which octane do I use?

I have a 69 mustang with a 351C. What grade of octane should I use & do
I need to add an additive since we no longer have leaded gas. The
engine is completely overhauled & I have only filled 1 time with the
highest octane.
Thanks nancy m.

nmarlow wrote:
> I have a 69 mustang with a 351C. What grade of octane should I use & do
> I need to add an additive since we no longer have leaded gas. The
> engine is completely overhauled & I have only filled 1 time with the
> highest octane.
> Thanks nancy m.
>

I would run premium gas in it, but the rule of thumb is, use whatever
the lowest is that doesn't cause it to ping under load (accelerating up
an on-ramp, etc.) It depends on how it's tuned, as well.

Do you know if the engine was rebuilt with hardened valve seats? If so,
you won't need lead substitute. If not, which would be odd these days,
you do.

I don't mean to besmirch the regulars here, but there is a better group
in which to ask questions about this car -
alt.hi-po.big-block-ford-mercury. Post this question there. You'll get
advice from a group of seasoned pros.

--
Jason O

"nmarlow" > wrote in message
oups.com...
>I have a 69 mustang with a 351C. What grade of octane should I use & do
> I need to add an additive since we no longer have leaded gas. The
> engine is completely overhauled & I have only filled 1 time with the
> highest octane.
> Thanks nancy m.

My '71 351C 4V M-code runs great on 91 octane which is roughly
equivalent to 99 octane of yesteryear. The timing is set about
12 BTDC and the car never fails to start on the first try even below
freezing. The engine is very responsive. This is California so the gas
may even contain alcohol. In Yosemite last year I paid $3.84/gallon
of high test. But with a car like yours, you don't worry about the price
of gas.

mike

"Jason O" > wrote in message
et...
> nmarlow wrote:
>> I have a 69 mustang with a 351C. What grade of octane should I use & do
>> I need to add an additive since we no longer have leaded gas. The
>> engine is completely overhauled & I have only filled 1 time with the
>> highest octane.
>> Thanks nancy m.
>>
>
> I would run premium gas in it, but the rule of thumb is, use whatever the
> lowest is that doesn't cause it to ping under load (accelerating up an
> on-ramp, etc.) It depends on how it's tuned, as well.
>
> Do you know if the engine was rebuilt with hardened valve seats? If so,
> you won't need lead substitute. If not, which would be odd these days,
> you do.
>
> I don't mean to besmirch the regulars here, but there is a better group in
> which to ask questions about this car - alt.hi-po.big-block-ford-mercury.
> Post this question there. You'll get advice from a group of seasoned
> pros.
>
> --
> Jason O
>


Ya Right, that group of pathetic drunken unemployed alcoholic welfare
queens? Please! Visit alt.hi-po.big-block-ford-mercury only if you want to
argue with a bunch of self absorbed drunks, who's combined hands on
automotive knowledge couldn't get them a job at Jiffy Lube.

You would be much better off leaving Jason O'brien and his group of Butt
Buddies to play with themselves...

With regard to the unleaded fuel issue, the chief concern has been for the
possibility of exhaust valve recession (sink or seat wear) when engines
designed to run on leaded gasoline are operated on unleaded gasoline. If
your engine was completely overhauled recently it may have had hardened
valve seats installed therefore making this is a moot issue.

Typically, most passenger are subjected to service too mild for this issue
to cause problems. The problems typically only occur in older engines when
operating under *sustained* high speeds and loads.

With regard to the octane issue, the easiest answer to your question
regarding the proper octane fuel to use is to use the octane rating as close
as possible to what the manufacturer suggests for the engine. This mindset
assumes you have not made
major modifications to the engine (compression ratio/timing). Since your
engine was completely overhauled recently it may also have had a reduction
of the compression ratio from the original engine design therefore making it
more "friendly' to current premium fuels (91-93 octane).

I am not sure what version of the 351C engine you have since the 351C was
not offered from the factory in the 1969 Mustang model year.

FYI:
2-barrel H-code 351C featured a 9.5:1 compression ratio and a recommended a
minimum fuel octane level of 94
4-barrel M-code 351C featured a 11.0:1 compression ratio and a minimum
recommended fuel octane level of 99.8

Yet another $.02 worth from a proud owner of a 1970 Mach 1 351C M-code
(searches for the highest octane I can find) @
http://community.webshots.com/album/18644819fHAehGJAjt

"nmarlow" > wrote in message
oups.com...
>I have a 69 mustang with a 351C. What grade of octane should I use & do
> I need to add an additive since we no longer have leaded gas. The
> engine is completely overhauled & I have only filled 1 time with the
> highest octane.
> Thanks nancy m.

"Grover C. McCoury III" > wrote in message
...
> With regard to the unleaded fuel issue, the chief concern has been for the
> possibility of exhaust valve recession (sink or seat wear) when engines
> designed to run on leaded gasoline are operated on unleaded gasoline. If
> your engine was completely overhauled recently it may have had hardened
> valve seats installed therefore making this is a moot issue.
>
> Typically, most passenger are subjected to service too mild for this issue
> to cause problems. The problems typically only occur in older engines when
> operating under *sustained* high speeds and loads.
>
> With regard to the octane issue, the easiest answer to your question
> regarding the proper octane fuel to use is to use the octane rating as
> close as possible to what the manufacturer suggests for the engine. This
> mindset assumes you have not made
> major modifications to the engine (compression ratio/timing). Since your
> engine was completely overhauled recently it may also have had a reduction
> of the compression ratio from the original engine design therefore making
> it more "friendly' to current premium fuels (91-93 octane).
>
> I am not sure what version of the 351C engine you have since the 351C was
> not offered from the factory in the 1969 Mustang model year.

My book says the 290/300 HP 351 was offered as an option in '69.
That has to be a Cleveland.


> FYI:
> 2-barrel H-code 351C featured a 9.5:1 compression ratio and a recommended
> a minimum fuel octane level of 94
> 4-barrel M-code 351C featured a 11.0:1 compression ratio and a minimum
> recommended fuel octane level of 99.8

Another way to tell what engine type is to stand on the driver's side of the
engine
accross from the distributor and near the upper left corner of the valve
cover there
is a number stamped, either 2 or 4, and in later years, M.

>
> Yet another $.02 worth from a proud owner of a 1970 Mach 1 351C M-code
> (searches for the highest octane I can find) @
> http://community.webshots.com/album/18644819fHAehGJAjt
>
> "nmarlow" > wrote in message
> oups.com...
>>I have a 69 mustang with a 351C. What grade of octane should I use & do
>> I need to add an additive since we no longer have leaded gas. The
>> engine is completely overhauled & I have only filled 1 time with the
>> highest octane.
>> Thanks nancy m.
>
>

"goodnigh" > wrote in message
link.net...
>
> "Grover C. McCoury III" > wrote in message
> ...
>> With regard to the unleaded fuel issue, the chief concern has been for
>> the possibility of exhaust valve recession (sink or seat wear) when
>> engines designed to run on leaded gasoline are operated on unleaded
>> gasoline. If your engine was completely overhauled recently it may have
>> had hardened valve seats installed therefore making this is a moot issue.
>>
>> Typically, most passenger are subjected to service too mild for this
>> issue to cause problems. The problems typically only occur in older
>> engines when operating under *sustained* high speeds and loads.
>>
>> With regard to the octane issue, the easiest answer to your question
>> regarding the proper octane fuel to use is to use the octane rating as
>> close as possible to what the manufacturer suggests for the engine. This
>> mindset assumes you have not made
>> major modifications to the engine (compression ratio/timing). Since your
>> engine was completely overhauled recently it may also have had a
>> reduction of the compression ratio from the original engine design
>> therefore making it more "friendly' to current premium fuels (91-93
>> octane).
>>
>> I am not sure what version of the 351C engine you have since the 351C was
>> not offered from the factory in the 1969 Mustang model year.
>
> My book says the 290/300 HP 351 was offered as an option in '69.
> That has to be a Cleveland.

FYI: 8-cylinder engines available for the 1969 Mustang are as follows:

302 2V F-code
Boss 302 4V G-code
351W 2V H-code
351W 4V M-code
428 4V CJ Q-code
428 4V CJ Ram Air R-code
390 4V S-code
Boss 429 4V Z-code

Production of the 351C began with the 1970 model year and ended with the
1974 model year.

More information on the Ford 335 series engines (including the 351C) is @
http://www.answers.com/topic/ford-335-engine

Yet another $.02 worth from a proud owner of a 1970 Mach 1 351C 4V M-code @
http://community.webshots.com/album/18644819fHAehGJAjt

>>> I am not sure what version of the 351C engine you have since the 351C
>>> was not offered from the factory in the 1969 Mustang model year.
>>
>> My book says the 290/300 HP 351 was offered as an option in '69.
>> That has to be a Cleveland.
>
> FYI: 8-cylinder engines available for the 1969 Mustang are as follows:
>
> 302 2V F-code
> Boss 302 4V G-code
> 351W 2V H-code
> 351W 4V M-code
> 428 4V CJ Q-code
> 428 4V CJ Ram Air R-code
> 390 4V S-code
> Boss 429 4V Z-code
>
> Production of the 351C began with the 1970 model year and ended with the
> 1974 model year.
>
> More information on the Ford 335 series engines (including the 351C) is @
> http://www.answers.com/topic/ford-335-engine
>
> Yet another $.02 worth from a proud owner of a 1970 Mach 1 351C 4V M-code
> @
> http://community.webshots.com/album/18644819fHAehGJAjt
>

So the M code is simply a 351 4V. Could be Cleveland or Windsor.
Then the only way to tell is to glance at the engine since there
are obvious physical differences between the two.
My '71 is an M code and is clearly a Cleveland.

mike

"goodnigh" > wrote in message
link.net...
>>>> I am not sure what version of the 351C engine you have since the 351C
>>>> was not offered from the factory in the 1969 Mustang model year.
>>>
>>> My book says the 290/300 HP 351 was offered as an option in '69.
>>> That has to be a Cleveland.
>>
>> FYI: 8-cylinder engines available for the 1969 Mustang are as follows:
>>
>> 302 2V F-code
>> Boss 302 4V G-code
>> 351W 2V H-code
>> 351W 4V M-code
>> 428 4V CJ Q-code
>> 428 4V CJ Ram Air R-code
>> 390 4V S-code
>> Boss 429 4V Z-code
>>
>> Production of the 351C began with the 1970 model year and ended with the
>> 1974 model year.
>>
>> More information on the Ford 335 series engines (including the 351C) is @
>> http://www.answers.com/topic/ford-335-engine
>
> So the M code is simply a 351 4V. Could be Cleveland or Windsor.
> Then the only way to tell is to glance at the engine since there
> are obvious physical differences between the two.

The M-code referred to 351 4V CID engines as follows:
1969 - Windsor
1970 - Cleveland
1971 - Cleveland

Quick ways to differentiate the 351W and 351C engines are as follows:
- Coolant passes through the intake manifold of a Windsor engine, not in a
Cleveland (features dry manifold)
- The two bolts holding the fuel pump to the block on a Cleveland engine are
positioned vertical in relationship to each other - on the Windsor the bolts
are positioned horizontally

Yet another $.02 worth from a proud owner of a 1970 Mach 1 351C 4V M-code @
http://community.webshots.com/album/18644819fHAehGJAjt

"Grover C. McCoury III" > wrote in message
...
> "goodnigh" > wrote in message
> link.net...
>>>>> I am not sure what version of the 351C engine you have since the 351C
>>>>> was not offered from the factory in the 1969 Mustang model year.
>>>>
>>>> My book says the 290/300 HP 351 was offered as an option in '69.
>>>> That has to be a Cleveland.
>>>
>>> FYI: 8-cylinder engines available for the 1969 Mustang are as follows:
>>>
>>> 302 2V F-code
>>> Boss 302 4V G-code
>>> 351W 2V H-code
>>> 351W 4V M-code
>>> 428 4V CJ Q-code
>>> 428 4V CJ Ram Air R-code
>>> 390 4V S-code
>>> Boss 429 4V Z-code
>>>
>>> Production of the 351C began with the 1970 model year and ended with the
>>> 1974 model year.
>>>
>>> More information on the Ford 335 series engines (including the 351C) is
>>> @ http://www.answers.com/topic/ford-335-engine
>>
>> So the M code is simply a 351 4V. Could be Cleveland or Windsor.
>> Then the only way to tell is to glance at the engine since there
>> are obvious physical differences between the two.
>
> The M-code referred to 351 4V CID engines as follows:
> 1969 - Windsor
> 1970 - Cleveland
> 1971 - Cleveland
>
> Quick ways to differentiate the 351W and 351C engines are as follows:
> - Coolant passes through the intake manifold of a Windsor engine, not in a
> Cleveland (features dry manifold)
> - The two bolts holding the fuel pump to the block on a Cleveland engine
> are positioned vertical in relationship to each other - on the Windsor the
> bolts are positioned horizontally
>
> Yet another $.02 worth from a proud owner of a 1970 Mach 1 351C 4V M-code
> @ http://community.webshots.com/album/18644819fHAehGJAjt

And the distributor is tilted towards the passenger on the Cleveland along
with large valve covers using 8 bolts and not six as on the Windsor