use of multigrade oil in kolher courage and pro v twin engines ?

bertsmobile1

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  • / use of multigrade oil in kolher courage and pro v twin engines ?
cashman, Thank you for finally supporting something I have said for my time on this forum , never confirmed or supported by any user or pro-that the ac mower engines run 280F-300F. So my Beedee oil temp gauge is not lying . My Intek does run at 280f-300F. To me that is really too close to head damaging temps for comfort. (The sump oil is 300F so it is out around the head temp so heat in the head is primarily controlled by the fan?) Especially with the clientele who buy big box , but also others who buy upscale machines with the ac engines it would seem coolers would be beneficial. (cooler oil cools the piston , helping to keep head heat under control?)

As just a homeowner who has often looked upscale it is somewhat puzzling why, at (perhaps) the next step of compact tractors , many seem to retain the same ac engines that have heat problems in the downscale mowers, and do not change over to liquid cooling. The latter engines more expensive to manufacture, I guess.

You have the units a bit mixed up there.
Al-Si-Cu alloys used in die cast heads are safe up tp 400 Deg CENTIGRADE not Farenheit
Thus 320 F is only 120 C which is just inside the temperature range that boils water out of the oil.
You press guides at temperatures around the 250 - 300 C range.
 

motoman

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  • / use of multigrade oil in kolher courage and pro v twin engines ?
We have had this discussion before. I am not a foundry person, but numerous metallurgy forums and sites talk of "creep" in Al alloys around 390F. And head specialists do softness test on car engine heads before they consider milling or guide work. Lots of scrap at these shops where new heads are required.
 

bertsmobile1

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  • / use of multigrade oil in kolher courage and pro v twin engines ?
We have had this discussion before. I am not a foundry person, but numerous metallurgy forums and sites talk of "creep" in Al alloys around 390F. And head specialists do softness test on car engine heads before they consider milling or guide work. Lots of scrap at these shops where new heads are required.

Yes and there is a lot of trash , misquotes and misconceptions that get posted , then reposted then reposted untill they become an undisputed fact, among those who do not know any better.
I can make you a batch of Aluminium that will creep under hot studio lamps or I can make you a batch that you can use to make rockets to propel grenades that are very stable almost up to their melting point of 865 deg C.

If you stop to think about it we make cast aluminium frying pans with electric elements cast into them and most of them run up to 400 deg C.
Although now days they just mark the thermostats 1 to 10.
Good chances your other half has an electric iron to iron your Y fronts.
Again an electric element cast into an aluminum shoe that runs up to around 200 deg C ( linnen setting ) and that surface is intended to remain perfectly flat.

Urban myths come from a fact, like head shops do Brinnels on heads before they do work on them if they think they have been overheated which is quite true.
Then they get applied to all sorts of things that are not applicable just because there is a similarity.
The alloys used for casting air cooled heads are different from the ones used for water cool car heads.
For starters they don't need and Mn or Mg to reduce water corrosion.
These alloys are differnt again to the ones used for marine heads as they don't need to be resistant to salt corrosion regardless of weather they are designed for an open ( salt water ) or closed ( fresh water ) cooling system.
in fact the alloy used for heads on all alloy engines is differnt to the ones used for alloy heads on iron blocks.
We have come a long way since the WWII days of LM -4 ( Light Metal number 4).
The piston inside the engine is also aluminum and according to your logic it should stretch an go to putty inside the engine.
It gets a lot lot lot lot hotter than a head ever will.

The thermal damage that happens to heads is very localised.
It happens around the exhaust valve guide .
This is because the exhaust valve runs at around 700 deg C ( bright red hot ) on a lawnmower and can go up to 900-1200 deg C on high performance car engines with long exhaust duration.
All of this heat has to be dissipated by the valve guide then transferred from the guide to the head
Exhaust valve metallurgy was the limiting factor to developement of higher performance engines again till WWII when research money for aircraft engines was endless.

I am not trying to make this a personnal attack on you but as an ex non- ferrous foundry metallurgist, I can not let misconceptions like this slip past as posts on this forum are searchable and will live a lot longer than you or I can ever hope to.
 

motoman

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  • / use of multigrade oil in kolher courage and pro v twin engines ?
Very persuasive, but I can only respond that I am not convinced about the properties of Al alloy heated to 390F and beyond. The analogy of "mush" is a bit extreme as what appears to happen is a very slight or initial change in the material, not collapse. And maybe we should do a flatness test of frying pans, and a scratch test also. This subject is interesting to me because of pushed guides. Why do they move, and why in an upward direction? I will continue with library research since I do not have direct experience. I also still have the failed Briggs head which I consider having Brinell tested (softness). Wonder what that might show? BTW if no softening takes place why do Briggs (and others) only sell new heads complete to "repair" pushed guides? Glad you responded, but there is always room for dissenting opinions, no? Anyone on this site who is curious should try search words "creep," and "aluminum."
 

bertsmobile1

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  • / use of multigrade oil in kolher courage and pro v twin engines ?
Briggs do that for exactly the same reason why most pistons come fitted with rings.
Sloppy work replacing the damaged guides will make the problem worse.
Also there is a lot more profit in selling you a complete head.

Replacing guides is a highly specialised job requiring a higher degree of skill and understanding than you will find in the average workshop.
Find one with an oven for starters.
Once the guide is out you then have to dress the hole as you will pull some alloy out removing the guide.
Once the hole has been dressed you then need to machine down the replacement guide to .005" to .010" interfearence fit, depending upon guide materialand head material.
Then heat the head, chill the guide and then using the correct insertion tool replace the guide as close to concentric to the seat as possible ( depends upon how accurate you finished the hole ).
Once home, you need to leave it a hour or two to thermally stabilize then recut the seat and dress the valve.

The machining needs to be done very accurately and the whole process will take better than 2 hours depending upon your machining skills and any alignment tooling that you have.
Thus the billable hours alone is greater than the wholesale cost of the new head.

Go to your head shop and have a look at the machinary they use.
I think the cheap Serdi gear come in at about $ 500,000 and is accurate to .0001" because that is the precision required.
The days of doing guides with a blow torch, hammer and punch are long gone.
I do guides in vintage motorcycles and if I could get a new head for $ 1000 I would jump at it rather than $ 25 for a new guide.
Around 10 working hours to do exhaust guides as I get inlets sleeved and machine the valve stem to fit.
 
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