Dished valves
Posted: April 22nd, 2009, 8:54 pm
Any thoughts about dished valves?
My project is BMW M42 engine (16 valve inline 4 1,8 liter CR 10,0 6800 rpm -> 1,9 liter CR 12,5 8500 rpm) and I could get set of oversize dished valves to quite reasonable price. I know I will lose some CR but I think other aspects will make up for it:
+ waisted valve stem, slightly better flow?
+ better material than stock valves so more durable
+ single piece design, stock valves are two piece welded design which is not good I think
+ 1 mm larger intake/exhaust valve diameter compared to stock
+ lighter than stock so less strain on valvetrain
- slight CR drop, I haven't calculated this yet unfortunately
Is there any pressing reason not to get dished valves on NA engine if you can live with CR drop and would have to otherwise use flat stock valves?
My project is BMW M42 engine (16 valve inline 4 1,8 liter CR 10,0 6800 rpm -> 1,9 liter CR 12,5 8500 rpm) and I could get set of oversize dished valves to quite reasonable price. I know I will lose some CR but I think other aspects will make up for it:
+ waisted valve stem, slightly better flow?
+ better material than stock valves so more durable
+ single piece design, stock valves are two piece welded design which is not good I think
+ 1 mm larger intake/exhaust valve diameter compared to stock
+ lighter than stock so less strain on valvetrain
- slight CR drop, I haven't calculated this yet unfortunately
Is there any pressing reason not to get dished valves on NA engine if you can live with CR drop and would have to otherwise use flat stock valves?