International Full Size Jeep Association
Home Forums Reader's Rigs Tech Library Trail Stories FSJ-List
International Full Size Jeep Association  

Go Back   International Full Size Jeep Association > Tire Kickin' > General FSJ Tech

Thread Tools Search this Thread Display Modes
Old 02-26-2020, 08:37 AM
johnnywaka johnnywaka is offline
230 Tornado
Join Date: Sep 22, 2019
Location: Kentucky
Posts: 3
Engine replacement question 90 gw and 78 wag

Hey all. I have a 78 wag with no engine, a th400 and qt. It had a 360 in it.

I also have a rusty 90 gw with a 360 and tf727. I am planning on yanking the 360 from that and swapping it into the 78.

My question: What are all the extra parts I need to get? I think I need to get a flexplate for 78 th400 and that's it.

also, I'm planning on redoing my gaskets on the 360 while I've got it out. Anything else you all would recommend doing before I drop it in?

Rusty 1990 GW. stock rig
Reply With Quote
Old 02-26-2020, 09:45 AM
babywag's Avatar
babywag babywag is offline
out of order
Join Date: Jun 08, 2005
Location: Land of froot loops and cukcoo-nuts, CA
Posts: 9,659
There are some small differences...

flexplate and crank spacer ring needed for th400
the starter is different 78 vs 90
driver side manifold for 78 with passenger drop axle is different
power steering gearbox and pump are probably flare fittings on 78
90 is metric o-ring so you'll need adapter fittings or custom hoses with ends changed for 78? Or you could use an earlier ps pump fitting to change ps pump to flare fitting.

If you search using google or bing with "" specified it'll bring up previous thread discussions on all this.
Reply With Quote
Old 02-26-2020, 09:56 AM
fulsizjeep's Avatar
fulsizjeep fulsizjeep is offline
Señor Jackhead
Join Date: Aug 21, 2002
Location: Jubilee Jeeps.SWCO
Posts: 22,362
Ditto what Tony said. Shouldn't be hard to source a 70s LH exhaust manifold. AMC Motorcraft starters are still available at most parts stores or online.

The "sizing ring" is available here:
Ran when parked.
88 GW, 401/727/208, 5" lift, D44s/4.10s/locked up, 35s with a few Evil Twin & TT's Fabworks mods
76 401 Wag, 77 401 Wag, 77 401 J20
Reply With Quote
Old 02-26-2020, 10:21 AM
Full Size Jeeper's Avatar
Full Size Jeeper Full Size Jeeper is offline
304 AMC
Join Date: Jul 20, 2014
Location: Mandeville Louisiana
Posts: 2,144
I would consider a new timing set, replace the valve stem seals and rework the oil pump housing. Also if the engine can still be turned over, I would run a compression test.
1978 Wagoneer

401/turbo 400 trans. Quadra-Trac BW1339 (with Low) 4" Rusty's lift with 31" Summit Mud Dawgs

Fuel Tank, Red Holley Fuel Pump, Razor Grill (profile pic out dated), Rebuilt steering box
Reply With Quote
Old 02-26-2020, 07:59 PM
Bob Barry Bob Barry is offline
Jeep Doctor
Join Date: Apr 09, 2000
Location: Providence, RI
Posts: 8,268
There will be a lot of minor things that will be annoying, but you should be aware of them:

* The '90 will have a metric-thread oil-filter; you can swap in the nipple from the older engine to use standard-thread filters.
* The outer exhaust-port bolt-holes are 5/16", not 3/8" like your '78
* The PCV valve on the '90 will be in-line and connect to a 90' pipe on the back of the intake, unlike the PCV that fits into a grommet on the intake on the '78
* The 2150 carburetor on the '90 will have an altitude-compensator, and perhaps different hookups than your '78.
* The oil-pan drain bolt will be in a different position, but I don't think it will be in the way of anything on your '78
* The A/C compressor bracket on the '90 will be for a Sanden compressor rather than a York. You may also have a different alternator bracket, but everything should swap over from one to the other, EXCEPT that the pivot-bolt on the '78 is larger, I believe, so that may not swap directly over. The '91 did use the same type alternator, however, unlike the '77 and earlier, so you can keep the brackets from the '90.
* You'll want to use the sending-units from the '78, as the '90 used different gauges, and I believe different senders.

The critical thing that others mentioned is the spacer sleeve for the smaller snout on the TH400 torque-converter.
Reply With Quote

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Engine Question hannaganscr General FSJ Discussion 23 01-30-2014 09:51 AM
HDC CTO (???) Gil General FSJ Tech 46 03-31-2010 10:23 PM
Engine R & R write up SFFSJ General FSJ Tech 0 04-16-2003 05:03 AM
Help please Dan G General FSJ Tech 36 09-02-2002 08:47 AM

All times are GMT -6. The time now is 04:11 AM.

Powered by vBulletin Version 3.5.4
Copyright ©2000 - 2020, Jelsoft Enterprises Ltd.
corner corner