I'm about to start a ej20 set to go onto a ej257 build. I will be relieving the chambers as per previous posts here. Hats off to you FujiK. I've done an old practice set and let me tell you all it is not easy to get the shape around the edges of the valves right. One slip with the die grinder and perfection is lost.
I want to remove all sharp edges from the chambers to help with det while I'm about it. I have a question about the sharp edge along the quench pads. If you have a look at TK's photos on page 7 of this thread you can see what has been done there to blend them out.....but I have some concerns about removing that amount of quench pad area and what effect that might have. Can anyone provide any usefull information regarding this concept?
The 257 heads look to have a little more clearance between the valve and the quench pad but I don't have one here I can measure. I was wondering if some body might be able to measure the distance across the head from pad to pad on a 25 head and post it up so I can get an idea on relative areas Subaru has used between the motors.
What is the purpose of the raised pad around the spark plug. Is that designed for strength, or does it play an important role in how the spark is distributed in the chamber?