With 100's of different potential homes for the 4200 this will be a general guide.
The 4200 only came with the a 4l60E transmission from GM. So using that combination is the path of least resistance.
The best way to do a 4200 swap is to buy a running vehicle - one that came to an unplanned stop is perfect. This way you have all the parts needed and you can sawsall your way in.
The trailblazer/envoys came with a pretty good rear suspension that is mounted to a cradle - so its a potential swap.
Before disturbing the engine - do a oil flush on it - I use a qt. of kerosene - let it run for 10 - 15 min. drain it. Then put the drain plug in - pour another qt. of kerosene in, and let it sit for 10 mins, then drain the residuals out of the pan (use a different catch can so you can examine the drainings) - you will be surprise what comes out.
This will get the oil pan clean in case you need to do something with it.
Engine mounts
Engine mounts are either reuse all/part of the stock mounts and adapt the frame side to its new home, OR custom fab new mounts.
Exhaust system (passenger side)
The exhaust manifold is a fairly good design part and with a 3" exhaust behind it works well. Tom Langdon has done split exhaust manifolds for the 4200. If you have room and running a single pipe the stock muffler is the quietest one to use with the 4200.
Oil Pan
The stock pan is front sump pan that can cause interference problems - look in the 4200 parts posting for a rear sump pan if its needed. Alternative - modify the stock pan or whatever is in the way.
Drive by wire throttle
If you are going to keep the GM PCM then you MUST keep the drive by wire throttle plate and gas pedal.
Even if you build a custom intake manifold and run the GM PCM - you must use the drive by wire throttle plate and electric gas pedal.
The PCM will shut down and go into emergency mode if it does not see the wire throttle plate and electric gas pedal. IT will not allow the engine to run. An early attempt was made to eliminate it by Westers Garage and it failed.
The alternative is to run megasquirt - then you have full control over the engine an can run a cable throttle. But you have to be comfortable with wiring and tuning a EFI system.
GM PCM and harness
Look in the 4200 part post for Lime-swap, Jeremy does harness strips and PCM unlocks.
Transmissions
The 4L60E with a shift kit and some PCM tuning is not a bad choice if you want to run an automatic. This uses a TH350 type output slip yoke.
If you have a different transmission that bolted to a 194/292 or sbc then there is an adapter plate to allow these to bolt up - look in the 4200 parts posting. You will need a t/c spacer also - even if you decide to do a hack install and use a BOP trans and redrill the mount pattern.
When GM design the LS and atlas they shortened the crankshaft bolt flange stick out distance.
Manual transmission
MT flywheels are available - see the other posts (July 2020)
.
The bellhousing from a 2800/3500 atlas can be used to bolt up a trans out of a supra that is strong enough. Ask Lime-swap.
Fuel supply
The 04 up engines used a returnless fuel system.
2 choices - modify the firewall side of the fuel rail to add weld in block with a 1/4" NPT hole for a return line to an aftermarket regulator or run a close coupled (mounted within 12" of the fuel rail) external aftermarket regulator with a return line.
In either case you will need a high pressure (58 PSI for GM PCM systems - do not reference the fuel pressure regulator (FPR) to the intake manifold) fuel pump and regulator. For megasquirt - you can reference the FPR to the intake manifold and set the base fuel pressure to 43PSI.
I recommend where possible to run a pump in tank system as it cuts the pump noise out.
Several companies make adapters to convert the stock fuel rail inlet to a AN-6 male which allow use of aftermarket braided line for the fuel system.
Vehicle electrical connections
- gas pedal - if using the GM PCM
- constant +12V
- switch +12 V
- brake switch
- cruise control inputs to the PCM (if desired)
- electrical connection to the EFI fuel pump.
- engine OBD2 scanner plug
- check engine light
- ground
Gages
You can adapt either electrical or mechanical gages to the engine.
A/C delete
In some installations the stock AC compressor interferes with hard spots (e.g. frame) - it can be deleted along with an idler pulley and run a shorter belt.
Cooling
The coolant inlet is on the driver side of the engine.
You will need to run an electric cooling fan as the water pump is not on engine centerline.
Heater
The heater connections can be block off.
Last edited by efi-diy; 11/06/20 09:09 PM.
