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Ford 4.0 vs 4.1 I6 Engines |
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Head
- 4L has larger ports in the head standard and repond better to turboing if used totally unmodified
- 4L has larger inlet and exhaust valves standard, 4.1L has room for
bigger valve but this get expensive doing new valve seats etc
- 4L will flow around 430 hp, the 4.1L around 410hp when ported to the max virging on hitting wter jackets, with big valves etc.
- 4L has a bigger chamber so you only need 11CC dish to get 8.5:1 compression where the 4.1L needs the 27.9cc dish piston
- 4L valves are more canted so they need valve reliefs cut into the
pistons, 4.1L engines have plenty of piston to valve clearance
Inlet manifold
- 4L have better inlet manifold design. Either EB-ED style or EF-AU multi path manifolds are better than the XF banana manifold.
- Turbo fords either 4L or 4.1L really responds to custom short runner manifolds with big plenums
- XF right through to AU engines use a similar size throttle body
Block
- 4L has slightly stiffer block but the 4.1L block is proven to handle 900 hp so doesn’t matter unless you want 900+ hp.
- 4L has the start motor on the passenger side which allows more room
on driver side for exhaust. Free flowing exhaust is critical on a turbo
engine so this is quite a big advantage. You can however fit a 4" dump
out of a 4.1L engine in a Cortina so again this is something you can
work around. Again 4L might be advantage if you need a 5" dump (1000hp
region)
- 4L block has a BW40 bellhousing pattern so a $400 adapter and
different flex plate and converter is needed if you want to run a C4.
4.1L came standard with C4 in XD falcon towing packs.
Crank
- 94DA 4L has the fully counterweighted crank although this can be grafted into an 86DA crossflow block anyway
Conrods
- 4L and 4.1L have essentially the same conrods although 4.1L are
imperial bolts so ARP bolts from 289 windsor fit easily. ARP now do rod
bolts for the 4L but they are harder to get
- No one makes off the shelf aftermarket conrods for either engine. The
aftermarket, Atomic, PAR or Spool conrods for BA engines can be used
with custom pistons in either engine.
Pistons
- 4.1L happily take the 27.9cc dished ACL duralite which esily get you
8 - 8.5 compression you need. 4L has a bigger chamber so the 11cc dish
ACL race series piston gives about the same result.
- No one makes off the shelf forged pistons for either 4L or 4.1L
engines, 4L is a bit harder to get custom for as the valve reliefs
complicate it slightly.
Fuel System
- No differences here stock fuel pumps, injectors and regulators are
not much use for a turbo engine regardless of what engine they were on.
- The fuel rail used on both engine is pretty good and with minor mods can support 1000hp fairly easily.
Cam and Valvetrain
- A stock 4L cam is around 114 lobe centres standard so works quite
well on a mild turbo engine. When you want to go chasing 500+ rwhp the
4.1L has a lot more cam profiles available right up to full roller cam
setups with very aggressive lift rates. The 4.1L valve train is
identical to the 351 cleveland and roller lifters from a 460 big block
ford engine can be fitted in the lifter bores. The 4L is limited to
about 230 degree duration @ 0.050" lift on a 114 lobe centre cam which
is good for around 550 rwhp engine combination.
- Both 4L and 4.1L have pretty poor valve springs that should be
ditched. 4.1L engine have readily available double valve springs and
retainers available fairly cheaply, I am pretty sure 4L are easy enough
to get good springs for also.
- 4L have roller rockers standard which are good for reasonable sized
cams. If you get to the stage the 4L is breaking rockers then there is
no billet items available. 4.1L use Cleveland rocker gear and Yella
Terra roller rockers are readily available but these are around $400 -
$800 a set depending on what type you get.
- 4.1L have a pretty ordinary timing chain standard but a rollmaster
double row chain is only about $90 which allows the cam to be dialled
in with the multi keyways etc. 4L have a double row chain standard but
being OHC the chain is a lot longer and has the hydraulic tensioner.
The 4L chains have been known to break on cars racing the Saloon car
series. There is no stronger chain available for them. Cam adjustment
can be done buy using a vernier cam wheel on the cam sprocket. This is
convenient as it can be adjusted by only removing tappet cover.
- Both engine use the same oil pump. 4.1L drive off the cam, 4L have a
dummy shaft in the front section of the block where the cam used to be
just there to drive the dizzy and oil pump.
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