Engine build different?

[rearview]

I read that 4.o Mj's are MX but mine is 712m16.

 

It is a pureblood renix that only saw a tow truck when I lost the clutch slave 50 miles from home. The slave was changed at 305,000 and the clutch itself was still a good clutch.

 

I bought this truck new in Feb of 88 and ran it to 320,000 when I heard a slight rod knock. Not a tappet but a rod. Sat for 4 years, put a battery in her and she fired up on the second start up attempt. Rod noise was louder so she is in the garage getting stripped down for a trip to the machine shop.

 

I was amazed that there was no ridge at all on the cylinder wall.

 

Anyone know the deal with an M and not an MX on the build code?

[jimoshel]

Standard transmission vehicles can be operated with out a clutch in emergencies. First start the engine and let it warm up. Turn it off. Place transmission in lowest gear. Start truck. Once the truck is moving you can shift gears by co=ordinating throttle and gear shift. The big rigs only use the clutch when stopping and starting. Not after the rig is in motion.

[HOrnbrod]

^^  Don't know why Jim posted the above in this thread.   :hmm:

 

Anyhow, the engine code MX = 242 MPI (4.0L MPFI, 86-01, Jeep ONLY) . Engine code M = 304 2 bbl Low Compression (71-74, Jeep ONLY). So unless you have a carbed 304 something is way wrong. Here's the complete list of AMC engine codes:

 

1968-2001:  Someone at AMC decided to simplify things, or maybe the U.S.
Government decided for them since engines  now had to be qualified for emissions by
type and size? In any case, all models used the same codes for the same engines.  
Some codes were used for more than one engine. Year ranges are given for code use.  
VIN and engine code numbers are different! This can be confusing. The 4.0 has an
engine code of MX, but there are three di fferent VIN codes (M, L, S). The earliest
VIN code usually matches the engine code, later versions of the same engine may
have different VIN codes but engine  code usually remains the same.

 

A- 258 1 bbl (71-79)  
B- 258 1 bbl Low Compression (71-74, Jeep ONLY)  
B- 151 2 bbl (80-83, GM 2.5L)  
B- 126 Diesel (85-87, Renault 2.1L, Jeep XJ ONLY)  
C- 258 2 bbl (4.2L, 76-89)  
E- 232 1 bbl (70-79)  
F- 232 1 bbl Low Compression (71-74, Jeep ONLY)  
F- 145 Diesel (81-86, Jeep ONLY)

G- 232 2 bbl (70-74)  
G- 121 2 bbl (77-79)  
H- 290 2 bbl (68-69)  
H- 304 2 bbl (70-79)  
J- 199 1 bbl (68-69)  
L- 232 1 or 2 bbl (68-69)  
M- 304 2 bbl Low Compression (71-74, Jeep ONLY)  
MX- 242 MPI (4.0L MPFI, 86-01, Jeep ONLY)

N- 290 4 bbl (68-69)  
N- 360 2 bbl (5.9L, 70-91)  
P- 360 4 bbl (70-77)

R- 134 1 bbl (70, F-head, Jeep ONLY)  
S- 343 2 bbl (68-69)  
T- 134 1 bbl Low Compression  (70, F-head, Jeep ONLY)  
U- 150 (84-01, AMC 2.5L, Jeep & Eagle ONLY)  
W- 390 4 bbl (68-69)  
W- 173 2 bbl (84-86, GM 2.8L V6, Jeep XJ ONLY)

X- 390 (70)  
Y- 390 (70 Machine)  
Y- 318 MPI (93-96, Chrysler 5.2L, Jeep Grand Cherokee
ONLY)  
Z- 343 4 bbl (68-69)  
Z- 401 (71-77)

[rearview]

There is no X after the M and it has 6 cylinders with each hole measuring around 3.76. Pistons stamped 50 with the arrow to the front.

 

All the computer sensors are in the correct spots and the head is a 2686.

 

I'll check the block numbers when I get the 27 years of oil leakage off the block.

[HOrnbrod]

:dunno:   The head's correct. Somehow the "X" got left off the engine code. Read the block casting number when you get a chance.

[Jeep Driver]

If the x is missing, I'm wondering if the block was destined for Canada or overseas. IOWs, does the X indicate US emissions regulation compliant?

[jimoshel]

It is a pureblood renix that only saw a tow truck when I lost the clutch slave 50 miles from home. The slave was changed at 305,000 and the clutch itself was still a good clutch.

 

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Posted Today, 01:55 PM

^^  Don't know why Jim posted the above in this thread.   :hmm:

[HOrnbrod]

Ah, okay - missed that Jim. My bad.  :cheers:

[jimoshel]

Ah, okay - missed that Jim. My bad.  :cheers:

 

Hey guy. Yer GOOD.. Just NOT perfect,  IE= Human

[rearview]

 

It is a pureblood renix that only saw a tow truck when I lost the clutch slave 50 miles from home. The slave was changed at 305,000 and the clutch itself was still a good clutch.

 

 

 

Thanks for the tip. I was in the bay area where they have lots of stoplights, toll bridges and even better yet, thousands of people who do stupid things for no reason at all. I did feel bad watching her slide onto the back of the car carrier but figured it was better than bumping the fenders.

 

As to the big rigs, I have about 5 million miles under my belt and have not used the clutch other than to start and stop since I drove a M35A-1. The current generation of plastic trucks come with automatics.

 

The block is an  8933002665   

 

[HOrnbrod]

The block casting number for 1987-90 4.0 engines should be 53005535 which equates to 8933002665.
.

[rearview]

The block casting number for 1987-90 4.0 engines should be 53005535 which equates to 8933002665.

.

 

What does equate mean?

 

Are you sayingthere a math formula used to decode the 8933002665 to a 530 group?

 

Thanks

[HOrnbrod]

8933002665 is the old AMC number. Chryco changed them when they took over and dumped the 89 prefix.

 

Block Castings:

87-88 53002665 53005535 53008405 8933002665
89-90 53002665 53005535 8933002665 893300266
91-97 53008405 53010341 53020569 5302569
98-06 53010327-AB 53010328-AB 53010341 53010449 53010449-AA 53020514 53020515 53020569

[rearview]

I see thanks.

 

So now I have to find an X somewhere to go along with the M in the build date..