There's plenty of info on doing XJ 2.8L to 3.4L swaps out there but also a few misconceptions and missing pieces to the puzzle that we had to figure out along the way. This page is to help point ya in the right direction and answer the questions the other sites didn't cover. Be sure to look through ALL of the links immediately below! They'll answer MANY of your questions and put the rest of this article into context.
3.4L engine, performance info & engine swap links
Although not intended to be a 'step by step' guide, this page should help answer a few of the questions specifically related to doing this swap in your 2.8L Jeep Cherokee that are not covered in detail in the other write ups. When you're at their sites, ya gotta thank those who took the time to get the info out... it sure saved my arse along the way!
First off... get some masking tape and a permanent magic marker. It'll save you MUCH grief later trying to decipher where each of the zillion and one vacuum hoses go. Yeah, a lot of them can be eliminated... after you get your swapped motor up & running. A link for the vacuum hose schematic is listed below with the photos of the swap.
We used a 1995 Firebird / Camaro engine that came with the SFI injection system. Not having the time or expertise to splice in a GM computer to run the thing... we ditched that assembly and swapped over the 2.8L manifold & carb. Dang shame as the injection set up looked sweet on top of that motor! The new motor runs great and makes a 2.8L engine seem like a lawn mower engine by comparison in performance!
|AaronXJ on JU
contributes this info: "...4cyl AW4, AX5 trannies have
a 60* bellhousing. It is a very stout tranny swap, in terms of long term
reliability that will allow you to run a 231 TC."
This means that if your old 2.8L's transmission is also shot... you can swap it out when you swap in the 3.4L using a 4 cylinder XJ AW4. You'll be able to run the AW4's NP231 transfer case as well but if you pay attention to spline counts your old 207 or 208 will work on 21 spline trannies...
Here is a list of what was swapped from the 2.8L over to the 3.4L. After 5 months of driving we can pretty much call this swap complete but this page will be modified from time to time as we tinker with the XJ.
parts to keep for swap onto 3.4L
2.8L flywheel / flexplate - MUST be 'neutrally balanced at a machine shop to work with the 3.4L!
2.8L harmonic balancer
2.8L Intake & carb (Unless you go the fuel injection route... in which case yer on yer own!)
2.8L oil filter mount
2.8L timing cover & oil pan
2.8L Accessories and brackets (power steering, a.c., alternator...)
2.8L exhaust manifolds (3.4L manifolds could be modified w/ a little work.)
2.8L motor mounts
2.8L valve covers (Or fab a mount to hold throttle linkage & return spring w/ 3.4L covers as we did.)
parts to reuse and/or modify
3.4L long block (naturally...)
3.4L oil pump & sump (* see picture notes)
3.4L valve covers work but you'll have to fab up a mount for the throttle linkage and return spring for the passenger side cover plus swing the oil filler tube around on the driver side.
3.4L reusable exhaust heat shield manifold gaskets
3.4L reusable one piece oil pan gasket (You must trim off front lip for 2.8L timing cover.)
NEW parts you'll need:
|Major Parts For Manual Transmission
Not bad for $100 & able to drive it outta the seller's yard.
A few scrapes & dings but in dang good shape!
Exploder wheels w/ new 'WalMart' tires...
Hitch is someone's idea of a joke...
While it had a bracket for the frame - it's bolted to the rear bumper with....
An old exhaust clamp. Definitely not Class III!
$450 later, we had a 1995 Camaro/Firebird 3.4L SFI engine shipped to a local boneyard through the used parts exchange.
Front view of serpentine pully set up.
Boneyard motors arrive without any accessories.
1995 Camaro/Firebird 3.4L SFI engine.
Engine was from automatic CamBird. You cannot reuse the 3.4L CamBird flexplate/flywheel for the swap.
Notice also that this motor does NOT have a distributor. You must reuse the 2.8L distributor.
1995 Camaro/Firebird 3.4L SFI engine.
Externally identical to 2.8L engine w/ exception that the 3.4L does NOT have an opening for a cam driven fuel pump. You must use an external low pressure electric pump.
1995 Camaro/Firebird 3.4L SFI engine.
Exhaust manifolds appear to be dimensionally the same but have various ports, doo dads & shields that interfere w/ the swap. Just reuse the 2.8L manifolds but with the 3.4L reusable heat shield gaskets.
1995 Camaro/Firebird 3.4L SFI engine.
Anyone need a 3.4L fuel injection system... complete? It sure looked bitchin' sittin on this motor but it had to go to simplify the project.
These are the left over parts from the swap... so how did I end up having to go buy bolts with all this left over???
3.4L serpentine timing cover.
Pump cavity is designed ONLY for REVERSE rotation water pump!
Note crankshaft position sensor located at crank seal opening.
2.8L standard rotation timing cover.
Cavity is designed ONLY for STANDARD rotation water pump!
Upper pickup tube is 3.4L's pump & pickup which stayed on the 3.4L block.
Lower unit (in hand) is smaller 2.8L pump & pickup tube.
Timing cover gasket set for 2.8L... ya gotta get the 2.8L set in order to reuse the 2.8L timing cover. Be sure to install that new dampener seal too!
2.8L flywheel showing the weight that must be machined down when flywheel is neutrally balanced. You MUST have this done! Do NOT attempt to use old flywheel w/o doing this! Have friction side resurfaced while it's at the machine shop. Total cost for was $90 for machine work.
|Sorry but no pic of the machined
flywheel after I picked it up... I coulda swore I took one but maybe the dog
About 75% of the weight (shown at left) was machined off and reliefs were drilled to neutrally balance the flywheel.
While they had it & since a new clutch assembly was going in we had them resurface the friction side too.
One little joy was taking the clutch parts with me to make sure I got the right part... then returning to exchange the clutch set after finding out that previous repairs had left parts from two different size clutch sets inside. (Small disc w/ larger pressure plate from different year XJ's.)
3.4L reusable one piece gasket (blue, folded up onto top of crank snout) and 2.8L oil pan (lower, slanted beneath timing chain).
You must cut off the exposed area of the 3.4L gasket to allow usage of 2.8L timing cover.
Mark old one piece gasket w/ sharp blade. You will have to remove the gasket and CUT the one piece gasket's internal METAL strip as it will protrude beyond the sealing area and prevent the timing cover/oil pan from seating.
ALL of the exposed blue one piece gasket has been cut away and the pan reinstalled. Here is lower timing cover gasket from 2.8L timing cover gasket set.
|As a side note... the 3.4L
CamBird oil pan was VERY similar in shape & size to the 2.8L pan we swapped
over... This leads me to think that if someone was energetic enough to splice
in a computer to run the fuel injection system they could
***PROBABLY*** keep the serpentine & fuelie setup on
the 3.4L intact with little more than a motor mount lift, like in a
Now, I dunno if this idea will actually work! I didn't do it! But it does look possible due to the similar nature of the oil sumps. Hood clearance might be an issue, but then ya'd have an excuse to buy one of those nice cowl induction hoods, right?
I swapped in a new filter to the 2.8L's Rochester but be sure to put a generic inline fuel filter at the tank (and before the fuel pump) like this!
Be sure to replace ALL rubber gas lines while yer at it!
Picture of the mounted external electric fuel pump from AutoZone. I routed the power & ground wire through two small holes drilled in the rubber grommet for the fuel tank sender wires and ran them with the OEM wiring harness to the front.
Don't leave any excess wire hanging!
A rubber grommet for leads to fuel tank sending unit is located under a metal bracket beneath rear seat. There was some duct tape holding the wires outta the way so I used a little when reassembling things and fed pump leads along existing wire harness up to the front driver side kick panel.
|Since I lost the picture that
was gonna go here...
Here's a link to the .pdf instructions for a
Mallory LOW PRESSURE Fuel Pump!
(This link will open in a new window leaving this one intact.)
Please not that this pump will NOT work with fuel injection! This pump is intended for CARBURETED engines!
The 3.4L doesn't have a mounting boss or any means to mount a mechanical fuel pump but that didn't stop me from using the existing fuel hose and hardline routing.
I cut off the metal fuel line where it would normally attach to the 2.8L mechanical fuel pump then bent the line upward toward the driver side fender well. I then ran a new gas line over to it from the stock line from the tank that is on the driver side fenderwell.
2.8L Rochester carb & manifold atop their new home! Carb was reinstalled 'as is' and distributor timing was guessed at but with a little fiddling fired right up.
Worked fine but I wish we would have had the coinage to pick up that Weber from the JU 'For Sale' board... and that Edelbrock cam & lifter set on eBay... and the Edelbrock intake on eBay...
Here is a link to a schematic for all those vacuum hoses!
Uh-oh... '710 cap' is in the way!
It's easier to keep the 2.8L valve covers since they have the bracketry in place and everything fits to match the air cleaner and throttle cable... unlike the 3.4L valve covers that I kept. These two issues could have been avoided if I'd just swapped the 2.8L valve covers over with the throttle mounting bracket & the '710 Cap' (oil filler cap) tube that is angled the wrong way for the XJ's air cleaner neck.
I just removed the bolt holding the '710 Cap' tube & rotated it 180*. I'll add a strip of metal from the tube's bolt hole to the bracket hole on the 3.4L valve cover.
(And in case yer wondering why I didn't just reuse the 2.8L valve covers... I'm a cheap SOB and the the 3.4L valve covers really looked nicer. They are slightly more square in appearance and the gaskets on the 3.4L looked darn near new so I reused 'em!)
3.4L sitting in it's new home now disguised as a paltry 2.8L.
It looks almost naked without that big injection system sitting on top of it.
From stripped down to dressed up... Here she is all covered up with the accessories from the 2.8L.
View looking down from passenger side of motor to where I mounted the battery ground wire(s). Note that I ran one wire from the battery ground terminal to this point on the block then ran a seperate ground cable from the block to an existing hole to provide a WELL GROUNDED point in the frame. This is in addition to the XJ's puny ground strap that was reattached to the back of the head & firewall.
Poor grounds are a source of MANY electrical problems! Check out Craig's EXCELLENT tech area for more tips on this! (Opens in new window.)
The 3.4L & 2.8L both take the same oil filter (Fram 3387A) but the mounts are slightly different. Use either one but the 3.4L oil filter mount using a different thread size oil pressure sending unit so you'll need an adapter bushing from the hardware store to swap in your 2.8L oil pressure sending unit.
I just swapped the old 2.8L mount over to the 3.4L block but either way be sure to replace the o-ring!
At your oil filter, install a tee and add a low pressure shut off switch like the Holly #12-810 one shown above to kill power to the fuel pump in case of vehicle rollover etc where oil pressure is lost! This will shut down the fuel pump when engine's oil pressure drops below a preset value, around 10 pounds depending on switch. Here's a link to the Mallory electric fuel pump installation instructions in .pdf format that shows how to wire one up and install the oil pump pressure switch.
A picture of the installed low oil pressure / fuel pump shut off switch was gonna go here... Since the XJ is long gone it ain't likely that I'll ever get a pic of that installed tee and low pressure switch posted, eh?
So your choice... look at the babe - or at a blank space?
Be sure to install a new pressure sending unit for the guage. You'll have to futz around with the 'tee' a bit to get the combo situated to suit ya and have everything up outta the way.
Somewhere in the XJ's past the entire front end was pulled & a few parts were missing... like the lower radiator bracket I made from a strip of 1/8" steel with two holes drilled into it. The strap's only purpose is to keep the radiator from swinging front to rear... (upper bracket holds radiator's weight).
View from beneath looking up at ground straps, alternator & timing cover.
Yeah, I was bored. Maybe I fell asleep and the camera went off... I dunno but if I had to spend all dang day under this thing looking at 2 year old layers of caked on grease then so are you!
This dummy-drive / 'plug' used to drive the oil pump was removed from the 3.4L engine. It's sole purpose is to drive the oil pump and plug the hole where a distributor goes... You have to remove it and swap in your 2.8L distributor. It's fairly easy but the o-ring will probably make it difficult to extract at first but trust me, after ya remove the hold down bolt and bracket, it will pop right out of there... eventually. (Ya might have to wiggle it clockwise/counter clockwise or even use a socket to turn the engine a bit to get it free but it'll pop right out when it's ready.)
Other than the squared off 3.4L valve covers & being painted black... nothing at all indicates there's more than meets the eye.
| Update 07-2006: This XJ has been long traded off by my son
but was still doing great the last time I saw it tooling around town in mid
Hydro clutch slave cylinder died about 2 months after project's completion and was a royal pain in the arse to replace on the V-6 XJ/SJ! This was primarily due to not having the right extension and laying in a wet, cold drainage ditch trying to replace it... Best advice I can give ya? Replace the clutch master & slave cylinders PLUS the line while the motor is out!
Link to Budget Lift also done on this XJ.
Overall, the swap went MUCH easier than I expected even
with having to do it outside, getting rained out, swattin' MOSQUITOS!, and not
knowing what the heck I wuzz doin'...
THANKS! to all who contributed knowledge, help, tips & bug spray.
Thanks also to my ex-wife who put up with my son
& I doing this in her driveway...
which is now covered with enough oil to put OPEC outta business...
If you have pics of your own repairs or can suggest other methods - please contribute your ideas (and pictures) to this article!
November 11, 2006