's and am prototyping a olds big block for a GMC motor home

Just keeping things simple

 

Two more items on the docket:

PWM fans
TCC control

Here's an overview of the install

 

Nice- that's a great price all-in for the hardware. My crank trigger alone was 3-4x that.

I didn't realize anyone still worked on Corvair flat 6s. My dad and uncle used to race them back in the 70s. Pretty cool and unique cars, but very obscure these days.

 

My shop shared a building with Chair City Corvair Center until they moved a few months ago. For an older niche car, they're still surprisingly popular
They started with the Brown TBI conversions using mircrosquirt, then we developed Holley terminator control. Now, they're using Cartwright port EFI systems and Holley control. It's pretty neat how these things come together

Anyhow, I got a PWM fan from a 2010 ish Ford fusion. Almost perfect fit for a 3rd gen radiator. The lower shroud needed to be bent down with some pliers and the standard hold-down trimming. Otherwise perfect





My tuner dropped by and put a professional touch on the file
She's buttery smooth now. Really hard to believe it's a stock LB9
Needs a cleanup before the glamour shots to close out the project

 

That fan and shroud assembly sure looks like it fits very good to the radiator.

 

Very similar to what I'm doing except to a 383 in a GMT400 4x4. Hit the Y in the road between a Terminator X Max or 0411, shop will tune either but prefers the Holley- I'm leaning towards the 0411. Are you still doing harnesses?

 

I'd recommend the holley, just because it's easier

No, I do not offer mail-order harnesses anymore

 

complete off topic question but whats running your headlight motors?

 

The module was moved to the LF corner under the battery tray

 

having had both systems, holley is way better and worth the money lol

 

I edited Pocket's reply above about building his Y merge pipe.

If someone is thinking about doing this in the future I'd highly recommend just buying Magnaflow's 16450 Y-merge pipe instead. The MSRP is $267.00 and you can get it with their 20% off promo code for $213.60 + TAX with FREE shipping from hottexhaust.com.

Magnaflow 16450 | 1986-1989 5.0L/5.7L Chevrolet Camaro/Pontiac Firebird | High Output, Single Catalytic Convertor, 409 Stainless Steel, Mandrel Bent, Front Y Pipe

I can't imagine after buying the parts needed and the time spent fabricating the Y-pipe that it could possibly be cheaper than just buying it.


Magnaflow 16450 Y-pipe.

 

With hindsight, yes the magnaflow piece is the better option

 

just a slight counterpoint... i have used both extensively, the holley has a lot of incredible features, however a couple key things it is extremely inferior to in terms of the 411 include reliability and diagnostics... reliability both in terms of turn the key and your engine starts all the time (ie holley can lose its programming) and core hardware reliability (not saying holley is that bad in this area, but it isn't OEM level)... on diagnostics 411 clearly has way upper hand (i consider this a very nice feature but not the reason i have stayed away from holley at this point).

if holley would just improve a couple things i think it would be clearly the best... i have stuck with 411 as i am not putting up with programming disappearing and their random introduction of software bugs in releases and not being responsive at all which i went through on TPI HEI setup and went back to dyanmic EFI

i think it does come down to what you want to prioritize vs what you are willing to live with... 411 is limited in different areas especially for high capability builds vs holley... the reliability / diagnostics though is where the holley can struggle vs 411

 

I need to do this with my 89. Been on stock tune since 89 and it's way past that now lol

 

Holley Terminator is also a budget entry level EFI. You have to keep that in mind
It has excellent capabilities in that regard for the money

 

I have to be carefull of the 4L60E, does the Holley have some kind of torque management?

Here it's $2400cdn for the Terminator, right now I have everything in a box for the 0411 conversion- just need the ambition (which is in short supply) to do the harness.

 

Updating this thread by adding TCC

There's a dozen ways to wire in the circuit. I went this route because it made sense to me. It draws approx 5a, which is above the limit for holley, so a relay is required



Otherwise, she runs awesome. Huge improvement in low/mid range responsiveness. I'll start tinkering with lean cruise to try and squeak out a little better mileage
The cam sync from the custom ignition parameters is kind of annoying, but that's really my only gripe
Really happy with how the system turned out