<div dir="ltr">> I speculate at 130 MPH, I'm using up all the carb, or all the fuel pump.<br><br>Asa,<br><br>I ran into a similar problem while tuning the carb on my Triumph TR8 that<br>turned out to be a restrictive fuel filter. I have O2 bungs in the exhaust<br>
just aft of the header collector and was monitoring the air-fuel ratio with<br>a Innovate LM1 wide band oxygen sensor. My neighbor was driving and in 2nd<br>and 3rd, WOT was rich through the RPM band but I noticed 4th would eventually<br>
go very lean at around 110 MPH (around 5500 RPM with my 205/50/15 tires and<br>3.45:1 final drive ratio) and it would stop accelerating. Hmmm, not good.<br>I figured there were 4 possible causes:<br><br> 1. Fuel pump capacity insufficient<br>
2. Carb inlet needle and seat too small<br> 3. Fuel filter too restrictive or clogged<br> 4. Sock filter in tank clogged<br><br>I wasn't sure about #1 but I doubted it was #2 since past experience had<br>shown the stock needle and seat sufficient to support more HP than the<br>
little 8:1 compression 215 cube V8 was making. I didn't have a fuel pressure<br>gauge or regulator hooked up so I went looking for a better fuel filter to<br>test. I found a much larger diameter clear plastic fuel filter (Purolator<br>
F21111) at a local auto parts store. It was a bit shorter but had a much<br>larger filter area than the clear glass filter the previous owner had spliced<br>in line. Since the Purolator filter has a plastic body, I moved it to the<br>
firewall to keep it away from direct engine heat. The fuel filter originally<br>on the car was maybe an inch diameter with a glass body, a metal mesh filter<br>element and 3/8" inlet and outlet. I held it up to the light and could see<br>
through the mesh so it didn't appear clogged.<br><br>After installing the filter, I made a few passes shifting out of 4th at<br>5500 RPM and it kept on pulling past 120 MPH in 5th with no signs of going<br>lean. Apparently, the other filter was restricting the pump flow, causing<br>
the bowls to drain. With full bowls, I could run it through third before<br>they got too low to keep the mixture stable.<br><br>Before ditching the carb, I'd go looking for possible fuel or air restrictions<br>(something like a clogged air filter should go rich). Welding in an O2 bung<br>
and borrowing a wide band O2 sensor will make the diagnostics much easier.<br>Also, some Holley carbs have a sintered bronze filter in the inlet<br><br>> The LIST 8414 carb I have on my Pantera, was originally released as a Ford<br>
> OEM carb for 351's and 429's.<br><br>A vacuum gauge connected to a constant manifold vacuum source will tell you<br>if the airflow of the carb is too restrictive. At the end of a high speed<br>WOT run, if reads more than an 1.0" to 1.5", the carb is restrictive. 1.0"<br>
is good for a high performance street application and 0.7" for more race<br>oriented engines.<br><br>I'm not familiar with that particular carb but it possible that the carb is<br>emissions calibrated and is simply leaning out. If it's a 4160, you'll want<br>
to convert it to replaceable jets on the secondary side and see if richening<br>the mixture fixes the problem.<br><br>Dan Jones<br></div><div class="gmail_extra"><br><br><div class="gmail_quote">On Sun, Dec 8, 2013 at 2:35 PM, Asa Jay Laughton <span dir="ltr"><<a href="mailto:asajay@asajay.com" target="_blank">asajay@asajay.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><u></u>
<div bgcolor="#ffffff" text="#000000">
Hi all,<br>
<br>
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.<br>
<br>
I speculate at 130 MPH, I'm using up all the carb, or all the fuel
pump. One, the other, or both.<br>
<br>
The Carb is a Ford stamped Holley list with these numbers:<br>
<pre>D8PE-9510-KA
LIST 8414
3113
</pre>
This link shows my email back in 1999 with info from Holley that I
obtained.<br>
<a href="http://poca.com/detomaso/1999-09/329.html" target="_blank">http://poca.com/detomaso/1999-09/329.html</a><br>
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.<br>
<br>
What to do.<br>
As always, money is a bit of an issue. I'd like to install EFI but
that's really expensive.<br>
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?<br>
<br>
Does anyone have one they'd be willing to part with?<br>
Should I send mine into someone like Chuck Nuytten and have them do
their magic on it, replacing metering blocks and other mods?<br>
Should I just buy a new one?<br>
<br>
The engine is a 351C bored .030 over, stock stroke.<br>
Heads are <a>DOAE</a>, <a>quench</a> chamber.<br>
Cam is a Crane hydraulic roller with these specs<br>
<img src="cid:part1.09010403.08010708@asajay.com" alt=""><br>
Intake is an FPP 4145<br>
Stock ZF transmission<br>
<br>
I've got some time so I'm looking for some informed/experienced
opinions on what carb would be best.<br>
<br>
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. :)<br>
<br>
Thanks,<br>
Asa Jay<span class="HOEnZb"><font color="#888888"><br>
<br>
<br>
<pre cols="72">--
Asa Jay Laughton, MSgt, USAFR, Retired
& Shelley Marie
Spokane, WA
******************************
<a href="http://www.racingagainstautism.com" target="_blank">http://www.racingagainstautism.com</a>
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<a href="http://facebook.com/racingagainstautism" target="_blank">http://facebook.com/racingagainstautism</a></pre>
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