The valve seats have a 2 angle job on both intake and exhaust. This is a really nice touch and does improve performance. A radius cut has been made on the chamber walls surrounding the valves to reduce shrouding. The combustion chambers have been machined (approximately) down to the level of the valve seat top cut in the area between the valve seats. Harmonics and spring walk are also likely to be a problem. There is 4mm (or more) of slop in the exhaust retainers and a little less on the intake retainers. If my machinist presented me with work like that I would find a new machinist. Standard retainers are used, and the springs are a very poor fit into them. They felt stiffer than factory springs when I was removing them. The valve springs are single with a flat wound damper.
#Yella terra rockers ford 200 series#
They have undercut stems and judging by the part number, are from the Ferrea 5000 series of street performance valves. The intake and exhaust valves are Ferrea single piece stainless with a Yella Terra part number. It is much sharper than a standard casting due to the larger valve and bowl diameter. Unfortunately the short side radius lets the intake work down. The transition from the fresh cut to the original bowls is generally quite nice without excessive ridges or sharp angles. Intake bowls have been plunge cut (throated out) to accomodate the larger intake valves. There is a ridge between some machined and un-machined surfaces. The machining goes a maximum of about 15mm into the port, some are much less and some are untouched. It is so slight that not all ports were touched on both sides. Intake ports have a slight machining on the sides of the port. Number 4 rod did not match the others (no SPS bolts, just the standard ones) so the engine may have been apart previously, or it may have been incorrectly assembled at Tickford. These modifications are what this set has. So now that I have a nice clean set in my workshop I will describe what I can see has been changed from a standard GT40P casting which I also have right along side. I thought it might be a good idea to document what modifications Tickford has done to the 220kW heads.