Author Topic: Wyvern cylinder head  (Read 885 times)

Offline Phil1965

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Wyvern cylinder head
« on: July 31, 2022, 11:59:10 AM »
Looking for some advice on the valve guides. I have noticed there has been several deviations from the original design for the exhaust guide.
I am contemplating mirroring the inlet valve for the exhaust valve by building up the cylinder mounting flange area with some JB Weld. Having limited experience with this product I would like some thoughts on this prior to committing myself.

Offline michaelr

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Re: Wyvern cylinder head
« Reply #1 on: July 31, 2022, 06:16:12 PM »
I did my exhaust valve pocket the same as the inlet, I didn't have to build up the casting I adjusted the size of the exhaust valve pocket. eg the fixing flange is shaped to fit the position and the valve pocket external length is made to clear the rocker arm and give clearance for adjustment.



« Last Edit: July 31, 2022, 06:45:55 PM by michaelr »

Offline Phil1965

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Re: Wyvern cylinder head
« Reply #2 on: July 31, 2022, 07:04:14 PM »
Thanks for the advice. Did you have any issues sealing the valve pockets?

Offline deltatango

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Re: Wyvern cylinder head
« Reply #3 on: August 01, 2022, 03:04:17 AM »
Hi Phil,
If you haven't already found it I wrote up my Wyvern build in: https://www.modelenginemaker.com/index.php/topic,8733.45.html .

I didn't use the original exhaust valve details with the valve seat made directly in the head casting, and I think that those were intended for a cast iron cylinder head. I couldn't see a valve seat cut in the Al casting that I had lasting very long, particularly for the exhaust. I didn't have to build up anything on the cylinder head with JBW other than some missing bits on the fins.

I made an error when drilling the ports from the valve seats to the outside world and drilled too close to the actual seat. That left the metal too thin and allowed it to distort when tightening into the head; see post #94 in the build log.

I've attached the drawing with the details of the valve gear as I made it as a .pdf. The cylinder head .pdf is too big for the Forum so that is attached as a .jpg.

If you think my drawings would be useful please PM me and I can send them.

David
Don't die wondering!

Offline michaelr

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Re: Wyvern cylinder head
« Reply #4 on: August 01, 2022, 09:07:45 AM »
Thanks for the advice. Did you have any issues sealing the valve pockets?
I did have a problem sealing the valve pockets initially, however I had some very thin section O rings that I fitted over the step on the lower end of the valve pockets, as the valve pocket was tightened down this squeezed the thin O ring to form a thin gasket onto the step machined into the head at the lower end of the valve pocket bore and I got a good seal.

 

 

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