New range of Mangoletsi inlet manifolds

For higher performance classic car conversions for weber & dellorto carburettors & fuel injection throttle bodies

In consultation with our highly experienced and well-known dealers and engine builders, we have analysed the performance requirements for carburettor and manifold conversions for modern classic cars.

In the early days of tuning with Weber and Dellorto twinchoke carburettors, nearly all specialist tuning manifolds for small and medium capacity engines, were only cast to 40mm port size, and many supplied for classic conversions still are;  the exceptions being Mini and MGB, and some large capacity engines, which used 45mm carburettors.

With the continuing development of heads, cams and exhausts, the performance potential of all tuned engines has increased substantially and, in many cases, for high performance, the usual applications are for 45mm, and 48mm carburettors on some larger capacity or very high performance engines.

It must be remembered that you should always choose the smallest carburettor size and manifold that gives you your desired top-end acceleration and speed.  High gas speed in the manifold gives better drivability, economy and much more low- and mid-range torque.

How to select the correct carburettor size and manifold


4242-40 photo

e.g. Part No: 4242-40
Ford Crossflow 1600

With small capacity engines, and larger capacity engines that are  for normal road use, 40mm carburettor are usually the best option. 


4800-45 photo

e.g. Part No: 4800-45
BMW 1600/1800

For smaller capacity engines that are highly tuned, and for larger capacity engines, for fast road use, 45mm carburettors may be an option.  Some of the 45mm manifolds for the early cars in the range were derived from 40mm manifolds.  They were taper bored at the carburettor port end, then ground, opened out and blended to the port, and finally polished.  In establishing the new range, we have selected these manifolds for the smaller capacity engines, and those not usually tuned to the ultimate level of top-end performance.  Using this manifold compared with the 45 Big Bore manifold, the gas speed will be higher, with gains in drivability and low speed torque, and better economy, with little loss of  the top-end performance achievable with the 45 big bore manifold.


4650-45 Big Bore Photo

e.g. Part No: 4650-45 Big Bore
Golf 8-valve GTi

4270-48 Big Bore Photo

e.g. Part No: 4270-48 Big Bore
Ford 2000 OHC

For all high performance applications, and larger engines, we have introduced our new range of “Big-Bore” manifolds for 45mm and 48mm carburettors.  These are cast with the optimum bore sizes from carburettor to the standard cylinder head port dimension.


4030-45 Competition photo

e.g. Part No: 4030-45 Competition
Mini – A type

We are also introducing our engine builders range of “Competition” manifolds, starting with the Mini.  In consultation with leading engine builders, we are producing new manifolds to suit larger cylinder head ports for competition use.  The Competition manifolds are machined at the head port end to match the opened up ports in the cylinder head.  To enable the manifold port position to be matched to the cylinder head, two of the manifold clearance holes are machined to a very close tolerance to two corresponding cylinder head manifold studs – so they effectively acting as dowels.         

Manifold Specifications

All manifolds are supplied with “O” ring blocks, “O” rings, studs (5/16 UNC manifold end / 5/16 UNF nut end), 5/16 UNF Nylok nuts, 5/16 double coil washers.
  • Mangoletsi manifolds are aluminium cast to BS9001 quality standards
  • The carburettor ports are machined centrally to the studs and there are appropriate tapped bosses for servo etc.
  • The bores in all Mangoletsi manifolds are polished.  It is a skilled and labour intensive job and is avoided by many of the specialist manufacturers of cast aluminium manifolds.
There are three main advantages of polished bores:
  • With an “as-cast” finish, the air is more likely to attach to the walls of the manifold, therefore giving a small reduction in flow. Additionally more of the fuel will attach to the walls of the manifold. Cylinder head ports are polished for the same reasons.
  • Manifold carburettor ports are machined centrally in relation to the studs.  In many cases this leaves a ridge. Polishing enables this to be blended out smoothly.
  • Virtually all aftermarket high performance manifolds are sand-cast and with most processes, except with the resin process with which Mangoletsi manifolds are now made, there is a strong possibility of imperfections in the bores.  In extreme cases sand can still be ingrained – polishing ensures removal of these problems.

For those interested in how inlet manifolds are cast, machined and polished, read on!

An inlet manifold casting might appear to be a simple product.  Along with cylinder heads and blocks, it is a product that requires special techniques, very high standard of patterns and tooling, and skill, to give clean, smooth castings with no porosity.

There are three methods of producing aluminium castings:

  • Die-casting, where metal dies are used and the metal poured in to produce a high finish casting.  The cost of the tooling is prohibitive and only appropriate to high volume manufacturer applications.
  • The traditional way of producing castings, going back many centuries, is hand casting in sand, which is very labour intensive, highly skilled and expensive.  The finish is entirely dependent upon the skills of the moulder.  These skills, and the small foundries who relied on them, have now almost entirely disappeared.
  • New resin sand technology has now provided a cost effective way of producing extremely high quality sand castings on a production line.  The draw-back is that the pattern equipment has to be fully mechanised to run on this machinery. 

Due to the continuing interest in modifying classic cars, we have made a very substantial investment in converting all 70 sets of our manifold tooling, so that Mangoletsi Manifolds are now made on the same production line that produces cylinder heads, manifolds and blocks for many motor industry engine manufacturers.

The fundamental requirements for a high performance inlet manifold, are the design, flow, and the quality of the casting, to ensure no porosity (especially if there are water jackets), smooth ports and a high quality external finish.



1.      The ports of the manifold are made by a “core” which is produced by injecting resin sand under pressure into a split core box.


2.      Core making machine – by making a core box with each port core joined the position of the ports to each other is kept very accurate


3.      The patterns are plated and split on the centre line to produce a bottom and top half of the mould.


4.      Moulding process – the resin sand is poured into the pattern assembly and compacted.


5.      Core and mould assembly – The resin sand process produces moulds and cores that are so hard that, when the core is inserted into the mould, it becomes an engineering fit.  This ensures clean castings, as no sand is dislodged into the mould.  Most important is that the position of the ports, relative to each other, and to the casting, stay accurate.  With hand moulding in soft sand, the hand cores can easily be positioned out of location, dislodging sand and misaligning the ports.


6.      The moulds are closed and the metal poured.  Accurate temperature control is critical – too cold and the metal does not flow completely, resulting in porosity – Too hot and excess gas is produced, which cannot escape and so again makes the casting porous.


7.      The castings are fettled, then shot blasted in a highly sophisticated machine. The abrasive qualities of the shot can be varied, along with the blast pressure, giving a consistent external finish.  The manifolds rotate, enabling the blast jets to fully clean the ports.

All the manifold castings are produced to Quality Standard BS9001


Mangolesti manifolds are machined on a specially developed high speed machining station, with a radial arm milling machine and radial arm drilling and tapping machine.





The important feature of the process is that there is only one set up to face, drill and tap the carburettor and head faces, ensuring consistency and accuracy.

  • The manifold is fixed to the tilting table at the correct angle
  • The head face of the manifold is machined at 6000 rpm, ensuring a good finish [fig 1].
  • The jig is fixed centrally to the ports and drilled using the radial arm drill [fig 2]. This ensures stud holes are square to the face and accurate to the ports.
  • The manifold is turned over to the carburettor face and the process repeated.  Again this ensures the carburettor studs are square to the face.

The manifolds then pass into the main machine shop for finishing

First the carburettor face ports are bored centrally to the studs for a perfect match.  Then servo tappings and various machining processes complete the manifold.



The polishing process perfects the manifold.  Normally a very long expensive job, it takes as long to polish a manifold as to machine it, which is why very few companies do it.

With our very fast machining processes, and over 60 years of polishing experience, we can polish all our manifolds and still sell at very competitive prices.


Mangoletsi polished manifolds Logo