Identifying a Logic Module

Ever wondered what those three digit numbers hand written on the logic module for 1984-1987 made Chrysler vehicles?  They actually are the last three digits of the part number of the logic module itself.

From 2012-2013 Mopar Reman Catalog

 

 

More than likely, writing the number on the circuit board itself prevented confusion when the board were inserted into the case at the factory.

Head Gasket Guide

There are two basic head gaskets used in the 2.2/2.5L SOHC family of vehicles.  Illustrated below is the non cross drilled style of head gasket, Mopar part number 5281064.  This is the same style as the former Mopar Performance P4452005 head gasket.  This gasket has open steam ports but closed cross drilled ports.  After a short hiatus, these gaskets are now in stock at dealers under part number 5281064AB for $50.20.

Non cross drilled style

The other style head gasket is the cross drilled style, Mopar part number 5281065.  This is the same style as the Mopar Performance P4452006 head gasket.  Unlike the stock gasket, the Mopar Performance part features double cross drilled ports.  Notice in the below illustration how there is only one set of cross drilled holes (highlighted green) between the cylinders.  The Mopar Performance gasket will have another set of matching holes towards the front of the block.  No production vehicles came equipped with double cross drilled blocks.  This style gasket blocks off the steam ports to force coolant through the cross drilled ports to increase head gasket life by lowering head gasket temperature between the cylinder bores.  This gasket should not be used with a non cross drilled block because of potential cooling issues.  The Mopar Performance P4452006 head gasket has been superseded to part number P4452006AB.  It lists for $92.85.

Cross drilled style

The last style of gasket worth mentioning is offered in the aftermarket.  It features open steam ports and double cross drilled ports.  When used in a cross drilled block, instead of most of the coolant flowing  through the warmer cross drilled ports, they are divided among both the steam ports and cross drilled ports.  This may cause higher head gasket temperatures in a cross drilled block.

Aftermarket style

Below is a list of head gasket part numbers for each year and engine combo.  Part numbers highlighted in blue have been superseded to part number 5281064, non cross drilled style.  Part numbers highlighted in red have been superseded to part number 5281065, cross drilled style.

SOHC--Head Gasket Part Numbers
	2.2	2.2 T1	2.2 T2	2.5	2.5 T
1985	4105468
1986	4387319	4387319		4387319
1987	4387319	4448301	4387837	4387319
1988	4448301	4448736	4448302	4448301
1989	4448301		4448302	4448301	4448302
1990	4448301		4448302	4448301	4448302
1991	5281064			5281064	5281065
1992	5281064			5281064	5281065
1993	5281064			5281064	5281065
1994	5281065			5281065
1995				5281065

Of interesting note is the application of the non cross drilled head gasket throughout the 1990s.  Many online sources indicate cross drilled naturally aspirated blocks existed as early as 1990.  The factory parts manual disagree, showing non cross drilled head gaskets were still in use as of the 1993 model year.  The factory service manual of the same model year contradicts this by omitting the illustration of the non cross drilled gasket, showing only the cross drilled gasket was available.

This contradicts the popular notion that "late 1990-1995" naturally aspirated blocks were cross drilled.

It seems 1993 may have been the cross over year for naturally aspirated blocks.

Additionally, the factory parts manual lists the wrong application of the cross drilled head gasket in 1987.  The above chart has been corrected to show that 1987 "EDR" code engines use head gasket part number 4387837.

Opinions / Observations

The following is a collection of opinions and observations on what is preferred in a head gasket.

Conjoined Fire Rings

Non conjoined fire ring

Conjoined fire ring

Many prefer conjoined fire rings over non conjoined fire rings.

Cross Drilled or Non Cross Drilled

Dave Zelkowski, a former Chrysler Engineer involved in the development of the 1980s Turbo Dodges, states "The purpose of cross drilling is to reduce the temperature of the head gasket between the cylinder bores."   Based on comparing the two styles of factory gaskets, it seems that the non cross drilled style head gasket allows coolant to pass through the steam ports while the cross drilled style head gasket blocks those steam ports to force coolant to pass through the cross drilled ports. 

In the aftermarket, one common feature is for the head gasket to have both cross drilled ports and steam ports open.  This gasket is acceptable for use in both cross drilled and non cross drilled blocks.  In cross drilled blocks, however, any cooling advantages that the factory intended are lost.  This may lead to the unexpected failure of such a gasket in a cross drilled application.

Mixing and Matching

If you have a vehicle that uses different heads or blocks than factory, use the below guide as a suggestion as to what gasket style is preferred.

Head	Block	Suggested Head Gasket
Cross drilled	Cross drilled	P4452006
Cross drilled	Non cross drilled	5281064AB
Non cross drilled	Cross drilled	5281064AB
Non cross drilled	Non cross drilled	5281064AB
Unknown	Unknown	Aftermarket

Special Notes

This guide is only a guide.  It is based on the factory service manual, factory parts manual, and limited firsthand experience.  It excludes many of the special head/block combinations found on Shelby L body vehicles.  Those vehicles got some crazy weird combos that sometimes required head gaskets not mentioned above.  It also excludes much information about double cross drilled applications found in limited production / prototype vehicles.

Advance Turbo Dodge Quiz

1. What is pictured above?
Keyless Entry Module
MODULE, Keyless Entry Receiver
Security Alarm
MODULE, Security Alarm

2. What type engine is pictured above?
TI Engine
TII Engine
TIII Engine
TIV Engine
3. What is the factory color for the valve cover of a 1991 TI engine?
Black
Silver
Grey
White
4. What is the size of the oil restrictor located in the block?
0.090"
0.125"
Either 0.090 or 0.125, depending on model year
There is no oil restrictor located in the block.

5. What is wrong in the above factory illustration?
It is missing a set of cross drilled holes.
It is missing a set of steam holes.
It is missing a hole for a head bolt.
This is not a gasket for the 2.2 / 2.5 engines.

6. The above symbol is most associated with with what company?
Valeo
Bosch
Mopar
Marchal
7. Some vehicles have a P.A.R harness on the vacuum line to the wastegate. What does PAR stand for?
Positive Actuation Restriction
Purely Asymetrical Resistor
Positive Actuation Restrictor
Point of Actual Restriction
8. The 1987 Shelby CSX featured struts by what company?
Monroe
Mopar
Koni
Carrera

9. Of the above pictured wheels, which one is made of plastic?
7402
7404
7407
7408

10. Of the above pictured vehicles, which one has the correct factory engine?
Left
Right
Both
Neither
Score =
Correct answers: