This car was already running an aftermarket air filter with a heat shield partition that sealed against the bonnet when closed - but having a full cover makes it street legal and avoids hassles.

It’s made from 1.6mm aluminium sheet, and attaches to the existing partition and a headlight bolt. There is also a hole for the air filter mounting, replacing the original bracket.

Here’s a photo from a nice angle. The Silvia on the left is waiting for an engine and a few other jobs, and will hopefully be on the road soon!

I’ve done a few airboxes for people with exposed “pod” filters - for legality reasons as well as keeping the hot engine bay air out of the engine’s intake.

This one was a bit different because the MX-5’s engine bay is much tighter for space - especially when it has a turbo conversion and a big strut brace across the middle!

I started making up the usual sheet aluminium box, but found that there is not enough width between the headlight motor and the strut tower to fit the filter.

I’ve seen long thin air filters that would do the job, but was unable to source one, so started looking at other options.

The end result was an all stainless steel conical casing that clips on over a base plate, with a 3″ inlet pipe welded in the top. I think it turned out pretty neat, and it matches the rest of the engine bay pretty well.

It’s also easy to service which is nice

“pod” filters are popular on modified cars - for better air flow into the engine and increased power.

Legally though, for a street car the air filter needs to be enclosed, and it’s good to shield the intake from the hot air in the engine bay.

For this one I made a two piece box with a plate sealing off the filter area from the engine bay, then a flat cover that slides under the edge of the front guard and screws down to the side plate.

I tend to prefer factory engines, even with relatively high k’s on them, than rebuilt engines - and this is the reason for that!

The car’s owner had the engine rebuilt, but it failed shortly after. It was repaired under warranty but wasn’t cleaned out properly, so metal filings then clogged up oil feeds and damaged other parts - including the turbo.

It’s been a bit of an ongoing saga - and after yet another repair it lasted a short time before making nasty noises from the top end of the engine.

I had a quick look and found two problems.

One was that the oil spray bar on the camshaft (visible through the oil filler hole) was not spraying oil - which usually means it’s clogged up with gunk from the engine.

The other problem, which is a bit of a worry, was that the remotely mounted oil filter had been plumbed in backwards! The filter has an anti drain back valve, so when it’s backwards it will block the oil flow - causing the relief valve in the engine to bypass the filter.

So, an engine likely to be full of metal filings had been running with no oil filtration!

After removing the cam cover, it was obvious that there was some damage to the cams due to the lack of oil - which was the cause of the noise.

It’s a bit saddening to see this happen to a brand new set of cams!

The engine really needs another teardown, inspection, and very thorough cleanup.