Hi Gareth,
I'm new to this but will give you a run down to what I know.
Good gains to be had with porting and polishing the head and I think getting the inlet and outlet flowing better is the best idea. You're doing some improvements to the exhaust which is good and a 4 2 1 manifold is a good choice for a road car. A mild porting job can be done yourself or if you are to go further best to get someone with experience with the engine. One suggestion is to bore the engine to a B20, stick in B20 pistons and put a port and polished B20E head on. The B20E head will give you the gains you're after or if you really want to modify the head go for a B20F head but you shouldn't need to to get 130bhp. I'd suggest bronze valve guides, and good quality stainless exhaust valves with hardened seats for running normal unleaded with a B20E head with the higher compression. If you want you could put in larger inlet valve and deshroud the valves which will increase combustion chamber volume and lower the compression ratio a bit. Best to get a experienced shop to do this.
You can make some improvements with the SU carbs, suggest buying; How to build and power tune SU carburettors and they will do the job for 130bhp.
Regarding the cam, don't discount the standard cam for road use. I'd suggest first decide on what head, carb and exhaust modifications you want to make and then speak to someone about a choice of cam. KG trimning or Sten Parner in Sweden are two companies that have helped me out. Also Simon at Brookhouse is a really helpful guy.
Mitch
|