[Chrysler300] Fuel for thought

["Rich Barber" <c300@xxxxxxx>]

The recommended Motor Octane Number (MON) for '55 and '56 Chrysler 300's is
85 and 86.5, respectively.  A study of the AMA spec's for the '56 suggests
Chrysler did not go back to the dyno lab to determine the required MON for
the 10.0:1 CR heads.  As noted in the excerpt below, MON is measured
"crudely" in a standard one cylinder engine with variable compression ratio.
Therefore, it is likely the higher CR would require higher MON fuel.  The
flow characteristics of the hemi head certainly help lower required CR for
the hemi engines, but to specify the same MON for the 8.5 CR heads on the
Windsor Poly and the 10.0 CR heads on the 355 Hemi seems illogical, Spock.
My 1955 C-300 seems happy as a clam on 85 "Octane" CA gassamahol, but I have
not tweaked it for maximum dyno performance (yet).  As the note below
states, today's pump octane is the average between Research Octane Number
and Motor Octane Number.  For reference, the hydrocarbon named "octane" has
an octane number of 100.

There is probably no other product we pay so much money for and know so
little about as gasoline.  We pretty much have to have faith in the "system"
that we get a full gallon and that it has the octane number advertised.  And
no one even talks about BTU's per dollar which is what we really need to
make our 300's go up hill.

We drove our '86 Chrysler T&C convertible up into the foothills of the
Sierras today and tanked up on "Premium" 89 octane gas at $4.099/G.  Even
though the 2.2 L engine has a low CR head, its turbo changes everything.  It
does have automatic timing retard if low octane fuel is used and does not
complain, but for full power and boost, I feed it the best available.

I noted the 355 HP package on the '56 B's did not have exhaust heat in the
manifold.  This would result in a slightly cooler fuel air mix entering the
heads.  The race drivers probably did not have to put up with poor cold
engine drivability very long!

Can someone advise the exhaust pipe diameter of the Dodge truck manifolds?
I recall that they are 3".  The AMA specs show an optional 3.0" optional
exhaust pipe for the 300B as of 12-5-55.  Perhaps the truck manifold was
fitted to a few B's from the factory--or maybe only Kiekhaefer knew about
that RPO.

Significance of RON and MON.  Excerpt from:

http://www.refiningonline.com/EngelhardKB/crep/TCR4_29.htm

For clarity it is useful to provide a general overview of an octane number.
An octane number is a quantitative, but imprecise measure of the maximum
compression ratio at which a particular fuel can be utilized in an engine
without some of the fuel /air mixture "knocking" or self igniting. This self
ignition of the air/fuel mixture in the cylinder results in a loss of peak
power. Directionally as the compression ratio of the engine increases so
does the required octane number of the gasoline if engine knocking is to be
avoided.

The performance of an engine is dependent upon many factors, one of which is
the severity of operation. Accordingly the performance of a fuel is also
dependent upon engine severity. To account for differences in the
performance quality of a fuel two engine octane numbers are routinely used.
The Research Octane Number (RON, or F1) simulates fuel performance under low
severity engine operation. The Motor Octane Number (MON, or F2) simulates
more severe operation that might be incurred at high speed or high load. In
practice the octane of a gasoline is reported as the average of RON and MON
or R+M/2.

Classically, both numbers are measured with a standardized single cylinder,
variable compression ratio engine. For both RON and MON, the engine is
operated at a constant speed (RPM's) and the compression ratio is increased
until the onset of knocking. For RON engine speed is set at 600 rpm and MON
is at 900 rpm. 

(Continued at the website...)


-----Original Message-----
From: Chrysler300@xxxxxxxxxxxxxxx [mailto:Chrysler300@xxxxxxxxxxxxxxx] On
Behalf Of RLS
Sent: Tuesday, May 06, 2008 11:39 AM
To: Rich Barber; Chrysler300@xxxxxxxxxxxxxxx; Dan Elliott
Cc: us@xxxxxxxxxx
Subject: Re: [Chrysler300] 1955 AMA Specs (Last update?)

Is there any information on how the 355 hp head was achieved?  Was it a mere
milling of the 340 head, was it a thinner head gasket, WAS there really a
different part number for the 355 head.  My understanding is that the only
other changes for the hp increase was the use of the Dodge truck exhaust
manifolds(I have pair of them) and a larger diameter on the exhaust piping.
Seems to me with a 1 point increase in compression plus the exhaust system
upgrade(and likely carb jetting and ignition timing changes to capitalize on
these changes) that a mere 15 hp change in output sounds a bit conservative.
Would really be of interest to find if any of these old race engines had
dyno runs to measure true hp and how it may have compared to "factory stock"
engines.  As an aside to achieve 139 mph in the flying mile on sand at
Daytona with a car with the aerodynamics of a ship's sail seems quite a
stretch with a 340 hp(gross hp in those days).  I also would be interested
in the rear axle ratios on these flying mile cars(there were several of them
that ran in Daytona in 1956, a number of which exceeded 135 mph is rumored).
With an engine that is pretty much out of rpms at less than 5,500, seems
that a stock 3:54 Powerflite rear axle does not seem likely.   Anyone else
out there with information to chime in?

With the suggested octane levels from 1956, does this mean that one could
run today's regular fuel instead of premium?  I know that there is a
calculation that is made to arrive at today's octane number.  This current
octane number is a combination of the so called "research" and "motor"
numbers in some formula to arrive at today's octane number posted on the
gasoline pumps.

Roger Schaaf
300 B Calyfornua
  ----- Original Message ----- 
  From: Dan Elliott 
  To: Rich Barber ; Chrysler300@xxxxxxxxxxxxxxx 
  Cc: us@xxxxxxxxxx 
  Sent: Tuesday, May 06, 2008 8:19 AM
  Subject: RE: [Chrysler300] 1955 AMA Specs (Last update?)


  Rich, I certainly believe that the AMA specs would have been updated for
the
  1955 300 at least once, to add the three speed manual transmission used in
  NASCAR starting about April 1. Then there would have been a NASCAR
bulletin
  approving the use of the manual trans. I just returned from NASCAR
  archives,
  they don't have alot of that info publically available, so one needs to go
  to private
  sources.

  On a slightly different question, it would be interested to know if the
355
  HP heads
  had any markings on them that are different than the 340 heads. My guess
is
  "NO", but one never can tell. The part numbers were different of course,
  but
  no 300B ever came down the assembly line with 355 HP heads because the
last
  300B was built and shipped before Chrysler dealers were notified that the
  optional
  heads were available. An unanswered question is whether the 355 HP heads
  were
  used in NASCAR, to date no photos have appeared showing a car in actual
  competition
  with 355HP painted on the hood, a NASCAR requirement after it approved the
  use
  of the heads. Photos at ElkHart Lake in August, and Darlington in
September
  both
  show cars with 340HP. Carl K. could have snuck them in, unless he won with
  the
  subsequent teardown, so I'm assuming he didn't. He did sneak in higher
  octane gas,
  which may have been his thinking with the 355 HP heads. But perhaps by the
  time
  they were approved by NASCAR in mid June, someone had gotten onto his
trick
  with the gas, and he couldn't use it anymore. He certainly didn't want any
  disqualifications,
  because Buck Baker was behind Herb Thomas during mid season, until the
  infamous
  crash at the Shelby fairgrounds. So if the 355HP heads were used at all,
  perhaps it
  was after mid September, 1956.

  Dan Elliott

  -----Original Message-----
  From: Chrysler300@xxxxxxxxxxxxxxx [mailto:Chrysler300@xxxxxxxxxxxxxxx]On
  Behalf Of Rich Barber
  Sent: Tuesday, May 06, 2008 12:10 AM
  To: Chrysler300@xxxxxxxxxxxxxxx
  Subject: [Chrysler300] 1955 AMA Specs (Last update?)

  I have been able to obtain a copy of the 1955 AMA Chrysler specs with the
  2-15-55 updated sheets that added the 1955 Chrysler C-300 on that date. I
  find it interesting to note the similarities and differences in the
  Windsor,
  New Yorker and C-300. Imperials are not included. I think they were
  considered to be a separate brand at that time.

  I had been asking about exhaust and tail pipe diameters and find they are
  the same for the '55 NY and C-300. 2" exhaust and 1.8" tailpipe. It is not
  clear as to whether these are OD or ID, but I guess muffler shop guys
  would
  know. I plan to go with 2" and 1-3/4" if those are the standard nominal
  sizes.

  I would appreciate hearing from anyone that has another set of 1955
  Chrysler
  AMA specs as to whether their set shows any further changes were made to
  the
  specs after 2-15-55 during the year. I believe the idle speed of the C-300
  was changed if nothing else.

  Twelve pages of the 1956 AMA specs were published in the most recent Brute
  Force magazine and contained modifications into mid-April, 1956, primarily
  to add the 355 HP engine with 10.0:1 heads. 1956 exhaust pipes for the
  "B's" are shown as 2.25" std, 3.0" optional-probably for the 355's.
  "300-B"
  tailpipes had swollen to 2" in 1956. With the NY tailpipe now spec'd at
  1-3/4".

  I recall seeing a photo of the trunk of a '55 or '56 Kiekhaefer car that
  had
  the tail pipes running across the top of the trunk floor and out the rear
  panel below the trunk lid. Those tail pipes looked huge--3" or 4" and the
  routing avoided the problem of minimal clearance between the rear axle and
  frame and the likelihood of the tail pipe getting damaged or collapsed
  during the race and restricting flow. Probably a NASCAR rule allowed this
  as it would also minimize broken off pieces of tailpipes on the track.

  The standard 354 hemi 300-B engine had 340 HP with 9.0:1 heads. The NY
  also
  had the 9.0:1 heads and 280 HP at 600 fewer RPM and a single 4-barrel.
  86.5
  octane gasoline was specified for all 1956 engines, as compared to 85
  (Motor) octane fuel for all engines in 1955. Anyone know whether that was
  regular or premium "Ethyl" fuel at that time? I think it was regular as I
  remember working in a Clark station that sold only one grade of gas-Clark
  Super 100 and it was lower octane than major brand "Ethyl", but worked
  well
  in most cars of the mid-late '50's.

  C-300'ly,
  Rich Barber
  Brentwood, CA
  1955 Chrysler C-300 (218.6"L x 60.1"H x 79.1"W, 43'-9" turning
  diameter-curb-curb)

  [Non-text portions of this message have been removed]



   

[Non-text portions of this message have been removed]


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