Beta VX modified head & exhaust valves question

Competition engines and 'live' projects only. Good photos to illustrate your post are expected.
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iano
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Joined: June 25th, 2007, 10:13 am
Location: Jimboomba, Australia (A)
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Beta VX modified head & exhaust valves question

Post by iano »

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?
exhaust valve small.jpg
exhaust valve small.jpg (26.8 KiB) Viewed 4179 times
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.....
VX head inlet flow.JPG
VX head inlet flow.JPG (49.23 KiB) Viewed 4178 times
VX exhaust flow.JPG
VX exhaust flow.JPG (21.75 KiB) Viewed 4178 times
VX head inlet side.jpg
VX head inlet side.jpg (202.23 KiB) Viewed 4179 times
Valve seats s.jpg
Valve seats s.jpg (87.65 KiB) Viewed 4179 times
inlet port s.jpg
inlet port s.jpg (65.3 KiB) Viewed 4179 times
inlet valve 2.jpg
inlet valve 2.jpg (81.38 KiB) Viewed 4179 times
Comments appreciated

Regards Ian
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Guy Croft
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Re: Beta VX modified head & exhaust valves question

Post by Guy Croft »

Can't see anything untoward there. But re prep & flow sorry, I am not really prepared to comment publicly on another vendor's work publicly like that. I'd be likely in breach of my own Protocols.

Should have given it to me to do.

G
WhizzMan
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Joined: August 13th, 2010, 8:05 pm
Location: Amsterdam, the Netherlands

Re: Beta VX modified head & exhaust valves question

Post by WhizzMan »

What cam profile, timing and static compression? What RPM? Without those figures, a "BHP figure" is rather nonsensical in my opinion. If anything, it may indicate that it's flowed for a high rev application and may not be suitable for medium rev range street use anymore, due to lack of air speed at lower and medium revs. What sort of porting did you ask for?

Regarding the sodium filling, only the stem is filled and they don't fill it all the way down. I wouldn't worry too much about that. The specs on the photo of your example exhaust valve look more worrying to me. Either it's because of the photo, or the seat area isn't sealing properly because of what appears to be little dents?
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