ET: Engine (Twin) hard valve seats

Vincent Brake

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VOC Member
Now ive got me a Hunger Gerät.
To sweeten up a chamber for a new os. Valve seat.
I did that with alu bronze or better AMPCO material.

But now want to work with hard material.
You know of an supplier of a near standard size??
 

roy the mechanic

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S E R D I make the industry standard head/seat machines. Track down a company with one and the seats should be a call away.
 

oexing

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Vincent, my choice was 1.2379 high chrome steel, unhardened shrunk in. That is very durable since ten thousands of kilometers and allright for the Hunger device. But you can easily find lots at Ebay at low price or from Motor Service industry supplies , see below for more info. New standards seem to be sintered seats important for leadfree and liquid gas engines. But 2379 will do for me for life.
With the automatic 45 or 30 degrees feed in the Hunger boring head no valve lapping is required, the very light last cuts are perfect. I swivel the tool bit holder to get sort of multiple correction angles to achieve near radius shape joining the 45 seat, look at last photo.


Vic

Ebay valve seats

scroll down for downloads at
Motorservice

cast iron Ford head machined with Hunger for 2379 steel seats:
DSC00010   kkk.jpg


DSC00011  kkk.jpg


P1060455.JPG


P1060929.JPG
 
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oexing

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VOC Member
Certainly depends on size of head pocket: Say you got 50 mm pocket plus heat the head to min. 200 degrees C and calculate heat extension in this pocket to be able to drop the new ring at no hammer blows . Something around 0,20 mm shrink fit or a bit more. Too lazy to do the maths at the moment. It is 50 mm x 0,000024 x 180 (temp. rise to 200 ) .
The sintered seats are said to need less shrink fit, even no heat in alu heads - if you believe it . . ..

Vic
 

Gerry Clarke

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We used austenitic cast iron for an exhaust valve seat in a Velocette Viper in the early 1980's. Has been very successful, still in there. I think the interference was .004" per inch.

Gerry
 

oexing

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VOC Member
Where did you get that number ? I got the original repair manual with my R 69 S from 1965 . There are all press fits for any engine and gearbox components . So for a 38 mm inlet valve the seat has a shrink fit of 0,20mm , only the smaller 34mm exhaust valve got 0,15 mm shrink fit = 5 thou. That has worked for decades, never dropped a ring. These numbers correlate to the sizes you get when heating the head to min. 200 degrees. So you will be just able to drop the rings in . So same calculated shrink fits were applied to my Vincent heads, wouldn´t want to do a lighter fit. Anyway you have to maintain a certain percentage of shrink fit depending on basic valve sizes, smaller valves less , bigger valves more shrink, so no fixed numbers.
Certain cast iron seat rings were quite allright while leaded fuel was available. But today you have to offer rings that have to operate with diesel, liquid gas, ethanol etc. so no easy task now.

Vic
 
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