Blocks FAQ

[John]

4.0 Blocks

The Jeep 4.0 I6 blocks for our stroker.
Year Casting No
1987-90 53005535
1991-95 53008405
1996-98 53020569
1997-?? 53010341
1999-04 53010449

Starting in 1996 and continuing until the end of their production, main webs of blocks were cast with extra ribbing and given a main bearing girdle to stiffen the motor.
More to come
John

[1bolt]

John add

53010328 (2000+ wrangler/XJ)
53020569 (2000+ Grand Cherokee, some bolt boss and MM differences)

I just finished telling someone that all the 4.0 blocks will work in all similar year Jeeps, and I got schooled. Appearently this is not true, just how easy or hard it would be to make a 2000 ZJ block fit a 2000 TJ is another matter... I suspect trivial. none the less

[Flash]

John, this is good info and i felt it belonged here as well
----------------------------------------------------------------------

Here is some info on further dating blocks.
This code is on the block below the spark plug holes.
401MX12

* 4 = Year (1994)
* 01 = Month (January)
* MX = Engine Type/Fuel System/Compression Ratio (MX is a 243 CID, multi-port fuel injection system with 8.8:1 ratio
* 12 = Day of month of engine build

Other code considerations are oversize or undersized components. This information is stamped on the boss between the ignition coil and the distributor.

Undersized

* P = One or more connecting rods bearing journals
* M = All crankshaft main bearing journals
* PM = All crankshaft main bearing journals and one or more connecting rod journal

Oversize

* B = All cylinder bores
* C = all camshaft bearing bores

Source is Jeep Engines, Speed Secrets & Racing Modifications For Jeep-Built 4,6, & V-8 Engines.
John

[Flash]

Courtesy of John post,
I felt it belong here.
Edited 6/09/08 to include early 4.0 data

Deck height is 9.450 to 9.456 inch or for those metric inclined 240.03 to 240.18 mm. Data source Mopar Jeep Engines book 3rd. Edition & 1999 Cherokee service manual, HO engines.

But if we go back to the early 4.0 engines, From Mopar Jeep Engines 3rd Edition & the 1989 Cherokee Factory Service Manual.
Deck height 9.429 to 9.435 inch or 239.49 to 239.64mm.

[Flash]

Originally posted by John in this post:

viewtopic.php?p=2804#p2804

For illustration.

For illustration.
Deck height is the distance between the crankshaft centerline and the deck surface of the block.

1981 4.2 engine
Deck height = 9.487 - 9.493 inch or 240.97 - 241.12 mm
.0149 inch or .376 mm below deck
CR 8.0:1
Pin bore CL to top of piston 1.651 - 1.655 in or41.74 - 42.04 MM

1989 4.0 Engine
Deck height = 9.429 - 9.435 inch or 239.49 - 239.64 mm
.0215 inch or .546 mm below deck
CR ? Different normally reliable source 9.45:1
Pin bore CL to top of piston 1.651 - 1.655 inch or 41.94 - 42.04 MM

1999 4.0 engine
Deck height = 9.450 - 9.456 inch or 240.03 - 240.18 mm
.0215 inch or .546 mm below deck
8.8:1 CR
Pin bore CL to top of piston 1.599 - 1.603 inch or 40.61 - 40.72 MM

All above data from Mopar Jeep engines 3rd. Edition

Then I go to the 1988 FSM and find for both the 4.2 and 4.0 CR listed as 9.2:1

Anyone else find this interesting.
John

[milner]

Original info. can be found here:

http://www.offroaders.com/tech/jeep/eng ... c258i6.htm

The 258 can be identified by the 4th character of the engine build date code ("A", "B", "C" or "M"), stamped into the engine block below and between the number 2 and 3 spark plugs. An engine stamped with "B" is an early 258 with a 7.6:1 compression ratio. "A" and "B" are engines with 1-barrel carburetors, while "C" and "M" are 2-barrel. "M" originated in Mexico. Other codes ("E", "F", "K" and "L") are 232 engines.

[Plechtan]

Maybe this should be move to FAQ section

Cylinder spacing on a 4.0 Block is 4.380" center to center. Lifter bore spacing is 2.02 center to center .903 lifter, Center pushrod, oil through pushrod.

The Valve spacing is 1.940 on a stock jeep head. Many people move the intake closer to the exhaust and change the spacing to 1.900

[SilverXJ]

Two very good article on some block differences:
http://www.pera.org/articles/eb40319.htm

http://www.enginebuildermag.com/2006/05 ... ld-friend/

I also wanted to put this here since it shows some differences between TJ/WJ and XJ blocks: http://www.jeepstrokers.com/forum/viewt ... =15&t=1047

[SilverXJ]

A good thread on some reasons why you don't want to put a 1999-2004 WJ or 2000-2005 TJ block into an XJ or vice-versa. http://www.naxja.org/forum/showthread.php?t=1015349

[SilverXJ]

Just to summarize and correct:

8933002665, 53005535: 1987-1990 Renix blocks

53008405: 1991-1995 YJ, XJ, ZJ

3010341, 53010449, 53020569: 1996-1998 TJ, XJ, ZJ (except 1998 ZJ)

53020514, 53020515: 1998 ZJ

53010449AA : 1999-2001 XJ, 1999 TJ

53010327AB, 53010328AB: 1999-2004 WJ & 2000-2006 TJ