Sep 062013

Ropey would be an understatement when describing the plenum chamber. It appears that it was manufactured by bonding two halves together as, once the superficial layers of dirt were removed, cracks were found along the joining lip between the top and bottom halves.

Also, for some unknown reason, a previous owner had drilled a 3/4″ hole in the underside and, looking at it, presumably while blindfolded.

The first thing to do was to remove all the grime and paint in order to make repairs. I was a little bit apprehensive about using strong paint strippers such as Nitromors as I’d heard it damaged fibreglass. Then someone recommended using Fairy Power Spray – I think it’s one of their oven cleaning liquids!

I must admit I was rather sceptical to sat the least. Still, the oven needed cleaning, so if it didn’t work, it wouldn’t be wasted! To my amazement it acted as a very mild paint stripper. Whereas the paint starts to bubble up within a second or two with Nitromors, the Fairy stuff took 5-10 minutes and needed 5-6 applications to remove all the paint.

I guess it shouldn’t have been too much of a surprise as it is designed to cut through oil and grease. The original paint would have been oil based and presumably traces of oil are retained even once the paint has dried.

The air intake brackets were drilled out to provide better access for the repairs or, probably more truthfully, a case of shipwright’s disease. At some stage the brackets must have been painted silver as underneath and in areas that were not visible they were painted black.

I decided to make a fibreglass repair rather than just use filler. The main reason was an attempt to strengthen the join where the two halves had started to come apart, at each side of the opening. The repair sections were built up with three layers of fibreglass which should be sufficient. The mystery hole was also covered over at the same time.

It was then just a case of filling all the various cracks, chips and the repaired hole with Isopon filler before spraying the plenum and air intake bracket with numerous coats of silver Hammerite.

One thing I’ve found with Hammerite paint from painting the wiper motor housing, is that it takes many months to fully harden. Even though it’s dry enough to handle, it’s still quite easy to damage the soft finish for quite some time. Overall I was quite pleased with the end result.

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