Upgrading The Engine's Top End

[ Heads | Head Gaskets | Camshafts | Cam Followers | Lash Adjusters | Springs | Valves and Seats | Guides and Seals ]

Description

This page describes the options available for upgrading the top end on 2.2L and 2.5L engines.  This includes the head, camshaft, cam followers, lash adjusters, springs, valves and seats, and guides.
 

Heads

There are two stock heads that were manufactured by Chrysler.  Both are good heads and the head that is best for you depends on what you are going to do.

There are some general improvements that can be made to both heads.  One is to use 11mm Mopar Performance head bolts (P4349736) or head studs from Forward Motion, LRE, or Mopar Performance (P4452198).  The studs do not stretch like the bolts do, and do not have to be replaced.  Another good improvement is to use a better head gasket, such as the Mopar Performance headgasket.  To allow more boost, you can install a Fel-Pro EngineSaver 0.020" head shim to reduce compression.  See the Head Gaskets section for more information.  Alternatively, you can reduce compression by using the 14cc dished pistons for the "Fast-burn" head with the "G" head.
 

The 1983 - 1985 "G" Head

Up until 1986, the stock head was a simple bath tub design (often called the "G" or "G-cast").  It flowed better than the head that followed it, and therefore it is usually the head used in performance applications.  In mid-1985, Chrysler went from 10mm headbolts to 11mm headbolts for better clamping force.

The Mopar Performance Mildly Ported 2.2L Head Assembly (P4529104) features the G head with oversized 41.6mm intake and 36.15mm exhaust valves, standard seats, springs and retainers.  There is also the Mopar Performance Big Valve Race Ported Head Assembly (P4529353) with 44mm intake and 36.8mm exhaust valves, oversized seats, and race springs and retainers.  The basic G head casting is also available from Mopar Performance (P4349065), which can then be modified to your own specifications.

Other performance heads are available from Forward Motion and LRE.  They each offer various stages of performance and many of them are better than Mopar Performance.
 

The 1986 - 1993 Fast-burn Head

In 1986, a new head was introduced called the "fast-burn", "swirl", or "782" head.  The flow characteristics of this new head increased port velocities and allowed the engine to combust the air and fuel more completely, reducing hydrocarbon emissions and slightly increasing torque.  However this head did not flow as well as the G head.  Also, porting this head will quickly disrupt the fast-burn characteristics of it.  This is why most performance heads are the G head.
 

The 1991 - 1993 Lotus 16 Valve Head

This head was introduced in 1991 and was a joint Chrysler/Lotus venture.  It featured a dual overhead cam (DOHC) 16 valve setup, which greatly improved the flow characteristics of the engine.  This is obvious from the 6500 RPM redline and that the engine put out its maximum power at 6000 RPM (8 valve heads were around 5000 RPM).  It was an intercooled setup that made the jump from the 175 HP @ 175 ft-lbs of the Turbo II to a staggering 244 HP @ 217 ft-lbs out of a stock 2.2L common block engine!  This engine was made available only to the Dodge Spirit R/T and in 1992 to the Dodge Daytona IROC R/T.

Unfortunately for Chrysler, this head had severe reliability problems, which were almost entirely associated with a porous casting and the freeze plugs that were installed in it.  They installed steel freeze plugs into an aluminum head.  The dissimilar metals have different rates of heat expansions and the resulting stresses caused the head to crack.  See Ben Therien's web page on how to deal with this problem.
 

The 1988 - 1991 Maserati 16 Valve Head

Another, little known head was a joint Chrysler/Maserati venture.  This head also featured the dual overhead cam (DOHC) 16 valve setup.  It is said to actually outflow the Lotus head and features a greatly improved exhaust manifold.  It was used in only one vehicle, the Chrysler TC, which was also a joint Chrysler/Maserati project.  This head was also used on the 2.2L common block, but featured a custom billet crankshaft, heavy duty forged rods by Casar, and custom forged pistons by Mahle.  The head is compatible with normal 2.2L internals, however, and is easier to setup than the Lotus head.

As with the Lotus head, parts are expensive.  However, unlike the Lotus head, this head does not suffer from any known reliability problems.  Special thanks must go to Rick Diogo for this information.
 

Head Gaskets

One of the biggest issues with these engines has been the head gaskets.  There have been many arguments as to which are the best.  Below is a list of all the versions that I know of.
 

The Victor-Reinz Head Gasket

This is the same gasket as the original stock Chrysler head gaskets, with all its related problems.  There is nothing wrong with the materials or construction of the gasket.  It is simply not designed properly for our engines.  Vic simply duplicated what Chrysler had done, even though it was wrong.  This gasket has a fiberous-metal construction that is fairly soft and gets over-crushed in certain areas.  This gasket can be modified so that it will function properly.  For the details about all of this, see the Replacing The Head Gasket page.
 

The Fel-Pro Head Gasket

This head gasket is a completely different design from the original Chrysler head gasket.  It features a solid-metal construction that can withstand greater pressures without being over-crushed.  It also seems to have stronger rings around the cylinders which should help support it as well.  It seems that Chrysler has finally done something about their bad head gasket design and adopted this design.  The new stock Mopar replacement gasket appears to have similar, if not the same, construction as the Fel-Pro design.  Below are the part numbers.  Items marked by (?) means that I don't know if there is a separate part number for these, or if the same part is used on both designs.

The Mopar Performance Head Gasket

This is an even tougher head gasket design than the Fel-Pro.  <details to be added soon>  It is also available in a special form to handle o-ringed heads and blocks.  Here are the part numbers:

Camshafts

There are quite a few options when it comes to camshafts.  Unfortunately, most of the aftermarket performance camshafts suffer from severe reliability problems.  One major change in the stock valve train occured in 1988 when Chrysler switched to the roller cam on all its 2.2L and 2.5L engines.  Stock camshafts were the same for Turbo I, II, and IV engines.  A mostly-complete chart of all cam specs is provided at the end of this section, which uses the reference numbers for each camshaft described below.  So far, all performance camshafts use slider cam followers because of durability problems with the roller followers.
 

1) The 1984 - 1987 Turbo Camshafts

This camshaft is the best stock camshaft available for turbocharged engines.  They use the slider cam followers.  This cam tended to have a slightly rough idle because of the longer duration and overlap.
 

2) The 1988 Turbo Camshaft

This camshaft was the first to use the roller cam followers and featured less valve duration which improved idle smoothness and emissions.  It also slightly decreased the engine's top-end performance.  This was somewhat intentional because Chrysler was trying to improve the low engine speed performance of the turbocharged engines (installing a smaller turbo, etc.).
 

3) The 1989 - 1993 Turbo Camshafts

These cams were even milder than the 1988 camshaft.  This was probably because of the 2.5L engine, who's longer stroke and displacement didn't require such long cam durations.  Chrysler was also trying to smooth these engines out at this time (balance shafts), so they may have been concerned about the idle.
 

4) The Mopar Performance "314" Camshaft

This is Mopar Performance's "Mild Competition Turbo" camshaft (P4529314).  This camshaft uses the slider cam followers and has slightly more lift and overlap than the stock 1984 - 1987 camshaft.  Unfortunately, these camshafts are prone to premature failure because of material defects that Mopar Performance intends to do nothing about.  Do not bother with this camshaft.
 

5) The Mopar Performance Super 60 Camshaft

This is the most aggressive camshaft that you can get from Mopar Performance (P5249496).  It also uses the slider cam followers and has increased lift, duration, and overlap.  This camshaft yields more midrange and top-end power.  It was designed for the Super 60 engine, which could put out over 300 hp.  It requires the use of special valve springs (P4286540) to handle the increased lift.  However, this camshaft also suffers from durability problems like the "314" camshaft.  Usually the lobes will wear off and/or the cam followers will wear out.  If you are a serious racer and don't mind replacing the camshaft and followers every season, then this is the camshaft for you.  Otherwise, avoid it.
 

6) The Forward Motion Enforcer 475 Camshaft

This is probably the most popular performance camshaft that is currently begin used.  It usually provides more mid-range power, with some improvement in the top end as well.  It uses the slider cam followers and does not have any known reliability problems, as long as the stock valve springs are used.  Hard data on this camshaft is very limited.  Although it is called the 475 camshaft, is actually has a lift of 0.460".
 
 
Cam
Valve
Intake Valve
Exhaust Valve
Valve
Installed
        
Type
Lift
Opens
Closes
Duration
Opens
Closes
Duration
Overlap
Centerline
Num.
(inches)
(BTDC)
(ABDC)
  
(BBDC)
(ATDC)
    
(intake)
1
0.430
10^
50^
240^
50^
10^
240^
20^
110^
2
0.430
8^
48^
236^
52^
0^
232^
 8^
110^
3
0.430
4^
44^
228^
44^
-4^
228^
 0^
110^
4
0.460
14^
46^
240^
50^
10^
240^
24^
106^
5
0.499
18^
62^
260^
62^
18^
260^
36^
112^
6
0.460
                

Cam Followers

There were two types of cam followers (or rocker arms) used on stock engines.  From 1983 through 1987, slider cam followers were used.  The camshaft literally slid across these followers with only a barrier of oil to protect them.  In 1988, the roller cam follower was introduced, which eliminated the friction between the camshaft and the follower.  This decreased the parasitic drag of the camshaft and also decreased valve train noise and camshaft wear during startup.  The roller camshaft had to be specially case-hardened because of the small amount of contact area between the cam and the roller.

There are no performance camshafts available for the roller cam followers because the stock followers are not strong enough for heavy duty valve springs and they cannot lift the valve more than 0.460".  However, there are two performance slider cam followers available from Mopar Performance.  One is the 2.2L Sintered Iron Rocker Arm Set (P4349147), which features a special hardened sintered iron insert for the cam sliding surface.  This increases the life and strength of the cam follower.  Also available is the 2.2L High Performance Race Rocker Arm (P4452064), which has extra length that is designed especially for high lift camshafts (such as the Super 60 Camshaft).
 

Lash Adjusters

The lash adjusters used on all turbocharged engines are hydraulic and therefore need no adjustments.  They are the same for all years of 8 valve heads.  Mopar Performance offers a High RPM Hydraulic Lash Adjuster (P4529894) that isn't supposed to collapse at high RPMs or when using race valve springs.
 

Valve Springs

There are a couple of  types of springs available.  The stock springs are sufficient for most applications where stock valves and a maximum of about 0.460" of valve lift are used.  Larger valves or more lift may result in valve float.  Mopar Performance offers a few different performance valve springs.  The first is the General Purpose Performance Valve Spring (P4286813), which has an installed height of 1.654" to 1.70" and is good for a cam lift range of 0.430" to 0.460".  The Race Valve Spring (P4286540) is a single damped spring that has an installed height of 1.68" and a cam lift range of 0.490" to 0.550".  You must use these springs if you are going to use the Super 60 camshaft.  There is also the Race Dual Valve Spring (P3412068) that is a dual damped design with an installed height of 1.685" to 1.700" and has a cam lift range of 0.525" to 0.600"
 

Valves and Valve Seats

As far as valves are concerned, the sky is the limit.  Oversized valves and seats are available through Forward Motion, LRE, and Mopar Performance.  Avoid "siamese" valve seats, where the intake and exhaust seats are touching.  This design does not allow for proper heat expansion and the exhaust seat will transfer heat to the softer intake seat, and the shape of the seat can become distorted.  The valve will not sit properly and low compression and severe valve wear can result.  The stock valves are generally large enough with a properly ported head and good camshaft.  A good porting job with stock-sized, backcut valves can actually out-flow a big valve race head when done properly.  A multi-angle valve job will also increase flow through the valves.

"G" Heads use 112.2mm valve stems, while the Swirl head uses 114.3mm valve stems.  Mopar Performance also sells stronger valve stem locks for intake (P4452031) and exhaust (P4452030) valves.
 

Valve Guides and Seals

In general, the stock valve guides are more than sufficient.  Bronze guides are available through Forward Motion.  Viton Valve Seals are available through Mopar Performance (P4349121), which can withstand higher temperatures than stock seals.  This doesn't make sense to me, since the stock seals should be Viton anyway.
 
 
 
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This page is maintained by Russell W. Knize and was last updated 02/10/99. Comments? Questions? Email minimopar@myrealbox.com.

Copyright © 1996-2003 Russ W. Knize