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Re: Oil Viscosity vs Bearing Clearance [Re: dogdays] #2198189
11/17/16 08:21 PM 11/17/16 08:21 PM
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Originally Posted By dogdays
I keep reading about stiffer blocks and cranks. Well, maybe the blocks if going from grey cast (20 million PSI) to nodular or Compacted Graphite (25 to 30 million PSI).

For the cranks, however, if we start out with a standard stock forged crank and change material to 4340, it is maybe 3% stiffer.
When we change the journal size to smaller diameter the crank loses stiffness, it is a natural fact. There is no material that is stiffer than steel that a crank can be made from, except molybdenum, and I don't remember ever seeing molybdenum in its pure form, ready to be cut into a crank. Plus, moly is about 30% more dense than steel.

R.



I wasn't just speaking to hardness, but to overall rigidity in particular. That's why you can take a stock block and put a girdle on it and do very little to overall strength.

Buy an aftermarket back and it it much more rigid and it weighs more.

As far as cranks, the stroke on a PS is relatively short for its displacement. Counter weight placement can make a crank less prone to flex.

Just because you think it won't make it true. Horsepower is KING. To dispute this is stupid. C. Alston
Re: Oil Viscosity vs Bearing Clearance [Re: maximum entropy] #2198192
11/17/16 08:24 PM 11/17/16 08:24 PM
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Originally Posted By maximum entropy
i took some really cool classes in college, and if i remember correctly, the winter number is not a viscosity, but a behavior. it BEHAVES like a 10 weight oil. it equals the lubricating qualities of a 10 weight at the specified temperatures. it was exactly one million years ago tomorrow, so i could be wrong.



All multi grade oils base oil starts as the winter grade.

That is, a 5w30 is a 5 grade oil with viscosity index improvers to make it function like a 30.

Just because you think it won't make it true. Horsepower is KING. To dispute this is stupid. C. Alston
Re: Oil Viscosity vs Bearing Clearance [Re: maximum entropy] #2198423
11/18/16 10:22 AM 11/18/16 10:22 AM
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The W grade indicates that it has met two low temperature viscosity requirements and one high temperature (100 C/212 F) viscosity requirement. SAE J300 sets the standard.
2015 Table here: http://www.widman.biz/English/Tables/J300.html
An article on viscosity standards is here: https://bobistheoilguy.com/putting-the-simple-back-into-viscosity/

"o A 10W-30 Group I mineral oil is basically a SAE 10 that has polymers that expand and cause resistance when heated to flow more slowly, acting as a SAE 30 in hot areas of the engine.
o A 10W-30 Group II oil is similar to the Group I oil except that it is much stronger molecularly and therefore uses fewer polymers.
o A 10W-30 synthetic oil [Group IV or V]is basically a SAE 30 oil that has been created structurally to act as a SAE 10 when it is cold. It does not need polymers."
Richard Widman Selection of the Right Motor Oil for the Corvair and other Engines 24/05/2009 Page 5
Re: Oil Viscosity vs Bearing Clearance [Re: Mattax] #2198447
11/18/16 11:29 AM 11/18/16 11:29 AM
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Where doz the TBN # fit in to all of this, or is it just part of the additive package that addresses alkalinity and has no bearing on viscosity?

Last edited by Crizila; 11/18/16 11:32 AM.
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Re: Oil Viscosity vs Bearing Clearance [Re: Crizila] #2198518
11/18/16 02:27 PM 11/18/16 02:27 PM
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Originally Posted By Crizila
Where doz the TBN # fit in to all of this, or is it just part of the additive package that addresses alkalinity and has no bearing on viscosity?


Depends on who is doing the marketing on TBN. It was a big deal in the early 2000's but that has died down a bunch.

TBN, like most other stuff regarding oil has a purpose. IMHO, it's about the entire package and how well it fits your requirements.

For example, I never ever use a true sytthetic oil with alcohol based fuels.

And, I don't count group III oils as synthetic, even though the US government, through the Supreme Court has said that I should.

Just because you think it won't make it true. Horsepower is KING. To dispute this is stupid. C. Alston
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