535 Bigger valves

[johnwilson]

Has anyone out there machined a 535 head to take bigger valves. If so, what are good valves to go with - 540?

[632 Regal]

NO...do your research here. There are valve companies I can recommend but you have to think about the consequenses such as added weight (will they close) extra rate springs, valve shrouding?? If you put a bigger valve in and it has shrouding performance will drop dramaticly. Piston to valve clearance? might have to cut bigger relief area on the pistons too. Also you have to relate intake to exhaust flow rates and characteristics, if you have 10% more flow on the exhaust do you have an extra 20% intake? Etc etc etc etc...blah blah blah...if you want to do it make sure you want to do it, these heads flow as good as motorcycle heads out of the box, I dont think you will be able to justify bigger valves unless you have some special intention...also how much room is there between the valves right now?

[Bill R.]

valves

Has anyone out there machined a 535 head to take bigger valves. If so, what are good valves to go with - 540?

[Jose]

Total waste of money. We tried fitting bigger valves on the turbo M30 engine in a E28 but it amounted to no increase at all. It would be only of use to change these valves by lighter ones if you would be upgrading the whole head and bottom to race spec. If not don' t bother. Just polish your current valves and decarbonize the head and it will feel like a new motor.