# OHC industrial diesels

**URL:** <https://boards.straightdope.com/t/ohc-industrial-diesels/115805>\
**Category:** Factual Questions\
**Created:** [June 25, 2002, 1:16am UTC](https://boards.straightdope.com/t/ohc-industrial-diesels/115805 "2002-06-25T01:16:49Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Enola\_Straight](https://avatars.discourse-cdn.com/v4/letter/e/dec6dc/32.png) [@Enola\_Straight](https://boards.straightdope.com/u/Enola_Straight)\
**Post date:** [June 25, 2002, 1:16am UTC](https://boards.straightdope.com/t/ohc-industrial-diesels/115805/1 "2002-06-25T01:16:49Z")

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Most of todays automotive diesels are over-head cam designs, just like their gasoline counterparts.

However, big industrial diesels…like that in 18 wheelers and generators…are usually of the push-rod type.

I was under the impression that overhead cams provide superior efficiency, and big industrial diesels are engineered to scrape together every smidgen of eficiency economically possible.

So why the discrepancy?

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**Author:** ![Enola\_Straight](https://avatars.discourse-cdn.com/v4/letter/e/dec6dc/32.png) [@Enola\_Straight](https://boards.straightdope.com/u/Enola_Straight)\
**Post date:** [June 26, 2002, 4:04am UTC](https://boards.straightdope.com/t/ohc-industrial-diesels/115805/2 "2002-06-26T04:04:40Z")

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Anthracite?

Anybody?

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**Author:** ![donkeyoatey](https://avatars.discourse-cdn.com/v4/letter/d/e47c2d/32.png) [@donkeyoatey](https://boards.straightdope.com/u/donkeyoatey)\
**Post date:** [June 26, 2002, 5:30am UTC](https://boards.straightdope.com/t/ohc-industrial-diesels/115805/3 "2002-06-26T05:30:46Z")

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From [Caterpillar’s home page](http://www.caterpillar.com/products/engines_n_power_systems/about_engine_division/03_development/development.html):

> [@](#):
>
> …tested on July 3, 1930…An overhead cam, direct injection engine was also developed at that time but was not put into production because of the narrower range of fuels that it would tolerate.

From [Cummins home page](http://www.cummins-sp.com/new_web/co/auto.htm):

> [@](#):
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> Signature 600 Dual overhead camshaft design optimizes high-pressure fuel injection and 600-hp engine braking. High power-to-weight ratio, totally integrated electronics yield high horsepower with high torque ratings.  
> 600 hp
> 
> ISX Combines dual overhead cam design with advanced Interact System technology and integrated engine brake. High efficiency for fleets, high horsepower for owner operators.  
> 400-600 hp

From [Detroit Diesel’s home page](http://www.atlanticdda.com/engines/series_60.cfm):

> [@](#):
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> Equipment Specifications:  
> Overhead Camshaft – This design optimizes intake and exhaust air passages in the cylinder head for easier breathing, and minimizes valve train losses by eliminating the need for push rods.

They do have them now, \*\* Enola Straight\*\*. I think your statement

> [@](#):
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> …are usually of the push-rod type.

is true though, because there are so many old engines still running. 20-30 year old Cat and Cummins 350 and 400 hp. engines are reliable and not uncommon.