Tuesday, September 26, 2006

Cylinder Head Start

I have been far too busy working on the Spitfire recently! Firstly the fuel that was leaking out of the carbs has been stopped! Despite replacing the needles and spacing the fuel pump away from the block with a few gaskets there was still an abundance of leaking petrol. For the time being I have installed a Malapassi Filter King that I bought from my local tuning goodies shop (Midland Performance Centre) where they are always friendly and the prices are keen!

I have also got hold of a cylinder head to port! I missed an ebay auction for one and, when it didn't meet its reserve, I nipped in there with a cheeky offer and got it. I've been getting at it with the grinder ever since it arrived and now I know why getting cylinder heads modified is so expensive! It is very labour intensive work. My intentions are to port match the head to the manifold and to smooth the ports out and finish them with 60 grit paper to promote fuel atomisation. I will polish the exhaust ports and chambers to prevent carbon build up and then I will get 3 angle valve seats done on the valves and seats. At the moment I am dealing with the port around the valve guide which is heavily enclosed by the port (see the pictures). It is still work in progress and it is still far from finished!

Monday, September 11, 2006

Port Matching

I've not had much to do recently on the car and I've just been enjoying using it but recently a problem has reared its ugly head!

I'd been noticing quite a petrol smell when using the car over the last few days but hadn't managed to pin it down until the other day. I suspected the float chambers were leaking petrol but hadn't seen them actually do it until the other day when the right hand carb managed to overflow while I was watching. Having recently had a new fuel pump, I think the increased pressure is overcoming the valves and causing petrol to spill from the overflow. New needle valves have been ordered and I will also try putting a few gaskets between the fuel pump and block to turn the pressure down a bit.

I've also recently started reading a lot about port matching and other cylinder head work. It looks like it'd cost big bucks to get done professionally so I thought why not give it a go at home on an old inlet manifold, then I can get a second hand head and have a go with that! So I started yesterday with the port matching. This boils down to getting the size of the ports on the manifold the same as those on the head. I decided the easiest way to do it would be to enlarge both to the size of the gasket holes. The inlet manifold is already dowled on the Spitfire 1500 so that made life easier to start with. Then I used blue marker around the holes in the manifold where it attaches to the head and fitted the gasket with some bolts through the dowel holes. I could then scribe around the edge of the gasket and see how much material needed removing to bring the manifold holes to just under the size of the gasket holes.

Gradually I have been working the inlet manifold out to the size of the gasket and now I just need to smooth and polish the inside of it as much as possible. Anyway after a few hours with some cutting stones they all looked like this!

Now all I need is a cheap cylinder head of ebay so I can get started on that without worrying too much if it all goes wrong!