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ET: Engine (Twin) hard valve seats

Vincent Brake

Well Known and Active Website User
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

Well Known and Active Website User
VOC Member
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

Well Known and Active Website User
VOC Member
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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Vincent Brake

Well Known and Active Website User
VOC Member
What would you divide the diameter for vic? As a interference fit?
400? Or even 300?

Ich habs auf Lager.....
 

oexing

Well Known and Active Website User
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

Active Website User
VOC Member
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

Well Known and Active Website User
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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timetraveller

Well Known and Active Website User
VOC Member
It is a figure I have 'known' for about fifty years and I think that I got it from the original Service Sheets. If I have got that wrong then I apologise and perhaps someone who has access to the original figure could either confirm or correct it. :confused:
 
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timetraveller

Well Known and Active Website User
VOC Member
Thanks Bill, so my remembered figure was not too far out which raises an interesting point. Vincents were not originally known for having valve seats fall out but one of the local owners bought a new cylinder head a few years ago and had the inlet valve seat fall out within very few miles. This was replaced and then it happened again. A few years later the exhaust seat fell out. We wondered at the time whether the aluminium for the cylinder heads was not being heat treated properly. Valve seat materials have had to change a lot since the introduction of lead free seats and I am no longer sure what the expansion coefficients of modern seat materials are. Perhaps Vic, or someone else, with access to modern material specifications would like to comment about what the interference fit should be with modern materials.
 

vibrac

Well Known and Active Website User
VOC Member
I think that a few latter (60-70) IOM efforts had seats drop out (Slater?) so it may have been prevalent under hard conditions back then.
 

greg brillus

Well Known and Active Website User
VOC Member
Heating the cylinder head is an issue as well........aluminium heated to 200 degrees Celsius will anneal the metal which turns it into expensive Plasticine.......... I think some of the earlier Godden heads suffered valve seat failures.
 

peter holmes

Well Known and Active Website User
VOC Member
Surely this information and expertise should be readily available, after all it does not just apply to Vincent cylinder heads, Rolls Royce Merlin Engines were thrashing around our skies 80 years ago, heat treatment of Aluminium and valve seat shrink fits should be a well known science by now , or is the complication simply the reduction or withdrawal of tetraethyl lead being the culprit in this phenomenon.
 

timetraveller

Well Known and Active Website User
VOC Member
The incident I referred to was only about five years ago so not just early Godden heads. Note that the bike referred to is a Comet and only used locally and sedately. No racing, thrashing or other abuse. I was subjected to some criticism for mentioning the incident in MPH but my feeling was that if the seat had fallen out while the rider was in heavy traffic, and the engine had locked solid, he could have ended up under a 40 tonne lorry.
I do remember the problems that Slater had with his IOM efforts. Terry Prince must have got the combination of materials right as his heads tend to be used in anger and do not have this problem.
 

macvette

Well Known and Active Website User
VOC Member
Surely this information and expertise should be readily available, after all it does not just apply to Vincent cylinder heads, Rolls Royce Merlin Engines were thrashing around our skies 80 years ago, heat treatment of Aluminium and valve seat shrink fits should be a well known science by now , or is the complication simply the reduction or withdrawal of tetraethyl lead being the culprit in this phenomenon.
Maughans fitted unleaded seats in my heads so they must know
 

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