[DeTomaso] Vacuum Advance - ported or full vacuum source

[Will Kooiman]

Incorrect.

There were some variations with vacuum retard in the smog years, but most
distributors including modern versions such as a Mallory have 1 port.

It works the same whether it is ported or manifold.  The vacuum is the
same.  The only difference is when you get vacuum.  With ported, you get
zero at idle.  Once you go "off-idle", it exposes the ported hole, so you
get full vacuum.

On 8/27/12 10:10 AM, "Stephen Nelson" <steve at snclocks.com> wrote:

>Unless I am way out of line, wouldn't connecting to the carb port require
>a
>vacuum advance, and going to a full vacuum source require a vacuum retard
>on
>the distributor?
>
>Stephen Nelson
> 
>-----Original Message-----
>From: detomaso-bounces at realbig.com [mailto:detomaso-bounces at realbig.com]
>On
>Behalf Of gow2 at rc-tech.net
>Sent: Monday, August 27, 2012 8:00 AM
>To: dennis617 at aol.com
>Cc: detomaso at realbig.com
>Subject: Re: [DeTomaso] Vacuum Advance - ported or full vacuum source
>
>It can effect your base timing which effects where you end up.
>
>
>
>
>> But unless I don't understand something, that shouldn't matter since
>>under
>> open throttle the vacuum advance drops out of the equation anyway.
>>
>>
>>
>> -----Original Message-----
>> From: gow2 <gow2 at rc-tech.net>
>> To: dennis617 <dennis617 at aol.com>
>> Cc: detomaso <detomaso at realbig.com>
>> Sent: Mon, Aug 27, 2012 10:47 am
>> Subject: Re: [DeTomaso] Vacuum Advance - ported or full vacuum source
>>
>>
>> Simple answer.
>>
>> ith ported you have no vacuum at idle. Manifold you have vacuum at idle.
>> You gain the ability to advance your timing at idle with Manifold. This
>> ives you better throttle response and can help the engine run cooler.
>> Switching from ported to manifold you might end up with more total
>>timing
>> hen you had which means you might need to reduce total timing.
>> Gary
>>
>>
>>>
>>  Does anyone have an opinion on which source I should use for my vacuum
>>  advance on my Mallory Unilite distributor, full vacuum directly from
>>the
>>  intake manifold or ported vacuum from the Holley 650 double pumper?  I
>>  have a mostly stock engine with an Edlebrock Performer intake manifold.
>> I
>>  have recieved conflicting information from Holley and Mallory, Holley
>>  claims that I should use the ported vacuum at the carb and Mallory
>>said I
>>  should use full vacuum from the intake manifold.
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>>
>
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