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Crankcase bearings, oven method.


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I have been researching the removal of case bearings using an oven and would like to seek a little more info from others who have used this method.

This is what I have read so far.

Clean the cases.

Preheat the oven to 300F.

Place a biscuit tin on the lower shelf.

Place 1 case on the shelf above, bearing side down.

The aluminium will absorb the heat faster than the bearings and the bearing should drop out onto the lower shelf.

If there are still bearings in the case, remove it from the oven and smack it down onto a wooden board ( with gloves on), and the bearing may fall out.

My question is how long can the case be in the oven before the bearings heat and expand?

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I have been researching the removal of case bearings using an oven and would like to seek a little more info from others who have used this method.

This is what I have read so far.

Clean the cases.

Preheat the oven to 300F.

Place a biscuit tin on the lower shelf.

Place 1 case on the shelf above, bearing side down.

The aluminium will absorb the heat faster than the bearings and the bearing should drop out onto the lower shelf.

If there are still bearings in the case, remove it from the oven and smack it down onto a wooden board ( with gloves on), and the bearing may fall out.

My question is how long can the case be in the oven before the bearings heat and expand?

This technique works well. I usually leave the case in for 15 min

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My BBQ will get hotter than my oven. 🙄

 

The process needs to limit  high heat to the cases; set the oven to a lower temp or limit exposure time.

 

Fact: Aluminum has half the strength at 400F as it does at ambient, and does recover strength on cool down.  I assume the cases are made from the same alloy as the cases so should respond in a similar manner.

 

By limiting exposure time to a few minute the cases will not reach the temp of the oven.

 

RadioShack and others sell infrared sensors that you can use to check case temps.

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put both cases on a cookie sheet. 300F is about the max i would go. normally i only go about 250F and thats generally enough. 15min might be enough time. i have had to go slightly higher on the temp and longer on the time but its a case by case basis as some engines the bearings can be removed with  less heat and time. personally i dont bang them on wood. never have liked that method. i just get a couple 2x4 wood and put a towel or rug or something over them and lay the cases on that after i pull them from the oven. one of the cases youll have to deal with dowel pins so remember that . before hand ill get some appropriate sized sockets and rubber mallet ready and even a blind bearing puller if the situation warrants it. some bearings may have already fallen out but the ones that dont just give a very light tap, if a very light tap doesnt get them out then heat them a bit more. i dont like to heat the cases multiple times so i have the new bearings already frozen and ready to go back in 

 

this is only my way and not necesarrily the only way. hell some guys use a torch which i strongly advise you dont do. after you do a few lower end rebuilds youll find the method you like best

 

 in all the rebuilds ive done, never have all the bearings just fallen out. i suspect this would indicate the cases are extremely hot. probly too hot. or the bearing bore is wallered out and the interference isnt correct any more

Edited by harryhandshake
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