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Replacing AMC 304 with AMC 360 in 78 Pacer

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mantonas View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mantonas Quote  Post ReplyReply Direct Link To This Post Topic: Replacing AMC 304 with AMC 360 in 78 Pacer
    Posted: Feb/10/2018 at 6:14pm
As the subject says, I have a 78 Pacer with a factory 304 V8 engine. The original engine was already blown when I bought it. I know that I'm going to have to transfer some Pacer-specific stuff from the old engine onto the replacement, and I think I have a handle on that stuff. But today as I was thinking about the project, I started wondering whether I was going to have any balancing issues with the torque converter and flywheel. I bought a 360 to install on craigslist and it has a flywheel on it. I haven't checked the number of teeth to make sure it matches the one in the Pacer; assuming it does, will I have any balancing compatibility issues if I stick the 360 with its flywheel into the Pacer using the Pacer's torque converter? FYI, according to the guy who sold me the 360 engine, it came out of an 80s Grand Wagoneer.
1972 AMC Javelin SST
1973 AMC Ambassador 401
1975 AMC Pacer D/L
1976 AMC Pacer X
1976 AMC Matador sedan
1978 AMC Pacer V8 coupe
1987 Jeep Grand Wagoneer
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Post Options Post Options   Thanks (0) Thanks(0)   Quote wantajav Quote  Post ReplyReply Direct Link To This Post Posted: Feb/10/2018 at 6:35pm
What plate is on the 360 now?..... "Flywheel"....

If it is thick/heavy steel donut that is a manual transmission pressure plate.

The flex plate for an automatic is thin, looks like


Its $28 bucks - you need a 360 one.

I think you need to remove a pilot bushing from the crankshaft if it was a manual transmission on the Jeep.

Reuse your 304 exhaust manifolds on the 360. 


Edited by wantajav - Feb/10/2018 at 7:00pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote one bad rambler Quote  Post ReplyReply Direct Link To This Post Posted: Feb/10/2018 at 9:33pm
The word Flywheel has been mis taught forever ..just like a sway bar ...it`s a stabilizer bar....Confirm that your torque convertor fits in your crank and all 4 bolts line up with the holes in the flex plate
68 AMX 390 4 Speed,68 American,64 American 2 Door Wagon Altered Wheelbase,78 Concord Build 360,727,8.8
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mantonas View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mantonas Quote  Post ReplyReply Direct Link To This Post Posted: Feb/10/2018 at 10:36pm
I can't go look at the engine right now because it's in a storage unit, but I'm pretty sure what it has on it is like what's in the link you sent. Most of my V8 engine experience is with mopars, and they have a flexplate bolted to the crankshaft that bolts directly to the torque converter. If the engine was externally balanced, then you had to use the right harmonic balancer on the front of the engine, and if I'm not mistaken the torque converter also had to be one that was for an externally balanced engine. The round plate on the back of the AMC engine that we're talking about, which I always thought was called a flywheel, is integral with the torque converter on mopars. That's why I'm asking this question, to find out if AMCs had this balance issue and if so what to do about it.
1972 AMC Javelin SST
1973 AMC Ambassador 401
1975 AMC Pacer D/L
1976 AMC Pacer X
1976 AMC Matador sedan
1978 AMC Pacer V8 coupe
1987 Jeep Grand Wagoneer
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mantonas Quote  Post ReplyReply Direct Link To This Post Posted: Feb/10/2018 at 10:44pm
I think the exhaust manifolds on the 360 will work, because if I am not mistaken they are the same for Pacers and Grand Wagoneers. I might have to swap the oil pan. I know for sure that I am going to have to swap the timing cover, because it is Pacer-specific. That actually concerns me a lot, and I was going to start a separate post about it, because the timing cover contains the oil pump, and if the 304 engine is blown, it might have been due to low oil pressure, which means I should rebuild the pump, which I think involves machining the inside of the timing cover and shimming the moving parts of the pump.
1972 AMC Javelin SST
1973 AMC Ambassador 401
1975 AMC Pacer D/L
1976 AMC Pacer X
1976 AMC Matador sedan
1978 AMC Pacer V8 coupe
1987 Jeep Grand Wagoneer
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 401jim Quote  Post ReplyReply Direct Link To This Post Posted: Feb/11/2018 at 6:00am
304 and 360 front covers are the same and you will not have to exchange them. The flywheel that came with the 360 will have to be used along with the harmonic balancer from the 360. both engines have specific external weights and can not be used on a different cubic inch engines. hope this helps you.....Jim
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 401MATCOUPE Quote  Post ReplyReply Direct Link To This Post Posted: Feb/11/2018 at 6:17am
I have done this swap before, 304 to 401, since the 304 uses a 998 trans and 401 normally use the 727....you would need to shorten the driveshaft, but he 998 will certainly bolt right up to the 360.  In mid/late 80 Wagoneers (GW) went to a different flex plate.....personally if you have it apart put a new one in.

Pacer exhaust manifolds are unique and the GW one will not fit, just reuse the ones you have.

Pacer V-8 timing cover is not different BUT the oil filter adapter and gasket are completely different, ao you need the special gasket and adapter need to be swapped.....the GW oil filter adapter will drive the filter right into the rack and pinion steering gear.  Use all the Pacer accessories and bracket up front and you should have no other issues that I remember.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mantonas Quote  Post ReplyReply Direct Link To This Post Posted: Feb/11/2018 at 7:35am
That's good news about the timing cover, I just need to swap the oil filter adapter. Now I guess I just need to worry about whether the torque converter and flex plate will match (i.e., fit together and bolt up).
1972 AMC Javelin SST
1973 AMC Ambassador 401
1975 AMC Pacer D/L
1976 AMC Pacer X
1976 AMC Matador sedan
1978 AMC Pacer V8 coupe
1987 Jeep Grand Wagoneer
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Post Options Post Options   Thanks (0) Thanks(0)   Quote harry401 Quote  Post ReplyReply Direct Link To This Post Posted: Feb/11/2018 at 7:48am
The 304 likely has a lockup converter and trans I have a 998 bolted to a 360 no lock up. If your 998 trans is marginal I would get it rebuilt before throwing a 360 in front of it
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 401MATCOUPE Quote  Post ReplyReply Direct Link To This Post Posted: Feb/11/2018 at 9:46am
If you are going to use your original trans, then the torque converter is not and issue to bolt up to the 360 Flax Plate.....harry401 is giving good advise on the trans condition, if it is questional then rebuild it before you put is back in the upper trans bolts are difficult to get to......when I swapped the 401 in the car I did , I put engine and trans in as one piece from top, saved a lots of grief.
Ross K. Peterson
68X,GoPac,343,AT,52A(1stCar)
68X,GoPac,390,4sp,52A
69X,GoPac,390,4sp,64A
70X,GoPac,390,4sp,87A,8
70X,GoPac,390,4sp,BBO,8
70 Jav SST,390,AT,BSO
74MatX,401,AT,Prototype
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