Modifying B230 head for big valves

[dkrause]

I am installing "group buy" big valves in a B230-530 head, My engine machinist wants to know if he can safely cut the head back to the "Bore scribe line" to open up the flow? Is there any danger in cutting through the head when he machines this on Exhaust or Intake?

[culberro]

No problem whatsoever.
Make sure the seat throat ID is 86-88% of the valve OD, and don’t sink the valves into the head.

Also, make sure they use bronze guides or guide liners. SS and inconel valves do not like cast iron guides.

[dkrause]

Originally Posted by culberro

No problem whatsoever.
Make sure the seat throat ID is 86-88% of the valve OD, and don’t sink the valves into the head.

Also, make sure they use bronze guides or guide liners. SS and inconel valves do not like cast iron guides.

Thanks just what i wanted to hear, new bronze guides all around, and new oversized seats, I will make sure they don't recess them!

[culberro]

Originally Posted by dkrause

Thanks just what i wanted to hear, new bronze guides all around, and new oversized seats, I will make sure they don't recess them!

No real need for OS seats, as the stock seats work just fine with 2mm+ OS valves.
If they do replace the seats, make sure they are heavy duty seats or you'll be adjusting the valves more frequently. The OEM Volvo seats are REALLY GOOD, and most replacement seats are not nearly the same quality.