[DeTomaso] Vacuum Advance - ported or full vacuum source

[Will Kooiman]

The reason they say to hook to ported is because with full vacuum at idle,
it tends to "hunt".

With ported vacuum, the vacuum advance does nothing at idle, so the idle
is more stable.

If you can use full manifold vacuum at idle, that's great.  It runs cooler
and quieter, but if it hunts up and down, switch to ported, and it will
probably stop (hunting).

I would start with full vacuum, and see if you like the way it idles.  If
you don't like it, switch.

Also - with ported vacuum, it sounds better.  It should sound deeper and
have more lope.

On 8/27/12 9:47 AM, "gow2 at rc-tech.net" <gow2 at rc-tech.net> wrote:

>Simple answer.
>
>
>With 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
>gives you better throttle response and can help the engine run cooler.
>
>Switching from ported to manifold you might end up with more total timing
>then 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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