Fiddling with my Merlin

by John Winn

Since our touring holiday in France last year I have fiddled a bit with our Merlin.

Engine Bay Cooling Fan

In the July '97 Newsletter I gave the details of fitting an engine bay cooling fan, actually the ventilation fan from a GS Citroen. Well it was happy enough in its motherland but expired on return to the UK. The bearings seized, I think due to the combination of mounting it vertically (to blow the air up past the carb) and being low down on the chassis where it inhaled road dust etc. Its replacement is one of the "hot summer dashboard mounting" fans from the local accessories shop. Being very light I have mounted it on the aluminium inner wing panel adjacent to the carb. It will blow less air but probably enough. I am still uncertain as to whether the fan is worthwhile. However as this year we plan to tour Northern Spain, which sometimes is quite hot, it may prove its worth.

Waterproofing the Boot

A deluge in France showed that my simple approach to sealing the boot by sticking strips of thin upholstery foam around the opening was woefully inadequate. I hunted the catalogues and stalls at shows for something suitable, soft and flexible, fitted a few possibilities but they all let in some water when faced with the garden sprayer rain test. I then looked at draught sealing systems at the local D.I. Y. and now have a system which seems to work well -see sketch, side elevation of top of boot opening


1 Homelux self adhesive foam draught seal -for gaps 1 -3 mm, stuck along the lip on boot body and 2 or 3 " down the sides. 2 Homelux self adhesive PVC "V" shaped draught seal ( for gaps 0.5 -5mm). This comes flat and you make the "V" angle you require. It is stuck to the boot body along the whole top length but leaving a small gap each end for the water ( caught in the "V" which acts like a gutter) to run into the side channels. The "V" should be made so that it will wipe on (touch) the boot lid. The flexible foam strip (1) makes a resilient bed which keeps a generally firm fit and is a secondary protection if some rain gets past the "V".

Electrical ignition

As my only in -depth experience of car mechanics was working on a 1935 Austin 7 as a student in the 1950s my philosophy in building he Merlin was to keep it simple and to avoid electronics. Hence the 2 litre Sierra OHC has a carb and a Cortina MkV Bosch distributor. My son, however, who shoehorned a 4cyl Citroen engine into a 2CV to produce a very naughty motor enthuses about the electronics and built his electronic ignition from a kit. At Christmas, guess what, I received a Velleman Transistor Ignition Kit K2543. This is now built and housed in a small box, which I made from aluminium sheet, overall dims. Of 3" x 2" x 1.75" (including the heat sink) and fixed to the bulkhead in the engine bay adjacent to the battery .It is very neat and uses the points in the distributor to break a very small current which triggers a power transistor. Its virtues are eliminating pitting of the points, which the blurb says should now last 30,000 miles, and a generally improved spark. Being somewhat cautious I have inserted one or two spade connectors in the wiring, for instance to reconnect the condenser, should the electronics ever fail and I need to revert to the original system.

The kit (Ref: K2543) is marketed by Maplin Electronics PLC,PO Box 3, Rayleigh, Essex. SS6 BLR. Tel: 01702 556001 at 12.99 and a mounting box is available at just under 5.00. The instruction book is quite clear and it is a simple build with16 circuit components -also I think surprisingly cheap.

I have now run a few miles with the new system without any problems and I think the tickover is perhaps a little more regular. My son says his car now has an extra usable 500 rpm but he's around that certain age ( thirty years young)! I've settled for the more mature approach and rarely explore above 4,000rpm. ...

Exhaust Manifold Shield

I was checking the plug leads a few months ago and found two had embrittled for an inch or so from the push -on connectors although theoretically protected by the sleeves. The leads were the typical aftermarket blue type, and not Ford. The problem was obviously heat from the manifold which I also thought was not very pretty to look at. I therefore bought a set of Ford leads, orange and with much more substantial sleeves, and fitted a stainless steel deflector -cum -cover plate. The plate is approx. 15.5" x 2.5" cut from a piece 3.5" (see sketch plan) and is mounted flat on the two small tapped pillars which I think used to mount part of the Ford air cleaner. The leads at risk on my manifold are the first 3 as the manifold surrounds these plugs, whereas the plug at the rear of the block is less affected. Therefore I made V- shaped cuts in the in the plate to produce 3 tongues which could be bent to allow the first three plugs to be connected and to provide direct shielding under the sleeves. The end of the plate by the rear plug was bent down over the end of the manifold. Clearance between the plate and the side of the engine was about 5/8". The result is quite pleasing, it smartens up that side of the engine and does a practical job. A tip -I made a couple of prototypes in thin aluminium sheet in order to be confident the design and fit were right before cutting the stainless.


The thickness of the material used was 55thou. Ins. From experience I would now use something thicker as although the shield is quite stiff the overhang beyond the fixing points did occasionally vibrate transiently as the engine passed through a vibration mode, and could be heard. This has bee easily overcome by making a small L shaped bracket mounted upside down on the front manifolds stud and with its "toe" pulling the end of the shield downwards. Alternatively this third mounting point could have been incorporated in the original design.

Sorry we were not at the Donington meeting -we missed the club chats which are always enjoyable. We get enormous pleasure from our Merlin, in fact retirement would be quite incomplete without it. John Winn.

Wiring loom

I bought my loom from Peter and in my enthusiasm for progress never checked which fuse related to which circuit ( and of course no such info came with the loom ).

Has anyone made such a check? My Sierra OHC build, which could have a loom similar to a Cortina build, has two fuse blocks; one in the engine bay has 8 fuses ( 3 x 10, 1 x 2 and 4 x 5 amp) and he other which I have mounted under the passenger side of the dashboard, has 4 fuses ( 1 x 10 and 3 x 5 amp).

May I suggest that if anyone has a fuse location list they let Jenny know for publication in the Newsletter, alternatively let me know direct.

John Winn