Replacing Main Bearings in an oven *video

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swooshdave

swooshdave

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The oven method worked just fine. I've used a BBQ before with a Bultaco engine, but a Norton deserves something more elegant.

Next time I might try a heat gun.
 
I haven't had much luck using a heatgun for that purpose. I've tried it several times with various components from cars/bikes with very low percentage of success and have found that the oven method, like you are used in the video, works well. Obviously, larger components might require the kitchen oven (and the wife out of town). ;)
 
I use the top flame plate of my gas stove put the case over it heat up, bearings drop out turn over and drop new ones in, takes less than 5 minutes have done about 20 cases this way.

Ashley
 
MexicoMike said:
I haven't had much luck using a heatgun for that purpose. I've tried it several times with various components from cars/bikes with very low percentage of success and have found that the oven method, like you are used in the video, works well. Obviously, larger components might require the kitchen oven (and the wife out of town). ;)
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Heat gun worked well enough for me as I wasn't able to find a toaster oven large enough to fit the cases, though I employed a low temp-long heat approach... it got the cam bushings out as well

Replacing Main Bearings in an oven *video
 
I used an environmental test chamber at work. A $15'k oven. Fred Eaton puts the case on top of a kerosene space heater in his shop.
 
I think a uniform heat is the most important if you have a choice in the matter.

Fan oven.

Replacing Main Bearings in an oven *video


A long weight to minimise creep on cooling.

Replacing Main Bearings in an oven *video
 
I only drop my old bearing out when I got new ones to drop straight in.

Ashley
 
I used my bbq grill. I monitored the cases' temperatures with a cheap infrared temperature gun. Somewhere around 330f or so, a loud clank announced a successful removal. I used oven mitts to turn over each case in turn and drop in the new bearings. Never having seen it before, I was surprised to see the oil that began bleeding out of the castings.
 
swooshdave said:
I like the weight idea. If you heated evenly I suspect the weight of the bearing would be sufficient.
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It may very well be (bearing weight alone)
The weight (brass) is only for some preload for want of a better word so the bearing remains seated until the engine case bore touches and the interference fit starts, odd things happen when things are cooling.

A fan oven has good air flow so heating would be as uniform as anything else but to get enough expansion to drop a chilled bearing is not much (Compared to removal where the bearing is being heated as well)
I have always liked building engines so there is no hurry.

I think as far as the mains go, anything is better than beating them in cold, but they would probably still last if you did and am willing to bet the factory did just that.
It was obvious when I removed the cam bushes they had been installed cold so the mains were probably no different being a production line.
You can afford to spend a little more time 40+ years later, keep up the good work SD, first fire up must getting closer by the week.
 
I always warm up the bearing to maybe 100 degrees - equal to a hot day in the summer - it gives a little more time to line up the bearing and have it drop right in. The case only need to be in the 230 degree range for R&R bearings.
 
seattle##gs said:
I always warm up the bearing to maybe 100 degrees - equal to a hot day in the summer - it gives a little more time to line up the bearing and have it drop right in. The case only need to be in the 230 degree range for R&R bearings.
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Popping them in the freezer for a few minutes worked great. They dropped in nicely. Why would you warm them up?
 
Someone posted on FB that Ford 9 inch bearing shims can be used on the Norton mains.... Don't shoot the messenger.

If you do add shims, I think the weight is important... fwiw.
 
Time Warp said:
Someone posted on FB that Ford 9 inch bearing shims can be used on the Norton mains.... Don't shoot the messenger.

If you do add shims, I think the weight is important... fwiw.
Click to expand...

Not if you put them between the cases and the bearings.
 
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