Once I'd got the 7 on the road and put some miles on the car I became aware my painted cam cover was rubbing against the bonnet in two locations, one very minor spot towards the submarine and wiring exit point from the cover, and a more major spot towards the front offside area.
The image below shows the mess at the front being generated from driving.
Then once cleaned with some quick detailer.
When I spotted this I doubled checked the two bolt mounting points along with the connectors protected by the cam cover, everything seemed fine so I was little stumped by the issue.
Yesterday I decided to take more drastic steps to resolve the problem as I feared long term damage to the alluminum bonnet. I concluded I needed to increase the clearance between the bonnet and cam cover. It wasn't practical to lower the engine or raise the bonnet so I decided to approach the issue by reducing the height of the cover as it sat on top of the engine. The Caterham cam cover is a GRP item and looks to be specifically manufactured for fitment to Duratec powered 7s, so maybe the tolerances in the finishing process weren't that great. Maybe too much GRP had been left causing the extra height.
My plan was simple, shave a few millimetres off the bottom edge and also underneath where the mounting screws are positioned. Having looked at the rubbing locations I didn't expect the contact patch to be that large, and so hoped I needed to remove just a few millimetres.
The cover had a tendency to touch the engine at the front along a curved section, was it possible this was causing the increased height? This seemed likely so I started there, rubbing down with a mixture of wet and dry grades (240 and 320). The process was slow going however it was having the right effect without damaging the paint. I also found I was improving the finish of the bottom edge taking it from a rough unrefined finished to the nice smooth finish you'd expect from fine wet and dry.
Once satisfied with the front I moved to the near side length which sits immediately above the fuel rail. This area also had a tendency to touch the fuel rail. Given the size of this area I opted to use a power file with a fine grit sanding paper instead of the wet and dry by hand. Gentle pressure along the length quickly removed the desired amount but left a course edge which I then again tidied up with wet and dry. To ensure a nice consistent finish I also ran the wet and dry around the remaining lower edge. Lastly I removed a tiny amount underneath each mounting hole being careful not to increase the size of the hole or compromise the strength of the GRP. I'm not sure if this really helped but I felt every millimetre might count.
The cam cover was then cleaned and any sanding residue removed with quick detailer. When I'd removed the cover to address this issue I noticed one of the mounting bolts had gone missing, it's probably vibrated loose and been lost during a drive. The bolts used on the cam cover are low profile pan head which I didn't have however I did find a bolt which seemed to have appropriate clearance, nevertheless, I will source an appropriate pan head replacement.
Having refitted the cam cover the bonnet was immediately fitted to allow assessment of the revised clearance. By gently pressing on the prone areas I concluded the clearance was still insufficient as it took only minor deflection for contact to occur. I still wasn't happy.
I felt removing more GRP wasn't going to fix the issue, and so change tactics. I added a small piece of foam padding to the foam strip already fixed to the nose cone. This approach was designed to lift the bonnet against the nose cone and hopefully provide another millimetre or so of clearance with the cover.
After refitting the bonnet and checking again by gently pressing against the bonnet there was better clearance. Unfortunately the panel gap between bonnet and nose cone now isn't perfect, but then it's no worse than the sides and I'd rather prevent the rubbing.
I'm unsure if the problem is now resolved following these steps as its been raining for the last day or so. Once I know I'll post an update and confirm the outcome.