[TPR] More follow up from Chuck Nyutten

Tue Jan 7 09:18:02 PST 2014

My carb is a Holley 0-4778.  I have changed the jets based on dyno runs with an oxygen sensor.  The carb as-built runs very rich. I also changed the power valve based on engine vacuum.  I would caution you on making any seat-of-the-pants mixture adjustments.  Just have a bung put in at least one of your headers and measure it.  A little rich is always better than a little lean, especially at high rpm.

I have had it above 150 MPH many times but always ran out of balls before running out of carb. :)  My car desperately needs a front air dam since above 150 it gets very light in the front.  I have the air dam, just never got around to putting it on.

The 0-4778 is a 700 CFM double-pumper.  Works well around town and also at Silver State.  Its on a Blue Thunder low-profile dual plane manifold on 4V closed-chamber iron heads.

I agree with Chuck, I would not put a vacuum-secondary carb on my Pantera.

Grumpy

________________________________
 From: Mad Dog Antenucci <teampantera at yahoo.com>
To: Asa Jay Laughton <asajay at asajay.com>; "tpr at teampanteraracing.com" <tpr at teampanteraracing.com> 
Sent: Tuesday, January 7, 2014 7:31 AM
Subject: Re: [TPR] More follow up from Chuck Nyutten

Bud can do 130?
At Silver State? ;-)

Look I can do 185 at sealevel and Bud is somewhere south of sealevel! HAHA
Here's the guys to ask....what is JB running for a carburation...he has had several runs between 130-135 AVERAGE which meant he was hitting 150-160 in straights....

Note to Grumpy:  Chime in here with your wisdom ;-)

On Monday, January 6, 2014 10:05 PM, Asa Jay Laughton <asajay at asajay.com> wrote:

Hi gang,

As I continue my edumacation bout cars and stuff.... I wrote Chuck
    again asking about the option of a vacuum secondary carb instead of
    a double-pumper as he originally recommended.  He was candid in his
    response and I take it with the same grain of salt I try most things
    with.  You can read the trail below.

I also talked with our friend Bud Hower, who sent photos and specs
    of his carb.  His Holley is nearly identical to mine, though it may
    not be an "emissions" model, and he gets 130 top end without a
    problem and maybe more.  That may simply mean mine being an
    emissions carb might be channeled and jet differently... for fuel
    economy and not top end.

Note, I'm not spending any more yet, I'm still investigating.
Asa Jay

-------- Original Message -------- 
Date: Mon, 6 Jan 2014 14:45:10 -0600 
From: <form at chucknuytten.com> 
To: 'Asa Jay Laughton' <asajay at asajay.com> 

If you are going to buy a new carburetor, I would not recommend a vacuum secondary carburetor. I use double pumper carburetors on many vehicles that claim they use them on performance street vehicles. I stay with my original recommendation of a 750-2003 carburetor $833.00. 
Vacuum carburetors tend to drop back on performance on the top end and that is exactly the condition you are describing. A vacuum carburetor is a good choice if you only want fuel economy but you are not going to be happy with that carburetor when you want to go racing. 

From:Asa Jay Laughton [mailto:asajay at asajay.com] 
Sent: Friday, December 27, 2013 1:33 PM
To: form at chucknuytten.com
Subject: Re: Friend or Fellow Racer

Thank you for the recommendation.  Based on the fact I don't race the car all the time and in fact drive it more as an around-town car until open road race season, I would think a vacuum secondary would be better for fuel economy.  Presently I get nearly 22 MPG on the highway, which is nice; when racing, it doesn't really matter as long as enough fuel is being metered to the engine.  However, during the SSCC this year I felt the carb was leaning out and perhaps even starving the engine at high rpm, which is why I'm investigating a new carb.

Do you work with vacuum secondary carbs and what is your opinion
        of them?
Thank you,
Asa Jay

Asa Jay Laughton, MSgt, USAFR, Retired
& Shelley Marie
Spokane, WA
******************************     
http://www.racingagainstautism.com
http://www.teampanteraracing.com
http://facebook.com/racingagainstautism

On 12/9/2013 8:51 AM, form at chucknuytten.com wrote: 
If you want performance, I have a  750-2003 double pump carburetor, four corner idle which would work very well for your situation. $833.00 I looked up the carburetor you presently are running and according to the Holley info I would not recommend putting any more money into that core.  Your present carburetor is an ok core for general use but not the best core for performance.

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