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2.7 to 3.2/3.5 Swap Information

171K views 217 replies 68 participants last post by  colorado2011 
#1 ·
Here's the lowdown on what is involved in swapping your Intrepid from a 2.7 to the 3.2 or 3.5 HO engine. This also applies to the Chrysler Concorde.

Engines:
You must match your year range with your engine. If you have a 1998-2001 Intrepid/Concorde, you will need a 1998-2001 3.2 or 3.5 engine. For 2002-2004 models, only the 3.5 Magnum or 3.5 HO can be used.

Engines must be complete as possible. They need to have the starter, alternator, a/c pump, power steering pump, a good engine wiring harness, upper plenum, and motor mount brackets. Just ask for a complete "drop out" when calling a boneyard.

The engines can come out of any LH model car, which includes Chrysler 300M, LHS, or Concorde. Intrepid ES, Concorde LXI, and Intrepid R/T are also good donors.

ECU/Transmission:

The 2.7 ECU will operate a 3.2/3.5 engine without problems. The 3.2/3.5 wiring harnesses will plug right into the 2.7 car and computer.

The transmission will also bolt right up. All LH models were equipped with the 42LE. You will gain a gear ratio advantage as well, because the 2.7 vehicles had a 3.89 ratio, and the 3.2/3.5 models had a 3.66 ratio.

Parts:

Here's what you need to connect a 3.2/3.5 into a 2.7 car. Everything is pretty much the same parts wise for 1998-2004, with the exception of a few parts. The 2002-2004 models have an IAT sensor in the air intake hose, whereas the 98-01's do not.

Throttle/Cruise Cables
Air intake to throttle body pipe
Oil Cooler Lines
Power Steering tube (pump to high pressure line)
Power steering reservoir
Power steering suction tube (reservoir to pump
Power steering reservoir bracket
Transmission dipstick tube
Transmission cooler lines
Belts
Upper/Lower Radiator hoses
Heater hoses
Torque converter bolts
Radiator (2.7 does not have oil cooler, 3.2/3.5 does)

You can get all this stuff used, or new from the Dodge dealer, they are relatively cheap, except the radiator. I would purchase the radiator at a radiator specialty shop to get the best price. You can retain the original 2.7 radiator, and install an aftermarket oil cooler (hayden brand is best), but I suggest you have your original radiator cleaned and thoroughly checked for leaks or other problems.

It sounds like alot, but it is still cheaper than installing a used 2.7. The 3.2/3.5 engines do not have the notorious problems that the 2.7s do, and will last and last, if taken care of.

A/C: The 2.7 a/c lines can be re-bent and re-used, or you can get the factory 3.2/3.5 lines from the boneyard with your engine. They will bolt right in, and make for a much neater look. You could always buy them new also, if you wanted to spend an extra $200.

Exhaust: The 2.7 exhaust has to be slightly modified to work. The passenger side pipe has to be cut right behind the post-cat O2 sensor and shortened 2 1/2 inches, and re-welded back together. The hangers have to be re-positioned slightly to get them perfect.

93-97 3.5 engines: 1st generation engines are not compatible for the swap.

This is pretty much a bolt-in, plug-in swap, if you have all the correct parts.

This swap works only with a complete, used 3.2 or 3.5 engine. I suggest replacing the spark plugs, oil pan gasket, timing belt, and water pump before installing it. Its not absolutely necessary, but will save you maintenance work down the road, especially if the engine you get has over 50K miles.

If you install a 3.2, you will gain about 30HP, a 3.5HO, about 45 HP, over the 2.7. Not to mention the lack of the 2.7 problems. :rck:

Post your swap questions/pictures/results/concerns here, I will be glad to help!
 
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#3 ·
ole_pappy said:
hi iam in the process of doin a 2.7 to 3.5 swap in my 98. i was wonderin if you had to do anything to the exhaust on the drivers side as you don't mention havin to shortin it .

Nothing has to be done to the drivers side pipe. However-- you might have to bend the hanger alittle to get it to line back up, but that will depend on how well the passenger side pipe was lined up when it was cut and re-welded.
 
#5 ·
Do you guys use the 2.7 transmission or use the 3.2 trans?

I have a local yard asking $1500 for an engine/trans/ecu/harness/rad/mounts........basically anything I want fromt the engine bay. Motor has 100k and is coming out of a 98 concord. I am getting a 99 intrepid, but the engine is dead. All I basically need is an engine.
 
#10 ·
ole_pappy said:
i got my engine in ok , but when i was hookin it up i found a vacuum pipe from the intake under the throttle body n have no coresponding one on my old 2.7
The only one I can think of that is UNDER the throttle body is not a vacuum line, but a coolant line. It is a 3/8 hose, and goes over to the surge tank. The line tees off from the main heater hose line under the throttle body.
 
#13 ·
ok , i have a hose comin from the bottom of the tank and i attached it to the stell line that runs from the fron to the back of the motor and the t's. the other t has the return line from the heater on it. the steel line i am wonderin about comes out under the throttle body n ends near the fuel n return line for fuel . that steel line is smaller than the hose from the reservoir . any other ideas or some place i might find a better picture or description of the back of the 3.5 ?
 
#16 ·
ole_pappy said:
ty for the help i have one last question as i am about finished installing the engine. the motor came from a 2000 concorde and the crankposition sensorlead doesn't fit the sensor from my 98 transaxle , any ideas as to why?
Youve probably got the old style sensor in your car. Just go buy one for a 2000 and up Intrepid or Concorde and that will be the right one. Get it from the Chrysler dealer, its substantially cheaper than the old style sensor you have.
 
#18 ·
Does anyone know the estimated costs of engine swapping, and what it might cost to have a mechanic do the swap?

The most I've ever done to an engine is replace the valve cover gasket on my Shadow's 2.5...I'd be too intimidated of an engine swap.

I have a 2000 Intrepid with 187k miles on it with the infamous 2.7 Up until now it's been trouble free, in fact it still is, but I hear what sounds like an ever so slight knocking sound...my mechanic thinks it may be the camshaft bearing but without opening it up we don't know.

You can only hear it if the car is stopped and the HVAC and radio are off...You can't hear it over even talking...it's barely noticeable but it is there.

When I was at the junkyard yesterday I came across a white Intrepid that had no bumper or rear wheel but still ran, and I got to experience the "2.7 knock" first hand. Broke my heart to see the poor car dying...

Anyway...

With the miles it has I was thinking it might be more economical to save up and drop a gently used 3.5 in there rather than dumping a ton of money into the 2.7.

I was just wondering if anyone has experience price-related...also do you need a new fuel pump or is it universal for all engines?

Thanks!
 
#19 ·
If you have a mechanic shop do it, count on a range of $2700-$3500, depending on how familiar they are with the conversion. As for the fuel pump, its universal, will work with all engines.
 
#25 ·
CHEVYLUV80 said:
HI, I have a question. How come the first gen. 3.5 won't work? Is it the OBD1/OBD2 computer stuff or the trans bolt pattern. I can get my hands on a 1994 intrepid with a 3.5 24 valve real cheap.
Several reasons. There are so many differences between the 1st and second gen 3.5's that it makes swapping them into the second gens counterproductive.

Electronics, wiring, exhaust, oil pan, and engine mounts just for starters. To add, the 1st gen 3.5 has less HP than a 2.7, whereas a second gen has 50-60HP more than the 2.7. You would basically have twice the work in the conversion as a second gen 3.5 would, and much less power.

Swapping in a second gen 3.5 or 3.2 is pretty much parts swapping and plug and play. Just make sure you match the year ranges (98-01 to 98-01, and 02-04 to 02-04).
 
#26 ·
Hi,
I recently completed the 2.7 to 3.5 H.O. shuffle. Everything was pretty straight forward and I incurred no issues in the installation due to all of the detailed posts in the Intrepid forum. The donor engine came out of a 1999 LHS. The engine was installed into a 1999 Concorde. Swapped the motor and transmission. The engine turned over and started with only a 30 second rough idle. The idle jumped to around 2500 RPM. This lasted for approx. 3 to 5 minutes. The idle now rests at 1500 to 1600 RPM and 1000 RPM in gear. I recently completed all of the exhaust work and have no vacuum leaks. (Sprayed starting fluid all around the manifold) I drove the vehicle in the city, stop and go for about 30 minutes and took the vehicle on the highway for a 50 mile round trip thinking surely the computer would remap itself. NOPE! Still idles @
1500 to 1600 RPM. No Check engine light. I've tried to blip the throttle wide open. The computer takes over around 3000 RPM and engages the rev limiter. I did install a new throttle position sensor. I unplugged it at idle and had no change in idle speed. This was the only check engine light I incurred, because I caused it. Any ideas you have would be greatly appreciated. I e-mailed Dan but have received no reply. With so many swaps that have been completed I was hoping someone has seen this one.
Thanks!
 
#72 ·
YOU :rck:
Now where did u go to get it done. I own a Intrepid R/t but some idiot hit me on my right fendor kinda hard. And alot of body shops tell me its gonna b too expensive. I can easily get my hands on another intrepid for $700 easy. So i need help doin the swap. Can u help?
 
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