[DeTomaso] Carb and fuel pump

Mon Dec 9 12:05:46 EST 2013

The stock Pantera from 1971 - 1974 would all exceed 130 miles per hour,
what have you  done to it that backed performance up from stock?
I'd look at all the changes first, evaluate what is better and what is not
as good as,  if all the R & R parts are better, perhaps the motor is just
tired,
mis tuned or you have a part in need of replacement.

Michael

On Mon, Dec 9, 2013 at 11:55 AM, Daniel C Jones
<daniel.c.jones2 at gmail.com>wrote:

> > I speculate at 130 MPH, I'm using up all the carb, or all the fuel pump.
>
> Asa,
>
> I ran into a similar problem while tuning the carb on my Triumph TR8 that
> turned out to be a restrictive fuel filter.  I have O2 bungs in the exhaust
> just aft of the header collector and was monitoring the air-fuel ratio with
> a Innovate LM1 wide band oxygen sensor.  My neighbor was driving and in 2nd
> and 3rd, WOT was rich through the RPM band but I noticed 4th would
> eventually
> go very lean at around 110 MPH (around 5500 RPM with my 205/50/15 tires and
> 3.45:1 final drive ratio) and it would stop accelerating.  Hmmm, not good.
> I figured there were 4 possible causes:
>
>  1. Fuel pump capacity insufficient
>  2. Carb inlet needle and seat too small
>  3. Fuel filter too restrictive or clogged
>  4. Sock filter in tank clogged
>
> I wasn't sure about #1 but I doubted it was #2 since past experience had
> shown the stock needle and seat sufficient to support more HP than the
> little 8:1 compression 215 cube V8 was making.  I didn't have a fuel
> pressure
> gauge or regulator hooked up so I went looking for a better fuel filter to
> test.  I found a much larger diameter clear plastic fuel filter (Purolator
> F21111) at a local auto parts store.  It was a bit shorter but had a much
> larger filter area than the clear glass filter the previous owner had
> spliced
> in line.  Since the Purolator filter has a plastic body, I moved it to the
> firewall to keep it away from direct engine heat.  The fuel filter
> originally
> on the car was maybe an inch diameter with a glass body, a metal mesh
> filter
> element and 3/8" inlet and outlet.  I held it up to the light and could see
> through the mesh so it didn't appear clogged.
>
> After installing the filter, I made a few passes shifting out of 4th at
> 5500 RPM and it kept on pulling past 120 MPH in 5th with no signs of going
> lean.  Apparently, the other filter was restricting the pump flow, causing
> the bowls to drain.  With full bowls, I could run it through third before
> they got too low to keep the mixture stable.
>
> Before ditching the carb, I'd go looking for possible fuel or air
> restrictions
> (something like a clogged air filter should go rich).  Welding in an O2
> bung
> and borrowing a wide band O2 sensor will make the diagnostics much easier.
> Also, some Holley carbs have a sintered bronze filter in the inlet
>
> > The LIST 8414 carb I have on my Pantera, was originally released as a
> Ford
> > OEM carb for 351's and 429's.
>
> A vacuum gauge connected to a constant manifold vacuum source will tell you
> if the airflow of the carb is too restrictive.  At the end of a high speed
> WOT run, if reads more than an 1.0" to 1.5", the carb is restrictive.  1.0"
> is good for a high performance street application and 0.7" for more race
> oriented engines.
>
> I'm not familiar with that particular carb but it possible that the carb is
> emissions calibrated and is simply leaning out.  If it's a 4160, you'll
> want
> to convert it to replaceable jets on the secondary side and see if
> richening
> the mixture fixes the problem.
>
> Dan Jones
>
>
> On Sun, Dec 8, 2013 at 2:35 PM, Asa Jay Laughton <asajay at asajay.com>wrote:
>
>>  Hi all,
>>
>> This year (2013) at the Silver State Classic Challenge, I recorded a top
>> speed in the trap of 130.7 MPH.  When I reached the countdown to the trap I
>> was already doing just shy of that to bank time before the Narrows.  I
>> consciously pressed the accelerator a bit more to push her up to a goal 135
>> MPH, but nothing happened.
>>
>> I speculate at 130 MPH, I'm using up all the carb, or all the fuel pump.
>> One, the other, or both.
>>
>> The Carb is a Ford stamped Holley list with these numbers:
>>
>> D8PE-9510-KA
>> LIST 8414
>> 3113
>>
>> This link shows my email back in 1999 with info from Holley that I
>> obtained.
>> http://poca.com/detomaso/1999-09/329.html
>> Apparently it's a 600 cfm.  it has vacuum secondaries and three-quarter
>> turn emission lockouts on the mixture screws.  I've put a standard rebuilt
>> kit through it once or twice.  It's been a really good carb, but I don't
>> know it will pull more than 130 MPH.
>>
>> What to do.
>> As always, money is a bit of an issue.  I'd like to install EFI but
>> that's really expensive.
>> I'd like to keep it responsive at low rpm like she is now, but still have
>> the throughput needed at higher rpm at top speeds.  I think this leans me
>> toward a vacuum secondary rather than mechanical.  I'm sure the cfm needs
>> to be cranked up, but would 650 do it or should I head for 700 or higher?
>>
>> Does anyone have one they'd be willing to part with?
>> Should I send mine into someone like Chuck Nuytten and have them do their
>> magic on it, replacing metering blocks and other mods?
>> Should I just buy a new one?
>>
>> The engine is a 351C bored .030 over, stock stroke.
>> Heads are DOAE, quench chamber.
>> Cam is a Crane hydraulic roller with these specs
>>
>> Intake is an FPP 4145
>> Stock ZF transmission
>>
>> I've got some time so I'm looking for some informed/experienced opinions
>> on what carb would be best.
>>
>> And since Professor Engles from the Midwest Division of the Pantera
>> Research Institute is engaged with Fuel pump questions, I'll just follow
>> his thread on that part. :)
>>
>> Thanks,
>> Asa Jay
>>
>>
>> --
>> Asa Jay Laughton, MSgt, USAFR, Retired
>> & Shelley Marie
>> Spokane, WA
>> ******************************     http://www.racingagainstautism.comhttp://www.teampanteraracing.comhttp://facebook.com/racingagainstautism
>>
>>
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-- 

Michael L. Shortt
Savannah, Georgia
www.michaelshortt.com
michael at michaelshortt.com
912-232-9390

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