This is a B20E head that a good friend of mine ported & the grooves in the combustion chamber are his idea, it’s was done a decade or so ago. I used it on an engine with an enormous cam, 2x 48mm Dellorotos, 4-1 headers, 158mm long conrods, 90.5mm bore & a 77.5mm stroke but I haven’t actually compared it to one of my own street heads that doesn’t have the grooves in the combustion chamber on the same engine. (I’ll get around to it one day, these things take time!)



A lot of metal (brass) is added to the short side radius (inside corner) to improve mid to high lift flow. From outside to inside the floor of the ports now rises 3/8”. On a stock early head, it rises 1/8” & on a late head it rises 1/4” approximately, this is why the 1973+ heads are better to use if you aren’t adding the missing metal.

What the exhaust shortside radius should look like, which isn’t possible without adding metal.


The inside of the inlet port adjacent to the valve seat has no metal removed, nor does the outside corner adjacent to the valve seat. Outboard of the inlet valve, the combustion chamber is widened to the size of a stock head gasket, i.e. 93mm & a convex shape is produced.

What you are looking at here is the largest short side radius on the ports as possible. If you have seen the Lindqvist head, which has raised ports, the effect is to make this short side radius even larger.
Overall, I think this head is ideal for the street because the intake port has very little removed & the exhaust is as good as it gets using a stock 35mm valve. It has stellite inserts too, so it runs fine on unleaded.
IMO, B20E ports are already too large, so if you remove metal that doesn’t result increased air flow, then you loose torque & economy everywhere across the rpm range. The most important part of this & all other heads is actually the valve grind & the ½” each side if the valve seat. If you can’t service your own heads, then you really can’t port your own cylinder head. (You have to learn to walk before you can run).