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Page 15 of 15 1 2 13 14 15
Re: 1997 Chevy Express Cobra Conversion
1983 G20 Van #802119 March 11th 2023 8:34 pm
Joined: Jul 2019
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I'm still trying to keep my fire going in my cave. That pesky T.Rex keeps coming around; I can't get a break lol

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Re: 1997 Chevy Express Cobra Conversion
1983 G20 Van #803084 April 25th 2023 2:08 am
Joined: Apr 2007
Posts: 249
Likes: 59
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G Van Man
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Decided against the $800 TCM 2650 interface to run the 47K mile 6L90E I recently acquired. Instead for a small amount more $, I am going with an E67 PCM for a 2009 Trailblazer SS and a 58x conversion with drive by wire and coil near plug ignition. Seems like a better option to update the engine management and get a new engine harness at the same time.

I found probably the last new GM 2016 L96 6.0L Express van engine harness for $300. Scored one of the last new GM E67s for the Trailblazer as well for about $285. Finally I was able to find the OEM service manuals for my 97 for $48 shipped still sealed in plastic. I also downloaded a ~950 page PDF file from the GM Upfitter site for the 2016 van. I also found the 2009 Trailblazer SS engine wiring diagrams for $6.00 from an online site specializing in harness diagrams. Going to repin the 2016 E78 van harness to use the E67 and rewire my vans current engine harness to accept the trimmed down 2016 harness.

I am going to build a standalone transmission harness for now to run the 4L85E with a T42 TCM for a ~2010 Express van. Get my van wired, running and tuned with the E67 swap. Then when I finish acquiring parts for the 6L90E swap, it will be a simple wiring operation to swap the 6L90E in place of the 4L85E. The T42 TCM runs nearly completely on its own via 2 CAN bus wires to the PCM with the bulk of its connections being to the 4L85E itself. The 6L90E uses a T43 mounted directly on the valve body inside the unit and has an even more simplified wiring setup. I am leaving the T43 connections in the 2016 harness and will merely unpin the 2 CAN bus wires. To put the 6L90E in action, will have to move 2 wires back to the PCM pins after removing the T42 setup.

I thought I was going to have to buy new Molex connector bodies for the E67, but the E78 ones are the exact same. Just have to repin the E78 harness for the E67 PCM and trim out the 2016s body harness and fusebox wiring to marry to my 97s body harness wiring. I will probably repurpose one of the un-used body harness multiple pin connectors and get the matching connector and pins to it to connect my existing harness to the new engine harnsss to allow for easy engine harness removal in the future should future repairs be required.

To make my Gen1 SBC talk GenIV LS is fairly simple. The 58x reluctor wheel is an off the shelf EFI Connection part. The cam sensor setup is an off the shelf GMT900/late model Express 4.3L V6 part consisting of a distributor drive and cam sensor. The flat response knock sensor adapters are also an off the shelf marine part as well as a EFI Connection part. They are either machined studs or bushings that thread into the block drains on the SBC and a pair of $20 LS2 style flat response knock sensor bolts on to them.

The drive by wire accelerator pedal from a later model van bolts right to my firewall. The 4 bolt 90mm LS2 style throttle body bolts to my 3 bolt intake with a normal LS 4 bolt to 3 bolt adapter plate. The LS coils can be mounted remotely and hooked to normal plug wires to run the SBC. I happen to already have a DBW pedal, DBW 4-bolt 90mm throttle body and several sets of LS coils.

It looks like the 6L90E will bolt in using a 98-02 4L60E crossmember for the later 4L60E, a newer 6L90E van driveshaft, trans cooler lines, shift cable, filler/dipstick tube and dipstick will also bolt pretty much right up. I intend to get the newer shifter with tap up, tap down, and tow haul integrated as well as a CAN bus module that integrates the tap shift/tow-haul and reverse light output into a single module. My cruise control switches and VSS outputs for the cluster and ABS are able to be directly wired to the 2009 TBSS computer as well, preserving their functions.

Finally the TBSS computer will also still run my PWM controlled EV fan clutch because it is from a Trailblazer, simple enough. I will use the newer van 02 sensors that match the connectors in the harness. They are under $30 ea and my old 02s could stand to be replaced anyway.

I have found an interesting thing I did not know as well. With the PCM and TCM I plan to run paired together in the CAN databus, HP Tuners will read the E67/T42 or E67/T43 pair for the base tune and allow me to tune both as a matched pair.


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Last edited by 1983G20Van; April 25th 2023 2:32 am.

1983 G20 Conversion Van, 350 TPI, Reed Hydraulic Roller cam, Ported 906 Vortec, Edelbrock 3817 TPI-Vortec Base, Doug Thorley Tri-Ys, Dual 2 1/2" exhaust, Speed Density 7730 ECM tuned by ME, 700r4 by ME, Stock 1,600 rpm converter, Rebuilt Stock 10 bolt with posi by ME, 3.08 gears, 358 RWHP @ 5,200, 384 RWTQ @ 3,400, 14.66 @ 95.43 w 2.28s 60'
Re: 1997 Chevy Express Cobra Conversion
1983 G20 Van #805917 August 26th 2023 3:30 am
Joined: Apr 2007
Posts: 249
Likes: 59
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G Van Man
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With it being so hot here in Texas, decided to tackle my failed rear expansion valve and replace the Variable front orifice that was acting up at highway speeds. Grabbed a White GM 0.072" orifice tube and expansion valve from Oreilly for a 97 Van, forgetting the rear unit is aftermarket. Pulled the old valve, Oreilly had closed, 11 PM trip to Autozone. Interchanged the numbers and it crossed to a Four Seasons 38693. Local Autozone had it in stock. Installed the thing. Evacuated it, then recharged. Seemed to be working ok that night.

Next day it was 109°F and barely cooling. Check the pressures and the low side was over 60 psi. I recovered the system and put an Orange Ford 0.057 orifice up front. Slight improvement. I started searching around and realized the suction line off the rear evaporator was frosty almost all the way back to the compressor. Either a defective valve or badly calibrated.

Went to Old Air Products and picked up a USA made expansion valve they build for their similarly sized Hurricane unit. I also discovered the Sanden SD7H15 is only 155cc displacement. The OE HT6 compressor is 170cc. Then found a Four Seasons 88947 which some sellers are claiming is 210cc. Oreilly had one in stock.

Thought to myself, the 87 G20 needs a new compressor on the L31 I built for it. The 87 is front only air and the smaller Sanden should work great on it. So I went and bought a new 88947. Took back the wrong expansion valve, picked up the compressor and a Red 0.062" orifice tube. I have had the best cooling out of this van over the years with the Red tube, the van just likes them.

Installed the parts, vacuumed it down and recharged it. Pressures are much better. Initially it was cooling at 50°F at idle with both blowers on high. Brought it up to 2,000 rpm and held it for 3 minutes, 36°F. Took it for a test drive, 10 miles mixed highway and city, got down to 30-32°F and stayed there. Nice to have a properly function AC again. Incidentally, rolled over to 6 figures on the odometer today as well.

https://youtube.com/shorts/ayygjqA2pvc?si=F4CYByupzM_t6AHd

https://youtube.com/shorts/A7D-sJq9PPQ?si=V02VeBJJKVX4U5k_

https://youtube.com/shorts/o86VVHxqH-4?si=313E0j6Hm0uMfmkW

https://youtube.com/shorts/QZJhuNXfLmc?si=upppZrrO--2ginW1

https://youtube.com/shorts/msL17b8nppw?si=q6dyLoV9YFNxe5-w

Last edited by 1983G20Van; August 26th 2023 3:32 am.

1983 G20 Conversion Van, 350 TPI, Reed Hydraulic Roller cam, Ported 906 Vortec, Edelbrock 3817 TPI-Vortec Base, Doug Thorley Tri-Ys, Dual 2 1/2" exhaust, Speed Density 7730 ECM tuned by ME, 700r4 by ME, Stock 1,600 rpm converter, Rebuilt Stock 10 bolt with posi by ME, 3.08 gears, 358 RWHP @ 5,200, 384 RWTQ @ 3,400, 14.66 @ 95.43 w 2.28s 60'
Re: 1997 Chevy Express Cobra Conversion
1983 G20 Van #806385 September 15th 2023 8:16 pm
Joined: Apr 2007
Posts: 249
Likes: 59
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G Van Man
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Took a page from the GM engineers of the newer Camaros and HD trucks. My 97 now has what GM engineers call a Flowtie to help get cooling airflow to the transmission cooler.

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1983 G20 Conversion Van, 350 TPI, Reed Hydraulic Roller cam, Ported 906 Vortec, Edelbrock 3817 TPI-Vortec Base, Doug Thorley Tri-Ys, Dual 2 1/2" exhaust, Speed Density 7730 ECM tuned by ME, 700r4 by ME, Stock 1,600 rpm converter, Rebuilt Stock 10 bolt with posi by ME, 3.08 gears, 358 RWHP @ 5,200, 384 RWTQ @ 3,400, 14.66 @ 95.43 w 2.28s 60'
Re: 1997 Chevy Express Cobra Conversion
1983 G20 Van #806463 September 17th 2023 11:08 pm
Joined: Jul 2019
Posts: 11,241
Likes: 411
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That's cool ( no joke intended )

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