Mod Benefit Drawback Is it a problem? Notes
Replacement camshafts
  • Improved performance
  • Power shifted further up rev range
  • As the power band is shifted the rev limited may need to be raised to take advantage of this
  • Higher revs means better balanced engine required
  • Bigger/better valve springs will help to keep the valves under control at higher rpm - but at increased valve train wear
  • Would be advisable to go to the 205 head for shim under bucket setup or the shims may not stay put for long
  • Driveability? Do you want to make most of your power >6k rpm?


Too longer duration will need some careful setup to avoid a "lumpy" idle

An aftermarket ECU is advisable to take advantage of this setup

Popular durations are 264 and 272

Stock durations:
185 - In 236 Ex 236
205 - In 240 Ex 236

Stock lift:
165 - 7.15mm
185 - 8.2mm
205 - 8.7mm

205 cams will not fit the 165 head

205 cams will fit the 185 head

Vernier cam pulleys
  • Accurately setup camshaft timings
  • Increase power output
  • Needs a fair amount of time to set these up correctly and get the most from them


Popular choice for HKS 264 seems to be:

4 deg advance intake
8 deg retard exhaust
Forged pistons
  • Stronger
  • Lighter
  • Better heat dissipation
  • Need an engine rebuild to fit them


205 fitted with Hypereutectic pistons, a "halfway house" between cast and forged pistons
Metal head gasket
  • Will seal the chambers better
  • Able to run higher boost/cylinder pressures
  • Need to remove the head - pain
  • Needs to be sized correctly to maintain your compression ratio


Popular opinion is that the HKS gasket seals very well

TTE gasket is recommended for price/performance

Commonly available in 1.0, 1.2 and 1.4mm widths

Only fitted as standard on the 205 - 1.0mm. No other GT4 came with a MHG

Shot peened rods
  • Rods less liable to failure
  • Rebuild time...


The rods can be distorted by incorrect shot peening
Nitride crank
  • Crank less liable to failure
  • Rebuild time...


Needs to nitrided after all machining and polishing work has been completed or the "coating" will be removed

Probably not required

Knife edge crank
  • Fewer losses associated with "windage"
  • Less rotating mass
  • Machining
  • Balancing required
  • Rebuild time...


Only really talking about a few hp I think, but every little helps?
ARP fasteners
  • Stronger
  • Less prone to failure under increased loads
  • Some are lighter than stock e.g. big ends
  • Need to get at the stock bolts and remove them


ARP fasteners are available for:

Part No 203-4204


Big ends
Part No 203-6002 kit 22R

Main bearing caps