This is a summary of cylinder head development work I've been doing and posting on another forum.
I thought these pics of development work I've been doing may be of use to those who have turbocharged 2L 8v engines.
One of the key ways to get high power out these engines is with a good flowing cylinder head. The standard head is not too bad for it's class with reasonable valve sizes as standard and a good downdraft intake port. It's negative points are the dog leg exhaust port and it's emissions friendly open 'D' shaped chamber. The basic chamber is based on the 'bathtub' design which in terms of efficiency is worse than a 'wedge' chamber, which is worse than a 'hemi' head!
Starting with the chamber shape, we can't change the basic 'bathtub' arrangement. So we are limited on how much bigger the valves can go (not much - more on that later). However we can improve the chamber shape by making it a closed chamber. This gives us more squish which improves flame speed and knock resistance. In the US the factory GM turbo version of this engine used a different head casting that had a closed chamber as seen below.
Obviously this is going to be hard to get hold of in the UK. However we can modify the standard chamber and perhaps improve on the closed chamber design that GM used. To do this I looked at modern 2v per cylinder chamber designs. The best of these are to be found on Nascar/Pro-stock engines where considerable time is spent on their design. Most of these engines use 'wedge' chambers forming a figure 8. Some of these though are inclined at quite a shallow angle which then could be copied onto our head. One such design is shown below - a Yates Ford head.
To do this we need to add weld metal to the area above the spark plug and a little opposite. I've marked in pink where the main welding needs to be done above the plug on a stock head.
I have a few heads laying around for development so the above head was used to experiment with. I used MIG (4043 wire, 100% Argon) for the welding process so I could lay down a large amount of weld quickly so the head didn't get too hot. MIG welding aluminium can lead to porous welds though as can be seen from the pics. This is not a problem for just playing with chamber shapes. The final shape would be welded using TIG.
Below is two chambers done with the standard one on the far right.
It needs a little more work particularly opposite the plug - the wall could be brought closer to the valve on the intake side to incourage swirl more.
Once I'm happy with the chamber shapes I'll reproduce them on another head with TIG welding and post more pics. Then it's on to the valves/valve seats and ports!
