[Healeys] valve guides

Sun Mar 29 08:49:06 MDT 2015

Ok Gergo,
We are making progress....
>From your answer I believe that you would concur that both the ID and the
OD of an unrestrained guide would increase as it is heated . i.e. thermal
expansion.
However, you conclude that solids are, to quote, "not that "solid" as they
may look".
>From that statement I presume that you are indicating that the solid
material of the guide distorts or deforms because it is constrained by the
hole in the cylinder head.
Now I would ask you to refer to this video from Purdue University College
of Technology:
https://www.youtube.com/watch?v=V6D3QgdO5Bk
If you are not into the mathematics just skip to 6:45 for the result.
371,000 lbs (168tonnes)!!!
Now check the structural strength of bronze... of course it varies a little
with different alloys but a yield strength of 650 Mpa ( 94274 p.s.i.) is
typical.
The mathematics required to use these numbers to calculate the forces
required to radially crush a cylinder (i.e. our valve guide)  are a little
complex but be assured the numbers are MASSIVE.
So, if the wall of our guide is presumed to have an area of only 600 sq mm.
(0.1 sq in), it would take 4276 kg (9427lbf)to distort or deform it.
Now, armed with that knowledge please read my blog post
<http://www.netbug.net/blogmichael/?p=384> carefully and you may have an
inkling for why I strongly advise against the use of bronze guides in a
cast iron head.

Michael S

On Sun, Mar 29, 2015 at 3:25 AM, Austin Healey <pajtamuvek at gmail.com> wrote:

> Yes. This is happening. The head material expands less, the guide expand
> more, and thus it has to go somewhere. Metals are not that "solid" as they
> might look like.
>
> Gergo
>
> 2015-03-29 4:09 GMT+02:00 Michael Salter <michaelsalter at gmail.com>:
>
>> So Gergo,
>> if I understand you correctly in a situation where the guide was not
>> installed in a head and it was then heated the outside diameter and for
>> that matter the inside diameter of the guide would increase due to thermal
>> expansion....correct?
>> However, the difference, when the guide is installed in the head is that
>> the head material, i.e. the hole that the guide is installed in, would
>> prevent the guide from expanding or, expressed another way, because the
>> hole in the head would not increase in diameter as much as the guide would
>> increase in diameter the head material would effectively compress the guide
>> and prevent it from expanding..... correct?
>>
>> Michael S
>>
>> On Sat, Mar 28, 2015 at 4:38 PM, Austin Healey <pajtamuvek at gmail.com>
>> wrote:
>>
>>> Yes it does. The material has to expand somewhere. It cant go in the
>>> oposite direction.
>>>
>>> g
>>>
>>> 2015-03-28 20:12 GMT+01:00 Michael Salter <michaelsalter at gmail.com>:
>>>
>>>> Hi Gergo,
>>>> just so I'm clear...you are suggesting that the internal diameter of
>>>> the guide will get smaller as it heats up therefore that extra clearance is
>>>> required?
>>>> Michael S
>>>>
>>>> On Sat, Mar 28, 2015 at 3:08 AM, Austin Healey <pajtamuvek at gmail.com>
>>>> wrote:
>>>>
>>>>> Bronze guides expand more when they heat up. Thats why You have to use
>>>>> greater clearance. But when they work, the clearance will be the same. Worn
>>>>> out guides have two negative side effects: oil consumption, and premature
>>>>> wear on the valves as they dissipate heat slower due to rocking on the
>>>>> valve seat. The exhaust guides are more prone to oil consumption, exhaust
>>>>> guides are more prone to overheating.
>>>>>
>>>>> Gergo
>>>>>
>>>>> 2015-03-27 20:01 GMT+01:00 Michael Salter <michaelsalter at gmail.com>:
>>>>>
>>>>>> Hi Raymond,
>>>>>> The factory specification calls for 0.0025 to 0.0015 clearance for
>>>>>> the inlets and 0.002 to 0.001 clearance for the exhausts if you are using
>>>>>> cast iron guides however if you are using bronze THAT WILL NOT WORK!!!
>>>>>> To be safe with bronze guides you will have to hog them out to about
>>>>>> 0.006" clearance..which means there is really no point in replacing them.
>>>>>> I would point you to this article
>>>>>> <http://www.netbug.net/blogmichael/?p=384> on my blog...been there
>>>>>> done that...
>>>>>>
>>>>>> Michael S
>>>>>> BN1 #174
>>>>>>
>>>>>> On Fri, Mar 27, 2015 at 2:17 PM, RAYMOND SMITHSON <rjsmithson at shaw.ca
>>>>>> > wrote:
>>>>>>
>>>>>>> I am rebuilding my 3000 cylinder head and have found the inlet valve
>>>>>>> stems have .008" clearance but the exhaust stems have only .002" clearance.
>>>>>>> Does anyone know if this is common?
>>>>>>>
>>>>>>> _______________________________________________
>>>>>>> Support Team.Net http://www.team.net/donate.html
>>>>>>> Suggested annual donation  $12.75
>>>>>>> Archive: http://www.team.net/archive
>>>>>>> Forums: http://www.team.net/forums
>>>>>>>
>>>>>>> Healeys at autox.team.net
>>>>>>> http://autox.team.net/mailman/listinfo/healeys
>>>>>>>
>>>>>>> Unsubscribe/Manage:
>>>>>>> http://autox.team.net/mailman/options/healeys/michaelsalter@gmail.com
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>
>>>>>>
>>>>>> --
>>>>>> *If you can't fix it with a hammer, you've got an electrical problem.*
>>>>>>
>>>>>>
>>>>>> _______________________________________________
>>>>>> Support Team.Net http://www.team.net/donate.html
>>>>>> Suggested annual donation  $12.75
>>>>>> Archive: http://www.team.net/archive
>>>>>> Forums: http://www.team.net/forums
>>>>>>
>>>>>> Healeys at autox.team.net
>>>>>> http://autox.team.net/mailman/listinfo/healeys
>>>>>>
>>>>>> Unsubscribe/Manage:
>>>>>> http://autox.team.net/mailman/options/healeys/pajtamuvek@gmail.com
>>>>>>
>>>>>>
>>>>>>
>>>>>
>>>>
>>>>
>>>> --
>>>> *If you can't fix it with a hammer, you've got an electrical problem.*
>>>>
>>>>
>>>
>>
>>
>> --
>> *If you can't fix it with a hammer, you've got an electrical problem.*
>>
>>
>

-- 
*If you can't fix it with a hammer, you've got an electrical problem.*
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://autox.team.net/pipermail/healeys/attachments/20150329/1f19e7de/attachment.html>