14 August, 2007
need to carry out this conversion - special inlet manifold, inlet manifold
gasket, 2x rocker cover gaskets, 3x Weber 40DCNF carb's, linkage kit, fuel
connector pipe, main jets/emulsion tubes/air correction jets/34mm venturi's
for carbs, vacuum pipe fitting for servo take-off, water pipe fitting for
heater take-off, M8 threaded rod for studs (this was the thread used in
this particular manifold by the manufacturer, taps for 1/4" NPTF thread
to allow fitment of air/water fittings, 3x high performance air filters.
is a set of 3 gasket/repair kits for carbs - a must to save time later (carb's & carb parts are difficult to obtain & can take months to arrive).
to follow before assembling parts on car
As I have just
carried out this conversion, I hope this article will help anyone who decides
to do it - saving them the trouble of sourcing the right parts from various
What you need
to do is make sure the inlet manifold is free from casting flaws, and check
that all the inlet ports are smooth from carb base through to head face. Once
this has been checked, before getting the drill & grinding stones out,
make the studs for the 3 carb bases. Each one needed to be 38mm in total length
on the manifold I bought - although this may vary from item to item. You could
have the studs longer on 3 of them, but the acceleration pump housing above
one stud means this was the maximum height possible - allowing the fixing
nut to be fully threaded once tightened. See pictures on the right for example.
Once you have
4 studs in a carb mount, place a gasket over these to check both ports on
the manifold are no smaller than the gasket. Ideally the ports should be flush
with the gasket, but it's not really a problem if they are slightly wider.
The reason for this is to make best use of the inlet ports - smaller openings
mean less air/fuel mixture will enter the engine, and a "step" in
the flow of air caused by a smaller bore in the manifold will upset the airflow.
Try to get each port identical to allow for the best possible match of airflow
for each cylinder. Going back to the procedure, mark with a scribe or pencil
the amount to be removed, then take off the gasket, unscrew the studs, and
grind out exactly to you markings using a grinding attachment on a drill.
The best type of drill to use for this type of work is an air drill (capable
of very high rpm), with a carbide burr attachment (very hard material which
will make light work of this job - especially as it's aluminium). An electric
drill with a stone attachment will suffice if you have no access to the above,
although running at a slower speed will take longer, and the stone attachments
tend to clog up if you press too hard. As always, please ensure you wear good
face & eye protection.
happy with the ports on the carb side, repeat the process on the underside after
marking out the inlet manifold gasket in the same way. Only do this if you are
sure the inlet gasket lines up correctly on the cylinder head though - as again,
any smaller opening as air/fuel flows into engine will cause flow disruption.
If you have already removed the old inlet manifold, you can test fit the manifold
on the heads, and using a piece of metal coat hanger wire with a 180º tight
bed at one end, sharpened to a point, insert through the carb opening and scribe
a line on the inlet manifold face where it joins to the cylinder head. This
method will allow a better port match hence improving the airflow. Repeat this
process using an unbent coat hanger "scribe", to check cylinder head
face has no "protrusions". If this occurs, you will need to remove
the head or heads to match the inlet ports with the manifold (not likely, but
is possible). The gasket should really fit on the heads without much of a problem.
Next on the preparation
is the air take-off for the brake servo, and the water take-off for the heater
matrix. The manifold I used had a 1/8" NPTF threaded hole in no. 3 inlet
port (for the servo fitting), an identical threaded hole at the back and front
of the thermostat housing end of the manifold. One for the temperature sender
(nearest no. 4 cylinder under the thermostat), and one for the heater pipe
(near the distributor - also under the thermostat). I decided that the servo
& heater pipe holes were too small because:
available for 1/8" NPTF allow a maximum internal diameter of 6mm for
the pipe to attach to. The standard internal pipe bore for the servo is 3/8",
and the heater pipe is 1/2" or 5/8". This internal pipe diameter
of 6mm was around 4mm - probably OK for the servo, but was way too small to
allow a generous flow of water to pass to the heater matrix - winter driving
would have suffered (for those of you who drive your TVR in the winter....!)
BSP fittings are similar to NPTF with the exception of the thread being slightly
different. Don't let anyone tell you they are interchangeable because you
don't want a leaking water or servo pipe, and once the thread is damaged you
will be forced to go up to the next size fitting. NPTF thread is slightly
deeper, and I suspect this is used for alloy parts as it ensures less chance
of thread damage. BSP thread is more likely to strip if overtightened in such
a soft metal. Lastly, the fittings are available in brass, mild steel, and
stainless steel. I would opt to fit the brass or stainless items - but brass
is safest if you want to protect the alloy thread.
What I decided
to do was fit a 1/4" NPTF thread fitting for the servo take-off, with
a pipe "tail" of 10mm diameter. This matched almost exactly the
original Ford manifold's take-off - meaning the original pipe could be swapped
over. The existing hole was drilled out & tapped with a 2nd stage tap
(this allows a nice tight fit & longevity of thread if removal of fitting
is to be done occasionally). See pictures on right for procedure.
I carried out
the same operation for the heater hose take-off, but this time I was limited
to the same maximum internal pipe diameter of the above servo pipe using the
¼" NPTF fittings. The problem was that the heater pipe has a 1/2"
to 5/8" int. dia. pipe, so this fitting would be too small. NPTF fittings
are limited, but BSP thread fittings are much more suitable, so to overcome
this I purchased a male to male ¼" NPTF to ¼" BSPT
fitting, a ¼" BSPP female to ¼" BSPP female fitting,
then finally a ¼" BSPT male to ½" pipe tail fitting.
Internal bore was ideal for the heater now - impossible using the fitting
as per servo take-off which would screw directly into this hole. Although
a long length of brass fittings compared to original, this was my only choice
unless I went up to 3/8" NPTF fittings. This would be possible, but the
inlet manifold would start to become thin around the hole & could possible
crack if fitting too tight. I am still hunting for a ¼" NPTF male
to ½" hose tail fitting - this would much improve the appearance
of this area, and would be less likely to damage manifold if someone/something
were to lean on the pipe! See picture further down for appearance of the final
third hole above No.4 cylinder was already a suitable thread size to accept
the standard Ford temperature sender unit - it simply screws in. A plan for
the future is to fit a capillary water gauge as I feel they are more accurate
- so for this I will fit an in-line adaptor tube which has a take-off for
such a fitting. This will mean plugging the electric sender's hole - again
with a 1/8" NPTF fitting. Just one point to note is that the temperature
sender was originally located on the top of the manifold - not possible now
due to front carburettor platform!
Final note on
threads - BSPP means parallel thread, BSPT means tapered. Obviously a male
tapered fitting goes into a female parallel fitting & vice versa.
servo take-off by drilling hole
new 1/4" NPT thread
basics - but there are some extra parts you'll need! All above is available
from Ric Wood (see links)
stud thread clearance
studs & gasket
new 1/4" NPT thread pipe fitting (with 10mm int. dia. pipe tail)
Do the same for
the heater pipe take-off... Picture of this fitting later in section
the temperature sender hole at 1/8" NPTF - this is the original size thread
- although in a different position to before
report - visit to Ric Wood on 1st October 2002
works & the engine runs, the only way to tune the engine for maximum efficiency
& performance is to take it to a specialist with a rolling road. This
is basically a set of rollers which allow the car to be "driven"
while stationary, with the wheels allowed to spin as if on the road. This
is important as the engine is under the correct loadings - simply revving
the engine in neutral will not show up any fuel or ignition errors - they
will only become apparent when driving. Also, there may be an unnoticeable
error or poor setting which could cause engine damage - this will only show
up on the rolling road.
Now, I tuned
the engine to the best of my ability, but was still not happy with the performance,
considering approx. 220bhp should be available now, compared with a standard
V6 Essex producing 138bhp.
The car was booked
in, and driven to Ric Wood's in Davenport (near Manchester) for early morning.
After removing the bonnet to aid cooling (it has a quick release mechanism
& wiring connector), Ric put the car on the rollers and placed a large
fan against the radiator (as there is no airflow when stationary this powerful
fan keeps the engine temperature down). The car was warmed up & driven
through the gears, with various checks being made. Ric's expertise is second
to none with these engines, and he immediately noticed a large reduction of
power which he said was due to the cam timing being incorrect! Now, I spent
a great deal of time when building this engine, but was not aware that the
steel timing gears can have a manufacturing defect where the timing mark "dot"
is one tooth out! It appeared that the engine was struggling to breathe correctly,
and also explained the phenomenal fuel consumption on the journey up to Manchester
(nearly 2 full tanks of fuel in 140 miles!). Due to this, and a faulty gauge,
the car ran out of fuel on the rolling road, much to my embarrassment, so
please make sure the tank is full when you go to a rolling road.
Ric said the
first thing to do was to remove the front cover & re-set the cam timing.
Luckily he was able to do this the same day, so I took a train to Manchester
for the rest of the day - the station is literally at the end of the street
so very convenient.
Upon my return,
the cam timing had been done, and Ric now said that the performance had improved,
but the exhaust & carbs needed further work to increase further. Basically,
a standard TVR exhaust is fitted, and the two rear resonators are possible
the cause of a large loss in power - due to not being straight through design.
This is my first task as the power at the wheels is down approx. 30bhp from
what it should be giving. Also, the carbs have 30mm inlet "ducts"
built into them as can be seen on the photos, but these seriously affect the
intake flow with my bespoke air filter - so they need to be cut down to flush
with the air filter baseplate - allowing some special stub stacks to be fitted
(Ric does cast alloy ones in two height sizes - essential to allow smooth
airflow into carbs. Fuel jets & chokes were all recommended by Ric, so
well in fact that no fuel adjustments had to be made except for at idle. He
also set the standard distributor (now with no vacuum advance) to its optimal
setting for maximum advance.
So, that's the
story so far. The bhp is approx 120+ at the rear wheels, although full revs
were not reached as the further work needs doing before a final power run.
Ric reckoned it should be around 170, so the exhaust needs urgent attention.
You may ask where the 220bhp comes from - well that's at the engine - you
need to take off a some hp for gearbox & diff friction.
was amazing - the first time I've felt at ease driving the car. Power was
awesome compared to the trip up, so make sure you set up the cam timing correctly.
The engine sounds really good and just keeps pulling - the car now needs those
uprated front brakes! Certainly it is a worthwhile mod. as the car is transformed
into a real animal. Part throttle & deceleration now create a pop or six,
which is something that will take some getting used to, but adds to the fun
of driving. Needless to say this car won't be fitted with a stereo.....
For further updates, please see members section - as the mod's have continued since this artcle was published. To become a member, please see navigation bar at top of page. If you see no navigation bar, please click on the icon
- removal of existing inlet manifold & carburettor
Removal of the
existing inlet manifold can be done with ease, once rocker covers have been
removed (see roller rocker section for instructions). Then, follow the steps
ports to match gasket (only mark out with gasket and studs fitted).
throttle cable clip, then cable...
leads & distributor cap.....
covers, then inlet manifold complete (8 bolts)
temp sender wire....
studs to inlet manifold using 2 nuts interlocked
ready to fit
cleaning up the head & block surfaces, place a new gasket into position
- making sure it's the right way round. The curved cork insert is at the distributor
trial fit of the triple carb inlet manifold, not as straightforward as it appears
here - see next photo for problem...
inlet manifold casting has larger than standard protrusions which foul the pushrod
guides..... the manifold was planned to be CNC machined in the future so would
not require any filing.
to be filed down to allow correct position! This manifold is drilled &
tapped for carbs/thermostat housing and main mounting studs, but you will
need to check everything fits methodically as it is not a mass production
the manifold fits, you will need to source some 5/16" threaded allen head
bolts to replace the standard ones - this manifold has fitting holes very close
to carb bases (too close for a standard bolt). Also, the bolts are a different
length - requiring cutting to size. I bought 4x 2¼ and 4x 2½ bolts
which needed trimming but were the closest I could get. More problems were the
distributor - it just fitted down into its hole but scraped on the end
of the manifold. It also fouled in the area of the No.1 cylinder inlet manifold
bolt when twisting for timing adjustments - the manifold required filing down
the here. Lastly, the worst problem was the mis-alignment of the rocker cover
holes already drilled & tapped when bought. This was a nightmare - the only
sensible way to fix was to put a needle file in a drill and ream out the rocker
covers to allow bolts which fouled (two per cover) to line up! E-mail me for
detailed info. on this if you're still willing to do this mod!
final test was to try the carbs, and see which way round was best for the engine.
This is the way to do it - other way round means distributor cap fouls carb
body, and throttle cable routing would be much harder - distributor is in way
and cable would have to pull from front of engine!
view from the other side - the choke cable will have to pull from the front,
but easier to do than the throttle - and I had a cunning plan to do this!
choke bracket fixes to a single stud - the middle carb's offside front stud.
A tang on the bracket stops it moving towards & snagging the throttle pump
cam. This will be removed as the choke is not required with these carbs!
much thought I fabricated the throttle bracket (right), and one for the choke.
throttle bracket fixes under the rear nearside inlet manifold bolt, and also
the nearside rear carb stud. I will fit a stud in the inlet manifold here so
bracket & carb can be removed without disturbing manifold - undoing this
with a hot engine could cause a warped manifold, and/or an internal coolant
front of the installed manifold showing the water take-off for the heater using
adaptor pieces, and the standard electric coolant temp. sensor. The distributor
although fitted here was taken off and swapped with a non-vacuum type Aldon
performance type unit. You can retain the original distributor by fitting a
"T" piece to the servo take-off for an extra vacuum hose (or by drilling/tapping
take-off problem solved! (See text)
used a K&N filter element (E-9030 for a standard replacement for early Honda
Accord), along with hand made aluminium base & temporary top plates. The
filter is just right to allow clearance at rear of engine where Turbo bonnet
vent is. The ideas is to get another K&N element which can be fitted to
the top of the above element - allowing airflow from all sides. Template made
of paper was done using AutoCad with my measurements - then printed out onto
paper. This saved a lot of filing and time.
fit of baseplate demonstrated here
idea of air filter layout