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Finely polished Cox .049 with exhaust collector.




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Davis diesel head improvement - Page 2 Empty

Davis diesel head improvement

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Davis diesel head improvement - Page 2 Empty Ever considered using seal machined from PEEK?

Post  AllSoldOut Sat 24 Nov 2018 - 13:56

All,

This is probably a stupid idea, but I would consider getting a seal machined from unfilled PEEK for what is (almost) static sealing application. I appreciate that you might need to change your seal housing design in order to fit it and ten give it the desired 'squeeze'.


If this idea is worth a light and can possibly done, make sure you buy the good stuff - i.e. use a reputable supplier of a manufacturer that processes the bar stock correctly. Back here in the UK I always specify Quadrant Plastics.
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Davis diesel head improvement - Page 2 Empty Re: Davis diesel head improvement

Post  robot797 Sat 24 Nov 2018 - 14:03

could you explain this in diverent words?
i dont realy understand what you mean
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Davis diesel head improvement - Page 2 Empty Re: Davis diesel head improvement

Post  fredvon4 Sun 25 Nov 2018 - 11:41

Had to Google

PEEK or Polyetheretherketone refers to a semi-crystalline organic polymer thermoplastic exhibiting a highly stable chemical structure, which gives it an edge over other materials
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Davis diesel head improvement - Page 2 Empty Re: Davis diesel head improvement

Post  smooth_bill Sun 25 Nov 2018 - 19:58

Don't forget plumbing shop O-rings, as the standard rings last much longer than the original McCoy soft rubber rings. I've been using them in my McCoy .049 diesels for years. Mine use the size 10 rings which are an easy stretch over the McCoy contra pistons, but snap right into the groove, seal very well, and last a long time.

I bought my first McCoy .049 diesel in 1953, and I don't remember seeing O-rings used on any US diesel engines before then. The rings used were soft white rubber and shredded in just a few runs, so the head and contra piston had to be removed regularly to flush out the mush. I called McCoy to order more rings, but they insisted they would send me some just for the asking. The bag they sent lasted far longer than the engine was in my possession.

Bought several McCoy .049 diesels in later years, and haven't worn out any plumbing rings yet.

One precaution I would recommend for any diesel engine, is using care when installing the contra and new ring, so the ring is not damaged during installation.

Bill
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Davis diesel head improvement - Page 2 Empty Re: Davis diesel head improvement

Post  robot797 Tue 4 Dec 2018 - 10:42

okey i got my hardend shaft today
and i ran a engine on a 120ml tank
took over 40 min to drain it
it ran great
and it starts great

i have to change one or 2 things on the drawing and then i am calling it finished
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Davis diesel head improvement - Page 2 Empty Re: Davis diesel head improvement

Post  robot797 Tue 1 Dec 2020 - 14:34

I dont like the latest version of the head
I have been running it for a while now
but there are things I want to improve
wider oring groove
and the concave inside does make the engine run better
so back to the drawing board
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