Beta VX modified head & exhaust valves question
Posted: April 25th, 2012, 8:55 pm
Dear Guy & forum members,
I have recently had a Beta VX head ported locally which is going to be used on an already modified naturally aspirated Beta 2000cc engine, to replace the current virtually standard Beta 2L carb head.
I noticed that as part of porting the exhaust valves have been back cut, which I would not normally be concerned about, however I believe on the VX they are sodium cooled. This being the case would the back grind weaken the valve structure? I would also appreciate some feedback on the quality of the porting work, not being an expert in this field.....The flow result was 103cfm inlet .420" valve lift, (at 10" depression), with the exhaust flowing 75% of inlet, predicted possible output of 177BHP. This apparently was "before" the inlet guides were reshaped and the SSR was modified slightly to improve the flow around the .300" lift mark where it exhibited a strange drop in flow. After the remedial work was done I was informed the head could produce 192BHP, which seems optimistic to me, so I asked about the 2nd set of flow figures, and was told another full test was not done as they had "fixed" the issue..... Comments appreciated
Regards Ian
I have recently had a Beta VX head ported locally which is going to be used on an already modified naturally aspirated Beta 2000cc engine, to replace the current virtually standard Beta 2L carb head.
I noticed that as part of porting the exhaust valves have been back cut, which I would not normally be concerned about, however I believe on the VX they are sodium cooled. This being the case would the back grind weaken the valve structure? I would also appreciate some feedback on the quality of the porting work, not being an expert in this field.....The flow result was 103cfm inlet .420" valve lift, (at 10" depression), with the exhaust flowing 75% of inlet, predicted possible output of 177BHP. This apparently was "before" the inlet guides were reshaped and the SSR was modified slightly to improve the flow around the .300" lift mark where it exhibited a strange drop in flow. After the remedial work was done I was informed the head could produce 192BHP, which seems optimistic to me, so I asked about the 2nd set of flow figures, and was told another full test was not done as they had "fixed" the issue..... Comments appreciated
Regards Ian