Re: Compression

[n9ads@domain.elided (Howard R Pletcher)]

On Mon, 21 Dec 1998 16:56:27 -0800 "Tom Harais" <tjhemh@domain.elided>
writes:
>Dan:
>
>O.K. Howard. I'll bite. How can you have a lower compression engine than
>what IH sent out stock in the U.S. in the first place? i.e. You can't
get
>much lower than what we are already dealing with, short of a 2-stroke or
4
>cycle lawnmower engine.
>
>
Oh you hot-rodders.  Engines can run with less than 10.5:1.  And it's
easy to make a lower ratio on anything.  Just put in 3 head gaskets and
it'll be lower, even starting at 4:1.	:-)

Actually, I think you're asking "why",  not "how".  Go back and check out
the engines of the '20s and '30s.  8:1 would have been considered
outrageous back then. And with the no lead fuels of that time, 8:1 would
not have been workable.  I found a chart showing all farm tractor engines
tested by the Nebraska Testing Labs in 1950 and those engines ranged from
5.5 to 6.5:1with a steady trend upward after that.  Low compression
versions in IH's seemed to be more common through the '50s and '60's for
export use where the gasoline was nowhere near the quality we had in the
states. Even today, don't you have to watch the lower grades in Mexico? 

Low compression seemed to be dieing out in the '70s, although they were
still in the parts catalog so they were still offered.  And it wasn't
only IH that provided lower compression ratings.  The 6 cylinder gaskets
Dan noted would have been the AMC 6-232/258 and I'm sure they didn't make
the low compression versions available just for IH's use.  

My guess is the ratio probably dropped by .5 or less, although I don't
know that I ever saw a figure.

Howard Pletcher
Howteron Products Scout Parts

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