[DeTomaso] Intake Reversion

[shawkins777 at comcast.net]

Too much ignition advance can cause these same symptoms. 

Steve 

----- Original Message -----
From: "Kooiman, Will" <will.kooiman at gmail.com> 
To: eb0711 at kolumbus.fi, "forum, Pantera" <detomaso at poca.com> 
Sent: Thursday, May 2, 2013 7:04:19 AM 
Subject: Re: [DeTomaso] Intake Reversion 

Surging and hesitation sounds like it is going lean. 

Reversion sounds like a stretch. It could be, I guess, but I wouldn't 
immediately jump to that. 

Low vacuum sounds like inadequate timing advance. 

Read Carburetor Tuning the Scientific Way by Bob the Oil Guy. You should 
be able to find it on google. Before you start replacing parts, make sure 
everything is tuned properly. 
-- 
Will 





On 5/2/13 2:59 AM, "eb0711 at kolumbus.fi" <eb0711 at kolumbus.fi> wrote: 

>It could also be transition circuit of the carb going lean before main 
>boosters kick in. Not much you can do without changeable pills for air 
>bleeds and fuel restrictors (which are possible to make by yourself as 
>well). Good wideband lamda would be your friend, but trying someone 
>else's carby could help you troubleshoot. 
> 
>5/2/2013 8:50 AM, JDeRyke at aol.com kirjoitti: 
>> Reversion is normally found with very strong pulsations from IR-mounted 
>> carbs like quadruple Webers, not Holley 4bbls. It causes a visible 
>>cloud of air 
>> & fuel to appear 6" or so above the carb throats at a critical rpm. 
>>Exhaust 
>> reversion is harder to diagnose but is normally a low rpm quirk. The 
>> port-restrictors you speak of can be used in both intake and exhaust, 
>>but the 
>> effect of intake stuffers is usually to sharpen up the midrange and 
>>utterly 
>> torpedo the top end. Exhaust stuffers are less noticable and work best 
>>at higher 
>> rpms. Neither will likely fix the engine problems you mention. Simply 
>>going 
>> lean might do what you describe. What kind of "750 Holley" is this- a 
>> vac-sec or a DP? You may need a tuner-Holley for that beast; an 
>>out-of-the-box 
>> carb isn't likely to work very well unless you get luckier than I ever 
>>did. 
>> It's also very hard to separate ignition and fuel problems 'cause they 
>>give 
>> identical symptoms. 
>> As a pure guess, I'll go with JT on this: some sort of carb problem- 
>> possibly a blown or wrong range power valve. I'd try another Holley and 
>>maybe 
>> different plug wires, too. Good luck- J Deryke 
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