Fitting Triple Weber 40DCNF carburettors to the Ford V6 Essex                        

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Page last updated 14 August, 2007

Parts you 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.

Also shown 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).

Procedure 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 suppliers.



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.

Once 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:

The fittings 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....!)

Now, 1/4" 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 assembly.

Finally, the 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.


Enlarge servo take-off by drilling hole
Tap new 1/4" NPT thread
Kit basics - but there are some extra parts you'll need! All above is available from Ric Wood (see links)
Critical stud thread clearance
Fit studs & gasket
Make studs
Insert 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

Leave the temperature sender hole at 1/8" NPTF - this is the original size thread - although in a different position to before

Rolling road report - visit to Ric Wood on 1st October 2002

Once everything 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.

Driving home 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

Trial fitting - 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 outlined below:

Grind ports to match gasket (only mark out with gasket and studs fitted).
Remove throttle cable clip, then cable...
....HT leads & distributor cap.....
..rocker covers, then inlet manifold complete (8 bolts)
...coolant temp sender wire....
..brake servo hose...
Fit studs to inlet manifold using 2 nuts interlocked
Manifold ready to fit
After 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 end.
First trial fit of the triple carb inlet manifold, not as straightforward as it appears here - see next photo for problem...
...the 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.

...which have 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 item.

Once 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!
The 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!
A 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!
The 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!
After much thought I fabricated the throttle bracket (right), and one for the choke.
The 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 leak!
The 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 another one).
Water take-off problem solved! (See text)
I 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.
Good fit of baseplate demonstrated here
Rough idea of air filter layout