[Healeys] valve guides

Sun Mar 29 14:06:04 MDT 2015

My long time friend Dick Paterson runs one of the fastest vintage mini
racers in North America.
Watch him, car #97, in this race at 13.00 mins :
https://www.youtube.com/watch?v=iNRAnvaWguc&list=PLItkgEMb_qyy_NEDpyTjd9c0PIe2vXeHV&index=3
In 2014, after running bronze guides for many years, he had a catastrophic
engine blow up and the cause was traced to the bronze exhaust guides
seizing to the valves.
You could not pay him enough money to change back to bronze guides
today..If it doesn't get you this season it will eventually!!

Michael S
BN1 #174

On Sun, Mar 29, 2015 at 3:20 PM, Austin Healey <pajtamuvek at gmail.com> wrote:

> I am not deep into maths, but have some experience with bronze guides. We
> use them without problems in race mini engines. The key is to use less
> interference fit compared to iron guides. And of course set the system to
> bigger cold clearance.
>
> Gergo
>
> 2015-03-29 17:01 GMT+02:00 Michael Salter <michaelsalter at gmail.com>:
>
>> Oops, small miscalculation there... Where I wrote:
>> *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.*
>> I should have written:
>> *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 6042kg (13,329 lbf) [4276 kg (9427lbf) x
>> 1.414 (root 2)] to distort or deform it. *
>> I think;... because a compression failure would be considered to be a
>> shear failure at 45 degrees.
>> I'm sure there are people out there who are better at these calculations
>> than I am from whom I would welcome comment.
>>
>> Michael S
>> BN1 #174
>>
>> On Sun, Mar 29, 2015 at 10:49 AM, Michael Salter <michaelsalter at gmail.com
>> > wrote:
>>
>>> 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?
>>>>>>>>>>
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>>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> --
>>>>>>>>> *If you can't fix it with a hammer, you've got an electrical
>>>>>>>>> problem.*
>>>>>>>>>
>>>>>>>>>
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>>>>>>>>>
>>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> --
>>>>>>> *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.*
>>>
>>>
>>
>>
>> --
>> *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.*
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