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Old 06-05-2017, 09:13 AM   #1
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Engine classifications: big block vs small block

I have read discussions on big blocks vs small blocks. If the ISB is a small block and an ISX is a big block, at which designation does it go from small block to big block? ISL?
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Old 06-05-2017, 10:41 AM   #2
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Big block diesel engine have a couple different measures. One is the size of the engine which usually starts around 11 liters for a big block or big bore engine. A 6.7/5.9 would be a small block engine and a 8.3/8.9 would be mid-level diesel engine. Within those 3 different engine sizes are horse power and torque. As a general statement most HD big block engines are designed to last over 750K miles.
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Old 06-05-2017, 10:53 AM   #3
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To me ISM and up is "big block" in the CAT lineup it's C-9 and up.
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Old 06-05-2017, 05:06 PM   #4
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Originally Posted by Mr_D View Post
To me ISM and up is "big block" in the CAT lineup it's C-9 and up.
The lines sure have blurred over the years!

As the Cummins ISL is 8.9 and is to me Medium Block Size, I consider the CAT C-9 to be also Medium Block Size!

I consider the Cummins ISC 8.3 to also be Medium Block Size.

I consider the CAT C7 to be at the upper end of the Small Block Size. Along with ISB from 5.9 to whatever the heck size it is now (6.7!) to also be Small Block Size.

I had an old veteran salesman say he always considerer 10L and larger to be BIG BLOCK, like the old CAT C-10.

And you know, it really is just buzzword vocabulary. As what matters as far as pulling ability, is the combo of any give engine in relation to coach weight. Thus the Power To Weight formula is a pretty important item when shopping for a coach. (A bit of a hypocrite with that statement, as I quite often suggest getting the BIGGEST BLOCK ENGINE YOU CAN GET IN A COACH THAT YOU LIKE AND MEETS YOUR NEEDS! I like extra HP/Torque reserves, and I also like as much Braking Horse Power as possible with Jake Compression Brakes (Or Allison Retarder Transmissions. Big blocks do add that above just 'Power to Weight Ratio'!).

Best to all,
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cat, engine

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