Cougar Discuss all years of the Mercury Cougar here...

5.8 Swap?

Old 02-07-2009, 01:44 PM
Junior Member
Thread Starter
Join Date: Dec 2008
Location: United States
Posts: 16

Anybody ever heard of a 5.8 swap in 94 xr-7. Found one for 200 bucks out of a lightning. Just wondering how it would fit if even possible. Still a small block so i don''t figure it''s to much bigger just wondering on mounts and tranny. Would I still be able to use my t-5 5 speed ? Thanks any help would be appreciated.
Old 02-08-2009, 07:23 PM
Senior Member
Join Date: Oct 2008
Location: United States
Posts: 1,361

cougars had options for a 302 and the 351 is the same block. it''s definitely possible. the transmission may need a stronger clutch though. I don''t think there''s any problem mounting the two together, but the transmission may not be strong enough for the 351 if it was originally on a v6. since it''s a manual, maybe just a stronger clutch plate and no popping the clutch would work. It may do fine without any upgrades, but be prepared to get a new clutch plate if the old one burns up.
Old 02-14-2009, 10:02 PM
Senior Member
Join Date: Nov 2008
Location: United States
Posts: 232

Did this on an 89.. Not an easy swap! First thing to keep in mind, the 351 is an inch wider, 3/4" taller and about 200 lbs heavier than a 3.8, although not quite as wide a a 4.6 it is still heavier and taller.

You will need a double hump oil pan found on Older Crown Vics with the 351.. It has to be a 351 pan as it is wider than a 302..You''''ll need the timing cover, accessory brackets, most of the accessories, water pump, motor mounts, starter,and exhaust manifolds from a 91-93 T-Bird or Cougar with a 302.... You''''ll also need the power steering lines and A/C lines... A front spring upgrade will also be in order.. Might as well plan on some custom exhaust too (at least the y pipe)

You;ll need a hood with a scoop... Even with custom mounts and the sub frame shimmed a half inch from the body you''''ll need a min of a 2.5" increase in hood clearance. Most of the clearance problem was at the rear of the hood, but the power steering pump sticks up there pretty good too.. (alot of the after market hoods we looked at had a brace across the back that was in the way so we ended up modding a fiberglass hood)..

The upper intake from a 302 explorer would probably be the best bet short of a custom intake or custom motor mounts and beating the hell out of the oil pan...We used the intakes like was on the lightning but it required the custom motor mounts and beating of the pan... Since building a 395 stroker (Crank wouldn;t clear the bashed oil pan D''''OAH) we ordered and intake from Probe industries which is basically a 4bbl intake with fuel injector bungs welded into it.. It also came with an elbow adapter that was supposed to fit however it was an inch taller than they let on.. I''''m currently making my own adapter to mount the throttle body on there..

You''''ll also need the wiring and computer for the v8, and an upgraded fuel pump is a very good idea...

THe exhaust manifolds I mentioned earlier will have to be modified as well, the engine is wider so they have to be bent inwards a tad to clear the frame and steering...(webolted them to a junk head and used a torch and hydraulic press, fit like a glove!)I have found some cast iron manifolds that I think could be usable but as far as headers nothing real great...

The stock radiator won''''t keep it cool... The stock v8 radiator for any of these cars will not keep it cool (the factory 302 cars barely stayed cool) Griffen radiator makes one that''''ll do the trick but it isn;t cheap... An upgraded electric fan is a must for summer driving with teh A/C

The T5 will work buttoo much"spirited driving" and it won;t last too long... The 4.6bell housing is different as well, possibly the input shaft..You''''ll have to have themanual flywheel for the 351.. If you opt for an automatic it''''ll have to be one from behind a 302, 351, 3.8, or 4.2.... IF you use the older AOD no more is needed to deal with electronics... IF you use a 4R70w/AODE then you''''ll have to have a computer and harness that can control that with the engine. (Pickup 93-96or 94-95 Mustang)

The biggest obstacle in the whole mess was the additional height of the 351... Side to side and front to back was fine...

An easier swap may be to find a 5.4 with the intake from a van... Very low clearance and from what I have heard will fit under the stock hood on the 96 and newer cars (they had a notch in the hood for the throttle body, I imagine the 94 hood coudl be massaged to work) Everything else is supposed to pretty much match up to the 4.6 stuff... Other thana computer and harness upgrade since the 5.4 used coil over plug ignition instead of coil packs and wires...

Unfortunetly you''re probably not gonna find a 5.4 forreal cheapyet, and probably less likely to find the proper one from a van... THen again once in a while you get lucky... Been watching for one of these for a few years to perk up my 96 Grand Marquis...Edited by: maxfax3
Related Topics
Thread Starter
Last Post
Grand Marquis
02-17-2008 02:20 AM
09-05-2007 12:44 AM
08-18-2007 01:01 AM
Grand Marquis
05-19-2007 08:54 PM
05-12-2006 12:35 PM

Thread Tools
Search this Thread
Quick Reply: 5.8 Swap?

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to and affiliated sites.