Valve Guide replacement 19.5hp

Boobala

Boobala

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motoman said:
Are you aware of the problem with guides in these air cooled engines? Movement of guide in softened aluminum head (IMO) due to excess heat. In a later ? Briggs Intek 24 you could not buy guides ,only the complete head. My take after trying to reinstall guides with proper .002" press fit, but which moved again? Briggs knows you cannot succeed. I hope your head is an exception. Someone stated there is a loctite formula , but I could not find anything that would live beyond 340F a couple years back. Good luck, just my slant.
Click to expand...

In SOME situations, when trying to get an item "locked into a "bore" (this procedure will work) in this instance you could have the guide "knurled" which will raise the surface material, then you could heat the WHOLE block ( in an oven) and freeze the guide then QUICKLY press the guide into the block .. sort of "shrinking" part A and "enlarging" part B .
 
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Tinkerer200

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motoman said:
Are you aware of the problem with guides in these air cooled engines? Movement of guide in softened aluminum head (IMO) due to excess heat. In a later ? Briggs Intek 24 you could not buy guides ,only the complete head. My take after trying to reinstall guides with proper .002" press fit, but which moved again? Briggs knows you cannot succeed. I hope your head is an exception. Someone stated there is a loctite formula , but I could not find anything that would live beyond 340F a couple years back. Good luck, just my slant.
Click to expand...

Did I miss something here, I thought we were talking about a flat head 42 series horizontally opposed twin. With the 42 series the guides will stay just fine when the proper tools are used to bore and install the guide. An old long time shop will probably have the proper tools.

As for the 24 hp Intek, I have a fix which has been used by dozens over the last 10 years or so with no reports of failure. No need to buy new head.

Walt Conner
wconner5 at frontier dot com
 
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bertsmobile1

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motoman said:
Are you aware of the problem with guides in these air cooled engines? Movement of guide in softened aluminum head (IMO) due to excess heat. In a later ? Briggs Intek 24 you could not buy guides ,only the complete head. My take after trying to reinstall guides with proper .002" press fit, but which moved again? Briggs knows you cannot succeed. I hope your head is an exception. Someone stated there is a loctite formula , but I could not find anything that would live beyond 340F a couple years back. Good luck, just my slant.
Click to expand...

Aluminium -Silicon alloys ( sand castings ) and Aluminium - Silicon - Copper alloys ( pressure die castings ) are all heat treatable.
Any structure than you can create through heat treatment can also be reverted through heat.

So the prolonged over heating of an alloy head can leave it soft.
Done really bad, the entire head can go soft but usually any softening is localised.
Guides can cause softening of the metal around them which will make it difficult to stop them shifting but can be overcome.
If the damage has go progressed far enough to allow the seats to fall out then the head is toast.
Now it can be fixed but that requires heat treatment of the head and that costs more than replacement of the head.
 
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Tinkerer200

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bertsmobile1 said:
Aluminium -Silicon alloys ( sand castings ) and Aluminium - Silicon - Copper alloys ( pressure die castings ) are all heat treatable.
Any structure than you can create through heat treatment can also be reverted through heat.

So the prolonged over heating of an alloy head can leave it soft.
Done really bad, the entire head can go soft but usually any softening is localised.
Guides can cause softening of the metal around them which will make it difficult to stop them shifting but can be overcome.
If the damage has go progressed far enough to allow the seats to fall out then the head is toast.
Now it can be fixed but that requires heat treatment of the head and that costs more than replacement of the head.
Click to expand...

I would say this is extremely rare, in fact, I have never heard of it, maybe it has to do with "down under" ? :>) As I said before, of the dozens AND dozens of people using my fix, I have never heard of a failure. IF someone out there has used my OHV slipped valve guide fix and it failed, Please let us know.

Walt Conner
 
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motoman

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Boobala, The knurling I heard of back in the day was to restore the ID of guide, not the OD for reinsertion. Is that what you mean? BTW the consensus then was that knurling the ID was really not so effective . That process displaced part of the worn ID and forced it to raise, followed by the final reamer pass. If I remember it was often used on guides cut in the base block. I think it was considered a short term fix? I did have a little English 1600 with guides that were metal o-ringed. Can't remember which side, though.

Top level auto repair shops routinely run "scratch tests" or other tests for softness of overheated, liquid cooled, aluminum heads before attempting to repair them. So the notoriously hot-running air cooled engines seem even more prone , whatever the cylinder arrangement.
The big Harley parade bikers go to great lengths to keep the rear cylinder below 300F when moving at lawn tractor speeds.
 
Boobala

Boobala

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motoman said:
Boobala, The knurling I heard of back in the day was to restore the ID of guide, not the OD for reinsertion. Is that what you mean? BTW the consensus then was that knurling the ID was really not so effective . That process displaced part of the worn ID and forced it to raise, followed by the final reamer pass. If I remember it was often used on guides cut in the base block. I think it was considered a short term fix? I did have a little English 1600 with guides that were metal o-ringed. Can't remember which side, though.

Top level auto repair shops routinely run "scratch tests" or other tests for softness of overheated, liquid cooled, aluminum heads before attempting to repair them. So the notoriously hot-running air cooled engines seem even more prone , whatever the cylinder arrangement.
The big Harley parade bikers go to great lengths to keep the rear cylinder below 300F when moving at lawn tractor speeds.
Click to expand...

AS you stated the "knurling" process actually raised the surface area of the item when knurled on the OUTside, hence the necessity to HEAT one part, and FREEZE the knurled part, I don't hear of it anymore, probably because of today's materials and high tech machining ( OLD school )
 
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motoman

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Boobala, Understand, Thanks
 
Boobala

Boobala

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motoman said:
Boobala, Understand, Thanks
Click to expand...

Now you have me wondering what process Briggs use's to install their IRON sleeves in their ALUMINUM blocks..?? ..:rolleyes:
 
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ILENGINE

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From my understanding Boo, the sleeve is installed into the mold and the aluminum is poured around it. Tried to break the block loose from a sleeve a few years ago, and the aluminum is basically welded to the sleeve.
 
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bertsmobile1

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ILENGINE said:
From my understanding Boo, the sleeve is installed into the mold and the aluminum is poured around it. Tried to break the block loose from a sleeve a few years ago, and the aluminum is basically welded to the sleeve.
Click to expand...

Yep,
That is how we did it in our foundry.
All sorts of metal & non metals can be cast in this way.
 
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