[E-Type] XJ6 Injection Head or STD Head Modded ,Cams and more?

Hi listers,
Just reading through the list thought some of you might be intereste in
Someone said,
Is there any advantage/disadvantage to the fuel injection head? I’ve
heard conflicting stories.

The advantage is they are plentiful.
The disadvantage is they are nearly always corroded.

The larger inlet valve gives no benefit to a standard or even midly modded
The port shape does,it’s better around the Inlet valve guide to valve seat.
You will not feel any difference in performance.
The HP gained is all up high and it’s about 4 HP.
An earlier Ser1 or 2 XJ6 Head fitted to a series 3 XJ6 with fuel injection
is actually
more responsive in the lower Rev Range and pulls better, I tow with our
Series 3 XJ6
and fitted an earlier head to get better torque.
The greater Velocity with the Smaller Inlet Valve gives better HP,that’s why
I never use the larger
Inlet Valves in Moderately Hotted Twin Cam Engines.

If you take the inlet and Exhaust Valve throats out to max and do a Tri
angle Valve seat it will make more Hp
then the larger 17/8" Inlet especially on the 3.8.
On the 4.2 unless you are going to Rev it High and must use mild cams, you
will get only a slight HP
increase which is not measurable on the road.

The best and easiest thing to do is cut the valve throats out to Inlet,
1.550" Exhaust 1.450" the Head will flow more and make more power then a
ser3 XJ6 Fuel Injection Head,still have greater velocity.
Unless you want to spend Megga Bucks on Upgrading the E-Type Head,Move the
Inlet Valve, Move the Inlet Port,fill in the Exhaust Port, make it Oval or
Round, Round holes flow more,use Real Big Valves and Big Tough Cams With 302
Advertised Duration stick with the standard Valve sizes.
To make 400HP the Inlet Port has to be moved and enlarged through the Water
Jacket and Welded up,or a new port turned up from Alloy and pressed in and
Fettled but not Polished, polishing does not help flow it allows raw fuel to
go through and out the exhaust,the Rough Surface Port Breaks up the Raw
When the head is finished it must be put into a Tank of Loctite and the
Loctite is drawn through by Vacuum.

For serious modifiers, the Triple Su 2" are too big, they never open right
up because the Jag head will not flow enough,Better to use 13/4" Su’s,taper
bored from 17/8" to the Butterfly, some other mods are also required
but not much,they will give far better response and the Twin Cam will make
upto 370Hp with them,if you want more you have to rev it to 7500 RPM and use
the 2" Su’s,modded for more response.
Either set up has always given me more HP and torque then 45mm Webers on a
Warnerford Manifold
if you make another better designed manifold the Hp improves but the Su’s
still give more.
If you go to 48mm they make as good power as the Su’s but do not perform as
well down low and mid range as the same engine on Su’s,Webers sound fast
Atleast twenty Hp can be found in a modded 3.8 E-Type Manifold it works
better then a 4.2 Manifold.
With either manifold they heat the incoming charge too much,blank the water
passages off and screw the big Hex plugs out of the Head Valley near the
Spark Plugs and take the Collant away from there.
The cooler incoming charge and modded 3.8 Inlet manifold gives about twenty
That is on a Cammed Engine with about 274 Duration @ .050 Lift.
cams, any smaller don’t really make much power.
The “D” Type Grind with 3/8" Lift forget it it’s a Toy better to use
standard ser 3 XJ6 and move them and advance up overall by 6 Deg get some
torque to pull the overgeared 3.07-1 Diff that some people want to use.
A tip the best street cams and club racers are a Profile put out for a VW
PASSAT about .415 Lift 32 62 62 32 timing you will have to degree them in.
Dont say that’s similar toa D type they are nothing like a D Type these work
better and have completely different opening and closing Rate.
.050 Lift is the standard for checking valve timing, no clearance,avertised
timing is the one used so you do not really know what it is.
Terry Handley
Bathurst Australia

At 12:25 pm 1/13/99 +1100, Handley wrote:

better to use
standard ser 3 XJ6 and move them and advance up overall by 6 Deg get some
torque to pull the overgeared 3.07-1 Diff that some people want to use.


I am interested in the effects of advancing the standard cams. Does this
(on its own) give a better torque/power compromise (for street use)?

In particular, I am wondering what valve timing would be best for the
engine I am installing in my e-type.

The engine is essentially a standard 11.5:1CR HE engine. It will have
programmable ignition, but initially will use a standard 1988 euro spec
injection ECU (custom engine management later). Likewise, it will
initially have standard injection inlet manifolds, but I may get some high
torque manifolds from Bill White when I fit the engine management system.

The car is purely a street driver, with (relative) fuel economy being an
issue for my wife.

I have read a couple of books which suggest that 3 - 6 degrees cam advance
will improve torque and economy at the expense of the top end power curve,
but have not found anyone who has tried it on a V12.


Mike Morrin
1973 V12 2+2