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Shop temperature for rebuild?

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prima5star Member
Posts: 130
Joined: Thu Oct 06, 2005 5:28 pm
Location: Bay Area, Ca

Temp effects on metals

Post by prima5star » Fri Nov 03, 2006 11:29 am

A little math to give you all a headache!

1 dimensional example to give you the basic idea of the magnitude of the changes going on in the engine.

Elongation = coefficient of thermal expanion * change in temperature * original size of part in 1 direction (this can be a radius etc) Actually, now that I think about it, this should work in 2D and 3D as well...

useful coefficients of thermal expansion on Honda Motorcycles:
aluminum alloys = 13x10^(-6) / degrees F
high strength steel = 8x10^(-6) / degrees F

A 20mm dowel pin in High strength steel is taken from a 35 degree F garage and brought down to a warm 55 degree F basement. When the temperature stabilizes in the pin, what will be the change in length?

Elongation = 8x10^(-6) * (55 - 35) * 20mm = .0032mm

The same pin in Aluminum elongates .0052mm

To put this into perspective, the manufacturers length tolerance for a dowel pin between 12 and 50mm is +/- .75mm, and the manufacturers measuring tolerance for a $100 set of 12" digital calipers is +/- .04mm.

The change in length is both smaller than the manufacturing tolerance and smaller than you can accurately measure. The relative changes in size between different metals is even harder to measure.

Finally, the motorcycles were designed to operate in all sorts of climates, in all seasons, so your temp range is likely right in the middle of what it was designed for.

I don't worry about the colds effects on the engine components, but if I were you, I'd be in that relatively warm basement!

Hope this helps.

Also into Alfa Romeo Giuliettas and Giulias! Looking for a Giulia Super.

FiremanBob Member
Posts: 105
Joined: Sat Oct 28, 2006 7:50 pm
Location: New Hampshire, USA

Shop temperature for rebuild?

Post by FiremanBob » Fri Nov 03, 2006 8:52 pm

Frosty last night - got me wondering if the garage shop at night will be too cold for measuring internal parts and rebuilding the engine. I'm concerned that if I set clearances at say, 40F the motor will be too tight at operating temperature.

Should I bring the engine down into the cellar where it's 55-60 degrees for the re-assembly? Or am I worried about nothing?


4shorts Member
Posts: 436
Joined: Thu Sep 21, 2006 8:45 pm
Location: Newfoundland, Canada

Post by 4shorts » Fri Jan 12, 2007 7:34 am


I've rebuilt many types of engines including Diesels and my rule of thumb is if I don't have to wear gloves during the rebuild I can do the rebuild. It's worked for me the last 25 years or so and I don't plan on changing now! Now that I'm older and not so tough I won't even come out in the shop unless the heat has been on for an hour.

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