Author Topic: 1997-2000 3.5 SOHC to 3.8 SOHC engine swap information thread.  (Read 1044 times)


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This is an information dump regarding the engine swap I recently preformed on my 1999 Montero (3.5 SOHC, automatic)

The engine swapped into this 99 Montero is from an 04 Galant, it was originally a front-wheel-drive transverse mounted engine. Changes need to be made in order to use this engine longitudinally. I will attempt to cover these changes in the information below. This thread will evolve and this first post will be more updated as time goes.

Previous discussions on various forms of 3.8 engine swaps can be found here. While that thread is a great source of knowledge, it covers a lot of variations of engines and chassis applications which can bog you down with data. Since the 97-99 chassis is so commonly swapped, this thread is dedicated to that specific swap.

This thread will cover installing a 3.8 fwd engine into the 97-00 Montero chassis. The 3.8 engine is the same deck height, the larger displacement is achieved with a longer throw crank and different pistons. The cylinder heads on the 3.8 also have larger valves and larger bowls. Mechanically you're just doing an air displacement upgrade.

This swap was started with a 2004 3.8 engine, stripped down to just the long block, using the 3.8 cams and practically everything else from the 3.5.

Here's a list of hardware I swapped over.

-valve covers from 3.5 (3.8 had coil on plug, not this time around)
-driver side 3.5 rear cam plug, 3.8 had a cam sensor on the 'rear' of the driverside head, removed along with the flywheel, replaced with oem plug
-driver side 3.5 cam gear and timing flywheel for the 3.5 style cam sensor (passenger cam gear on the 3.8 is the same as the 3.5)
-Timing shields that bolt to the heads, no mods needed
-3.5 crank sprocket and timing flywheel
-3.5 crank and cam sensors
-timing covers from the 3.5, bank 2 needed a small notch cut in it using a dremel.
-lower intake plenum from 3.5
-fuel rail and injectors from 3.5, the injectors are lower flow rate than the 3.8, so you may need to run premium fuel, havent verified lower octane works yet but mine works on premium fuel. (15,000 miles of use later, premium yields great results)
-3.5 water pump assembly and water plumping, rear cross over tube, 1" valley tube, 2" upper return tube and thermostat housing from the 3.5
-Oil pump from 3.5, this sets the timing tensioner angle, be careful when buying new as many companies sell the wrong pump with incorrect cooler mounting orientation, i re-used my oem one since it was in spec still
-3.5 timing tensioner arm, hydro tensioner, tensioner pulley and idler pulley with spacer
-3.5 oil pan, two holes will need to be drilled in the block, its easy and will be covered with photos
-3.5 engine to trans plate and flex plate
-3.5 engine mount brackets, some bolts line up, some dont, a little drilling and the making of a small spacer should cover it.


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Re: 1997-2000 3.5 SOHC to 3.8 SOHC engine swap information thread.
« Reply #1 on: March 11, 2020, 11:29:15 PM »
Subscribed. Thanks for sharing.
Already learning.  ;D
99 Montero Winter package