Ford: '73 Ford 351c pings - Help Please

Randy <arg> wrote in
news:168.3.44:
 

I read the whole thread. For one thing, that's a '76 carb from the number.
That doesn't necessarily mean anything, but it's not the original carb.

The one thing everybody forgot - your engine was designed to run on 93
octane LEADED gas. There is a HELL of a lot of difference between 93 octane
leaded, and 92 octane unleaded. The engine is starving for octane.

All the rest of the advice is correct. Your carb needs to be rejetted for
your altitude. It's likely jetted lean to run at a higher altitude. I live
at 3500 feet, and my '71 400 runs great here. If I go down to sea level, I
really have to stay out of the gas to keep it from pinging. As mentioned,
the Ford Cleveland engines are notorious pingers, due to the design of the
heads.

Make sure everything is functioning correctly (EGR, vacuum advance, etc.)
No vaccuum leaks (makes it lean).

Back off the timing a few degrees until the pinging stops. You won't lose
power - you will probably gain some. Pinging is a power robber, to say
nothing of the damage it can do.

donutbandit (Leon) wrote: 

snip 
sorry but that is incorrect. 73 was the first year of unleaded only. it
is a unleaded only mtr. (the heads didn`t get hardned valve seats untill 75
though. many problems those couple of years.) KB

"Thundersnake #9 remove spam to reply" <net> wrote in
news:bkq7j5$okt$netins.net:
 

Sorry, but I have to disagree with you. There was no unleaded gasoline and
no unleaded only motors in 1973. The first catalytic converters appeared in
1974. I owned a 1973 California LTD wagon - no cats, no unleaded.

I lived through the period. I remember when unleaded and cats appeared. In
most states, not until 1975, and on certain vehicles, not until much later.

I came from Detriot so I know well that 73 was the last year you got a
"decent" car with leaded gas...now I know I'm old...as the next car I had a 75
Mustang 2 was unleaded...and cat. converter as I almost burnt a field up
parking in it with a hot convertor...BTW - what kind of 73 351 is this ? A car
or truck or what ??? It sounds like you'd need an octane enhancer or even
aviation fuel if you can get it. You will notice a difference. I remember a 6
cyc. Maverick I had in '73....and miss. Linda

com (HbgpodLW) wrote in
news:aol.com:
 

All 351-C 2-V heads from '70-74 were the same. All were medium compression
(9.5-1), made for medium octane leaded gas. In '73, 92 was medium octane,
94 was high octane.

There were no federally mandated unleaded gas engines before 1975.

In 1975, the 351-C engine was discontinued, and the 351-M engine took it's
place, with 8.0-1 compression, hardened valve seats and catalytic
converters all in place.

The person who posted that 1973 351-C engines were unleaded gas engines
simply does not know what he is talking about.

donutbandit wrote:

 

I see some odd assumptions in this post. The first is the assumption that
the head is the determiner in establishing the compresion ratio, as if the
piston had nothing to do with it.

The compression ratio for the 351C-2V engine in 1970 and 1971 was rated at
9.5:1 by Ford. In 1972, that CR rating was lowered to 8.6:1, and it was
lowered again in 1973 to 8:1, where it remained into 1974. The factory
owners manual for my 1973 Montego states:

"All 1973 [Fomoco] engines are designed to
operate on "regular" gasoline with a
research octane rating of at least 91
when the engine is adjusted to factory
recommended specifications".

Today, gasoline is no longer rated simply on the research method, but rather
by the formular R+M/2. Octane ratings taken from a test engine umder load
(the Motor method) generally are lower than the ratings made using a
free-running test engine (the Research method) so that, when averaged, the
resultant rating will be lower than using the research method alone. I do
not know what the straight research rating of 87 R+M/2 octane is, but it
must be close to 91.

A 1973 351C-2V should run comfortably on 87 octane. Certainly, mine does
with a non-stock cam, Holley 600 carb on Performer intake, and dual exhaust
shoving around a heavy car with power accessories and AC in hot near-desert
temps north of LA.

 

I don't recall any small-diameter fuel inlet restrictors until the 1975
model year, and certainly there were no new vehicles with factory cat in
Texas until 1975. Remember the little adapters that allowed you to pump
regular leaded into an unleaded car?
 

Actually, the heads did not have hardened valve seats as we see them from
the machine shop. The valve seat areas of the heads were "induction
hardened" at the factory. Cut the seats a few times, and you go through the
hardened area.
 


Well, maybe he just made a mistake. Maybe you just made a mistake, or maybe
you "don't know what [you] are talking about". Depends on your point of
view, and whether you want to be a part of a newsgroup of folks helping one
another or a bunch of hot heads.

--

Tom
TS3
http://www.geocities.com/styleline58/

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