I have a Ford 1973 Ranchero GT (351c (rebuilt), 4-bbl) which I have had
for about two years now. During this time I've had three full tune-ups
performed from two different establishments. The most recent tune-up was
performed just before I left to go on a trip to the mountains not that
The motor pings bad at sea level during high acceleration or going up
the local hills. Yet runs surprisingly strong at an altitude of 6-7000
The power curve seems to dip the lowest at around 2-3000 feet. It was
just chuuuuugging on the freeway at about 40MPH as I kept my foot off
the gas (something I don't have to do on the freeway at sea level) to
prevent the motor from pinging going up a slight grade...
Forming a check-mark shaped power curve in the process.
None of the previous full tune-ups have stopped the pinging at sea level
and this was the first trip with the truck at these higher altitudes. So
I was surprised at the performance and lack of pinging. It must in part
have something to do with the thin oxygen at higher altitudes.
I have the original 1973 Ranchero owners manual and the manual says that
93 octane fuel should be used. The best found around here these days is
92 octane. I can't imagine that one octane level is the problem.
Especially since I used 92 octane throughout the entire trip.
I was told by one tune-up place that pinging was a problem with Ford
motors of this size during the early 1970s and I don't want to live at
6-7000 feet just to have a vehicle that doesn't ping. Hehe
Someone else suggested I looked on AllData. The closest match from the
Automotive Recalls and Technical Service Bulletins were for a 1973 Ford
Truck Ranchero V8-351 VIN Q 4-bbl. The TSBs are:
TSB Number Issue Date TSB Title
ATRATB024 SEP 90 A/T - Harsh Reverse Engagements
ATRATB8761 NOV 87 A/T - C6 No. 9 Thrust Washer Failure
ATRATB8658 NOV 86 A/T - Slipping Or No Third Gear After Overhaul
ATRASIL8519 JAN 85 A/T - Modulator Chart
ATRATB8543 JAN 85 A/T - Recurrent Sticking Valves/In Line Filters
8211A1 JUN 82 High Altitude Adjustments
I'm wondering if the last one, the "High Altitude Adjustments", has
anything to do with the pinging? Maybe in a reverse sort of way?
There are no links at the site and I have repeatedly looked for the
"High Altitude Adjustments" without much luck. It is just a wild guess
that it has anything at all to do with the pinging.
Interestingly, when checking out other Ford vehicle of the same year at
AllData, they all seem to have "High Altitude Adjustments" listed in
What are "High Altitude Adjustments"? How does it get adjusted? Is this
even the problem?
Is this the fuel mixture on the carburetor? To my knowledge, the fuel
mixture would either lean or rich the fuel coming out of the carburetor
at idle and not limit the amount of air. Perhaps I could just let the
air cleaner get dirty? Well, it's what happens when you are at your wits
Could someone /please/ offer some advice?
Absent vacuum leaks -
Sounds to me like the Adjustments were made to this particular carburetor.
The mixture is controlled by the main metering jets, not screw adjustment.
Those you presently run may be too small.
Depends on Carb. Does yours have the "power valve"?
Look here, read between lines (not on main subject)...
but on re-reading your post, you seem to say that it would ping on tip-in.
That means slight acceleration.. that true?
If so, that's your main jets... can you disable the secondary? When you do
does it still have the problem?
I LOVE EECIV
Hi Backyard Mechanic,
On Sep 07 2003, Backyard Mechanic wrote:
The description doesn't fit. For example:
"Your Holley-carbureted street car idles terribly"
Nope, smooth as silk.
"has taken to fouling spark plugs every week or so"
Nope, they're light-tan.
"the gas mileage absolutely sucks"
Its an old truck, it's suppose to suck. :) If I keep my foot off the
pelt, I can get about 16 on the freeway.
"theres an ominous black cloud swirling from your exhaust"
Nope, white and watery.
"If any of these descriptions fit your Holley carb-equipped street or
race car, you probably have a blown power valve."
Thanks for the info, but it seems unlikely that this is the problem.
It pings during high acceleration or going up the local hills. Just not
at high altitude.
The high acceleration is usually getting on the freeway or making a left
turn across traffic without a light to assist.
One local street which goes straight up to the top of a hill is quite
steep and long. If I floor at the base I can maintain 3rd gear for about a
quarter of the distance then it pings, 2nd for about 1/2 the overall
distance then it pings, and near the top (last quarter and steepest) 1st
gear @ 3000 RRM (it has a factory tech in the dash) doing about 10-15 MPH.
When I mention a hill, I'm thinking of 1000 feet high or less.
I'm not sure.
Electronic Engine Control (Version IV)
The only thing electronic is the coil and points. :)
Hi Backyard Mechanic,
On Sep 07 2003, Backyard Mechanic wrote:
Good point, I hadn't thought of that, but I'm fairly sure that I didn't
missed any of the hoses when I was attaching them. It's possible that
there might I might have missed a small hole.
Hmm, I could go around the top of the Intake Manifold and spray
something and see if it gets sucked in and the engine speeds up. Would
Berryman B-12 be enough to do that? Or is there something better?
I'm not sure what those would be and I'm not sure if the carburetor is
stock to the vehicle. More below.
Ah, right. Sounds like a random process if this is the problem locating
the correct size jet.
Would that be because up in the higher altitude the less air mixes
better with the smaller amount of gas? In other words, at sea leave, I'm
not placing enough gas into the engine to match the greater amount of
But I'm not sure how that would effect the mid-range, the 2-3000 feet
power drop. I suppose it is possible that it could be a coincidence and
there is something else the matter.
The carburetor has the tag from Motorcraft, it reads:
I've looked for what the numbers mean over at Motorcraft as well as
other places and the D6PE doesn't exist. The best guess is that this is
a carburetor from 1976 (D6), but the PE doesn't match.
As near as I can tell it is either the 4300 or the 4350 based on the
Idle Speed Adjustment (ISA) for these reasons:
1) The ISA is not just a screw (by itself) which when turned moves the
2) The ISA is not a screw located at the end of the solenoid which would
extend the solenoid armature into the Throttle Lever.
3) The ISA is not adjusted by rotating the entire solenoid body into a
threaded bracket pushing it into the Throttle Lever.
Instead, the ISA works by a U shaped bracket mounted on the Intake
Manifold. The U shaped bracket has a long screw which is threaded from
one end to the other long-wise. Attached in the middle of the screw
threads is another U shaped bracket. This one is smaller, upside down
and has the solenoid mounted on it. When the screw at the end of the U
shaped bracket is turned, it positions the entire solenoid into and away
from the Throttle Lever. Like so:
Direction of Solenoid Movement -->
| |==== ||
Turn `-|--|-' ||
Here | | | | \\
`--> *+-----+--+----| \\
| | ||
I don't know how standard this setup was back then. The other thing the
carburetor has is a square hole on top.
1. You're beyond my level of expertise... and, quite frankly, interest. I
hated carbs in the 60's, I hate them now.
- I prolly shouldnt even have got into this
2. Read what WLTom wrote.. I blush to think that I forgot to tell you to make
sure you have close to spec timing setup.
3. What do your plugs say?
All right, sounds dead stock.
Clevelands with open chambered heads have a tendancy to ping when under
load. There is just a whole lotta area in there for the flame front to
travel over. It has to travel very fast, and it's more dilute. The
closed-chambered heads, by comparison, are more detonation resistant, even
with higher compression ratios.
With age, carbon builds up and creates hot spots; little glow plugs.
Today's gas does not help. A flush of some sort might help, but I can not
say for sure if dirty combustion chambers is your problem.
You can reduce the pinging simply by retarding the timing a couple of
degrees. This may be all that you need. I would also be inclined to richen
slightly the power enrichment circuit, but I play with AFBs and Holleys. I
am afraid I can offer no advice on how to tune the Motorcraft carb. I run
my 351C (2V heads, Performer intake, slight cam, '73 Montego) with about 10
degrees initial, and use manifold vacuum to the dizz with the vacuum advance
limited to 10 degrees above mechanical. This is not factory, but the vacuum
advance collapses much more quickly when you push into the throttle than
ported vacuum does, reducing pinging when merging or climbing hills. I run
mine on 87.
I hope something here is of help to you. While you are seeking info, visit
the Cleveland forum. Someone there might have some Motorcraft tuning
If the motor is stock internally (no high compression pistons or different
cam) get a book that shows the distributor advance curve. Then check it with
a timing light and tachometer. Older Fords are easy to recurve by changing
the springs in the mechanical advance. There were also vacuum advance units
that were adjustable (they used an allen wrench slipped into the tube that
the vacuum hose attaches to). You may have a different distributor also.
Some Fords came with a dual vacuum distributor, with two hoses, one for
advance and one for retard, but even those with the dual vacuum didn't
always use the retard. It depended on the application.
Pinging is more often from the advance curve than from the carb. Or just
from too much advance. With lots of miles on it, one easy way to set the
timing is to gradually increase the base timing until it pings, then back it
off about 2 degrees. Being an older car, the vibration damper may have
slipped a bit, which could cause problems when setting the timing with a
timing light. I had a 58 Buick that ran about 35 degrees initial advance
when measured with a timing light. I set it by ear and it ran fine until I
sold it with 220,000 miles for that very reason.
Carbon buildup is a possibility, but that isn't a common problem.
If it runs well apart from the pinging, without hesitation or black exhaust
smoke, and good acceleration, it probably isn't the carb. If the EGR
passages are clogged, it will run a little hot, which can cause pinging. The
EGR isd used to lower combustion temperatures to reduce NOX emissions. (I
think it's NOX, anyway) If it passes smog with no problems, there probably
isn't a whole lot wrong with it outside of minor adjustments.
Every day is a good day- it's just that some are better than others.
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
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.
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
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.
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
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
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.
Yep I got that mistake thing going on for sure!!!!!!! 73 was the first year
of the ugly 5mph bumpers. (my thoughts) and EGR valves.75 was the unleaded
fuel only with cat cars. We did have major valve guide problems in 73-74 due
to emission controls just added on and not designed in. I pulled many a head
under warrenty then to replace guides. (more the 302-351w than the others
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