99 Chevy 350 Vortec Swap to 88 Truck

[jstutz]

Hello, my son and I are looking to pull a 99 vortec out of my old suburban and put it into the 88 truck we have. We have never done this before and clearly there are some wiring changes that need to happen. Looking for any advice or information to help this along. We have both engines / transmissions out and ready to swap but kind of stuck on the electrical. Any help will be appreciated. See below for some details

1) I have a fully functioning 99 suburban with a vortec setup in it that we want to swap to the 88. We plan to take the engine and transmission. I have access to all the computer / wiring and anything else off the suburban.

We thought about putting a conversion intake on so it would then basically use the TB off the old engine but i think i want to have all the new stuff instead. We have all the hardware out but kind of hitting a roadblock getting the vortec computer hooked up to old truck. They are quite different.

2) would it be easier to put the transmission and engine in together or separate?

I'm pretty sure this swap has been done before many times so if anyone here has any experience or advice, it would be greatly appreciated.

 

[AdmiralYoda]

Let me first ask....what are the overall goals of this swap? Fun project, mpg's, more power, etc? Or just trying to get the 88 back on the road?

The Vortec motor was the last of the Gen-I small block engines. It had slightly better cylinder heads and came with roller lifters and a better engine management system (1st gen OBD-II).

I'd rather rebuild the 88 with some upgrades than go through all the effort of swapping in a Vortec motor with all the harnesses and computers. If a "more" modern engine swap is what you are after, skip the Vortec and go straight to the Gen-III/IV LS. The 99 had a 4l60e so you'll need to use that transmission if you want to keep the 99 Vortec as-is.

That said...here is what I'd do. Start with the Vortec 350 and add an Edelbrock Performer or Performer RPM intake manifold and add a carburetor. Keep the transmission that is in the 88.

 

[redhat]

PCM/computer in the 99 donor vehicle will control both the engine and trans so I’d put them in as an assembly.

Possibly this sites resources will help you: https://www.lt1swap.com/96-99_vortec_harness.htm

 

[dfarr67]

For all the work involved- I would either put an LS in or find the vortec/TBI intake and use the old electrics with newer block. You are going to have to retune the ecu.

 

[DriveHard]

Keep the old transmission, ditch the electronics on the Vortec, and go with a carb intake and a Holley Sniper self learning.
https://www.holley.com/brands/holle...injection/sniper_efi/sniper_4-barrel_systems/

 

[Bud_One]

The 99 requires 60 psi of fuel pressure to start if you're keeping it stock with the port fuel injection.

 

[Nick1994]

If you put the intake from the 88 on the 99 engine, you wouldn’t really need to rewire anything, right?

 

[Chris142]

If you don't install every sensor you will always have a code. The fuel tank evap stuff especially. And that's tough to make work on the old tank. You also must add the cel

 

[clinebarger]

Not that difficult of a swap....

*100 PSI fuel pump on the '88 sender using fuel injection hose between the pump & sender.....You'll have to rework the pressure & return line where they hook to the engine.
I would use the '99 Vortec fuel lines down to where they cross over to the frame & splice into the '88 lines using flare unions (NOT compression fittings!!).

*Use the '99 PCM & Underhood Fuse box, The Ignition Hots (pink) & Battery Hots (Red & Orange) are pretty self explanatory.
*The 4K square wave VSS output from the Vortec PCM will need wired directly to the Speedometer Head bypassing the '88 VSS Buffer Module.
*MIL control circuit ran to where the '88 ECM was & sliced to the original MIL control circuit (Both are Brown with a white tracer)
*The Vortec Fuel Pump Output circuit (Gray) needs to be spliced to the original FP hot wire (Also Gray).....Or it can be spliced to the Green with a White tracer at the original relay.
*ALDL/Data Link Connector needs to be OBD2....Can be mounted under the hood or under the dash.
Pin 2....Class 2 Serial Data from the PCM (Purple wire) Pin 11 of the C4 connector
Pin 4 & 5....Ground
Pin 16.....Battery Hot
*TCC Brake Switch, Purple Wire, Pin 10 of the C4 connector needs wire to the normally closed portion of the brake switch with a Ignition Hot on the other side of the switch (Kills power to the Purple Wire when the brake pedal is pressed to unlock the Converter Clutch)
*The Starter Solenoid wiring will depend on where you want the Neutral Safety Switch....I would use the original '88 column mounted switch & swap in the "Short Shift Shaft" out of the 700R4 into the 4L60E allowing use of the '88 shift linkage without modification.
*I don't believe the Oil Pressure Sending unit or Coolant Temperature Sending unit are different (resistive scale), You just need to wire them to the '88 body harness.....Oil Pressure is Dark Blue & Temp is Dark Green.

*You will need Bank 1 & Bank 2 upstream Oxygen Sensors, You can use the '99 up-pipes for this & have the exhaust connected by a exhaust shop.

*I offer bench tuning for '98-'00 Vortec PCM's.....PM me for pricing & details.

 

[jstutz]

Thank you guys for the help. I will study your responses tomorrow and try to answer any questions.

 

[dfarr67]

Easiest way to decent power is:
- conversion TBI intake.
- 454 TBI
- pass exhaust manifold to source egr
- electric fans
- don't forget your trans, likely a 700R, easier to deal with keeping old electrics or go 4L60E
- LT1 cam, clean up a little on the heads
- tune for ecu, DynamicEFI ecu, gearheads.com

 

[D60]

The 99 requires 60 psi of fuel pressure to start if you're keeping it stock with the port fuel injection.

I was able to get a '99 Escalade to start and idle at 50psi (for as accurate as the analog gauges and my eyes are) on my top end cleaner.

But yeah, that was just idling to run off the bottle. I'm sure driving performance would be dismal at 50 or even 60. clinebarger says a dead-headed pump should be 95-100 to be considered healthy.

 

[Bailey28]

99 Vortec intake will not fit on an 88 long block.. the bolt pattern is entirely different.