Jowett Mk2 horizontal engine

[GeoffTParticipant @geofft]

Am currently building the above engine using drawings created by, I think, JasonB. I have a couple of queries I need help with, hopefully from Jason, or anybody who has built this engine.

The valve heads are shown as 2 off at 8mm dia. The bore in the cylinder body for the exhaust is 6mm dia. Should this be 8mm or should 1 valve head be 6mm dia?

Also the inlet valve rod seems too long, by my reckoning I think it should be 86mm overall.

Hope this makes sense!

Geoff

[AStroudParticipant @astroud]

I have built the engine following JB’s plans and both dimensions are correct.

You are drilling and tapping for an M10 plug on the exhaust side so an 8mm valve head will fit into the bore and allow to seal on 6mm bore/valve seat.

The longer inlet valve stem is needed as the valve sits nearer the end of the cylinder than the exhaust to seal on the valve seat on the brass inlet seating

 

[GeoffTParticipant @geofft]

Hi AStroud, thanks for your reply clarifying this.

I have obviously misunderstood the drawings, will have another look.

Geoff

[JasonBModerator @jasonb]

This horizontal section may help.

 

At the top is the exhaust valve which has it’s seat at the bottom of the 9mm dia tapping size hole of the plug thread.

At the bottom you can see a longer valve stem is needed as the valve seats in the screw in adaptor not down inside the cylinder block.

 

[GeoffTParticipant @geofft]

Hi Jason

Yes, that drawing makes it clear, it all makes sense now.

Thanks

Geoff

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