This wire harness stuff was a lot more involved than I had anticipated, this one is on par with the K2500 stuff I did.
The Cavi PCM is mounted on the passenger side right behind the headlamp inside the fender. So all the wires are automatically 1 mile longer by default. I managed to get the engine harness 80% done, just have to interface it to the body harness. Grabbed 2 16-pin wiring pigtails and another 10-pin from a random 2010+ car at the u-pull, going to use nearly all of them for the connection between the Cav body harness and the PCM. I had to add two relays to the relay center for the radiator fans, overall just a crapload of wiring to manage, lengthen, shorten, re-route, find mounting clips, new corrugated shielding, etc. Ended up having to relocate the battery to the trunk as well, was trying to avoid that, but the space limitations in the engine bay are calling the shots now.
What's left:
-body harness to engine harness interface
-exhaust
-random plumbing and hardware
-fluid fill
-put the interior back together because I had to put a different shift cable in and that...snowballed...
Unknowns:
The Cavi has what appear to be an early LAN class 2 data communication circuit (I would call it primitive, but I've actually worked with the 1986 Riviera computer and the 180 baud crap magic). The various modules are connected in a daisy-chain configuration with the BCM apparently the master. Every module connected has two class 2 data lines connected to it, including the PCM. From what I can find, every single module both of the wires are internally directly connected on the Cavi. The Cavi does not have the UART wires (though depending what section of the service manual you reference, they are in the wiring diagrams). There's a ton of data and requests that are communicated via the class 2 buss, A/C request and gauge cluster functions to name a few. My initial research into this project said people used the Regal PCM OS (or I think the Monte Carlo SS one) and "just hooked up the wires and it worked". Well, funny story, the Regal stuff has a single class 2 data line going to each module from a simple splice. The working theory is that the daisy chain approach to wiring doesn't actually matter beyond providing multiple paths to the master module to mitigate potential failure. What's also fun is that depending on the CSM you reference for the 3800 (or in the case of my '98 H-body CSM where one page says one thing and another page says the exact opposite), either of the two effected pins on the PCM are used for class 2 data. So, hopefully the HVAC, gauge cluster, ABS, sensing module, and BCM all play nice with the 3800 PCM which is externally identical to the original Cavi PCM.
The Deets:
Will a brand new a few years ago before the motor threw a rod Cavi fuel pump keep up with an L67? Probably.
Will the A/C work? I had to modify the compressor manifold from the donor Riviera to splice the cavi lines to it. I used an AN union + nylog on the intake side and a weld-on fitting for the discharge side (I have a hydraulic A/C hose crimper tool for the hoses). The compressor and the class 2 data buss functions are the only concerns, though I should probably charge it with some air duster and see if it leaks overnight or something.
EGR? yeah.
EVAP? All of it.
Cruise control? Well, it's all wired up the right way, somehow the only 3800 that the CC has ever worked on was my '86 before I L67 swapped it. So that shit never works, and it won't talk to the Tech-2 to determine why it doesn't work. So I give it a 15% chance at best.
Upper radiator hose: E71947 I think, Malibu V6 hose was a direct fit.
Lower radiator hose: Ok, not very impressed with this, so more to come. I had to make a custom manifold because clearance to the A/C compressor and manifold prevents an OE L67 lower radiator hose from working, and the overflow tank needs a tee off that line as well. I ended up building a manifold from 1.25" copper pipe and fittings, using half of the L67 hose and half of a C71765 hose (IDK what it's from, a go-cart?). The only real concern is how it's going to handle the flex from daily use and the constraint of no room to work with between the A/C compressor and the radiator. It's certainly a creative use of space, I would love to see how any other swap did this without A/C delete.
Heater hose fittings: Referencing the fittings on the tensioners that the heater hoses connect to. The W-body shit are straight fittings and don't work because they will punch a hole in the A/C dryer the first time you hit the gas. The 90 degree fitting from the H-body and E-body cars will fit on the upper heater hose and have clearance to the A/C dryer. The lower heater hose.....Yeah, fudge it, hit up the lathe and the TIG for this one:
Heater hoses: Two e87606 Dayco hoses. Keep it simple..
Throttle cable: Almost yes. You have to cut off the end of the cable and swap on the L67 plastic mount (same as the crap I did with the Camaro top swap). The OE cavi cable is long enough to make the L67 plastics fit and weld on the barrel fitting.
Cruise control cable: 99 W-body cable will work though its tight.
Shift cable: N-body AC Delco 22678830 will work, as will the console shift '92-'99 H-body cable (which is out of production and not obtainable aside from rusty used parts at the moment). With the N-body cable you need the N-body trans bracket, weld it on to the 4t65 bracket about 1/4" further away from the shift lever. The N-body cable is an exact fit to the J-body shifter and firewall pass-through. The H-body grommet needs to be modified to fit the firewall, though appears to fit the J-body shifter and the 4t65 bracket. I opted for the N-body cable since I was able to get one new.
Battery: In the bin! I mean, trunk!.. Grabbed a Mega 250 amp fuse and holder, some 0 gauge THHN wire and junction blocks. The stranded THHN wire is going to be solidly mounted between a set of junction blocks in the trunk and under the hood. Original 3800 battery cables between the battery and junction blocks, and between the block/starter and junction blocks. Before you whine about amperage ratings - yes, all of the amps will find their way through all of the wire! Everything from 1000-1900 watts is what I've been able to find for the 3800. It's effectively a momentary load, in the case of my Montana the starter cranks for well under 1 second. So, you know, perfectly adequate, since the GM remote mount batteries use 2 gauge welding cable with far more strands and less current capacity or something like that.
Front Brakes: Cadillac JL9 (STS/CTS/SRX) 12" dual piston aluminum calipers, N-body knuckles and outer C/V hubs, N-body LCA ball joints. J-body WSS connectors fit the N-body bearing hub connectors.
Did I mention, no deletes? Yeah, GM couldn't have done this better, because they didn't.
