Tecumseh Valve guide slippage

GaryE

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On my HM-80: while doing a small refurb I found the exhaust valve guide had slipped about 1/8" into the breather area so the exhaust valve won't seat properly.
I tried coaxing it back into position with a C-clamp but it didn't budge and I'm having trouble finding a bigger C-clamp that will fit into the breather.
Any tricks/ideas? Have you heard of this before?
 

motoman

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Gary, Lots of pushed guides here. I always have to preach about it. Anyway the reason IMO: improper press fit dimensions of guide vs bore or overheat approaching 350F + in the guide area/and or bad alloy in the head or failure to heat treat the head at the foundry prior to machine. Unfortunately (on my Intek anyway) mfgrs know there is really no way back once this happens. I disassembled and repositioned the guide . Within an hour it had moved again. Make sure the finned areas of the engine are free of grass or rodent nests. You may have to replace the head assembly.
 

GaryE

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Gary, Lots of pushed guides here. I always have to preach about it. Anyway the reason IMO: improper press fit dimensions of guide vs bore or overheat approaching 350F + in the guide area/and or bad alloy in the head or failure to heat treat the head at the foundry prior to machine. Unfortunately (on my Intek anyway) mfgrs know there is really no way back once this happens. I disassembled and repositioned the guide . Within an hour it had moved again. Make sure the finned areas of the engine are free of grass or rodent nests. You may have to replace the head assembly.

Thank you for the quick response.
I think I've come to the conclusion that the guide is fine and I have a problem with the upper seal which is keeping the spring from seating properly. I'm going to get a new one and see how that works. More to follow.
Thanks again.
 

bertsmobile1

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Gary, Lots of pushed guides here. I always have to preach about it. Anyway the reason IMO: improper press fit dimensions of guide vs bore or overheat approaching 350F + in the guide area

Yes quite likley

bad alloy in the head or failure to heat treat the head at the foundry prior to machine

Not likley.
Alloy heads are not heat treated.
Pressure die casting means the alloy gets mixed better , flows better and rarely goes out of spec as they used SFI ( secondary Foundry Ingot ) which was high in the elements that burn off.
I used to make the ingots we exported to Tecumseh ( and Briggs for that matter )
 

motoman

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Never worked at the foundry but extensive online chatter that typical auto heads are T6 temper which is hard.
 

bertsmobile1

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There is a lot more profit in a car head.
You can get a T6 right from the mould which is what most foundries do.
Heads loose the temper with age and as you have identified soften with over heating.
 
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