Holley Vac sec question

[Ext User(james)]

OK so i'm trying out a 750vac sec holley on my 308 and i don't believe
the secondaries are opening. I realise the carb may be too big for my
engine, would that prevent the secs from opening or will they open
regardless of if needed or not? It has a plain coloured spring in it,
so it should be opening by 3000rpm max. I've had it up to 5000 and
they don't seemto open. I have put a paper clip on the canister rod,
as per the way holley say to do and it didn't move, the linkages
arn't stopping the secs opening though when the throttle is open so
that's not the problem. I've checked the diaphram and the little crok
gasket is there between the canister and main body.
So should or shouldn't they be opening or is something wrong ?

[Ext User(chris)]

they will only open under load as all mine do you can put a bolt in the
linkage to make it open manually
"james" <kaufman_j@hotmail.com> wrote in message
news:84nk32dntcj36bbg2ttv3gjpub1kocenk4@4ax.com...
> OK so i'm trying out a 750vac sec holley on my 308 and i don't believe
> the secondaries are opening. I realise the carb may be too big for my
> engine, would that prevent the secs from opening or will they open
> regardless of if needed or not? It has a plain coloured spring in it,
> so it should be opening by 3000rpm max. I've had it up to 5000 and
> they don't seemto open. I have put a paper clip on the canister rod,
> as per the way holley say to do and it didn't move, the linkages
> arn't stopping the secs opening though when the throttle is open so
> that's not the problem. I've checked the diaphram and the little crok
> gasket is there between the canister and main body.
> So should or shouldn't they be opening or is something wrong ?

[Ext User(a9x5l)]

On Mon, 10 Apr 2006 13:31:23 +0000, james wrote:

> OK so i'm trying out a 750vac sec holley on my 308 and i don't believe
> the secondaries are opening. I realise the carb may be too big for my
> engine, would that prevent the secs from opening or will they open
> regardless of if needed or not? It has a plain coloured spring in it,
> so it should be opening by 3000rpm max. I've had it up to 5000 and
> they don't seemto open. I have put a paper clip on the canister rod,
> as per the way holley say to do and it didn't move, the linkages
> arn't stopping the secs opening though when the throttle is open so
> that's not the problem. I've checked the diaphram and the little crok
> gasket is there between the canister and main body.
> So should or shouldn't they be opening or is something wrong ?

I've used a 780 vac sec on a 283 Chev and I can assure you that the
secondaries did open. The carby was set up for a 400 small block and IIRC
had the lightest spring(can't remember colour).

--
a9x5l

[Ext User(james)]

On Tue, 11 Apr 2006 17:55:35 +1000, a9x5l <a9x5l@hotmail.com> wrote:

>On Mon, 10 Apr 2006 13:31:23 +0000, james wrote:
>
>> OK so i'm trying out a 750vac sec holley on my 308 and i don't believe
>> the secondaries are opening. I realise the carb may be too big for my
>> engine, would that prevent the secs from opening or will they open
>> regardless of if needed or not? It has a plain coloured spring in it,
>> so it should be opening by 3000rpm max. I've had it up to 5000 and
>> they don't seemto open. I have put a paper clip on the canister rod,
>> as per the way holley say to do and it didn't move, the linkages
>> arn't stopping the secs opening though when the throttle is open so
>> that's not the problem. I've checked the diaphram and the little crok
>> gasket is there between the canister and main body.
>> So should or shouldn't they be opening or is something wrong ?
>
>I've used a 780 vac sec on a 283 Chev and I can assure you that the
>secondaries did open. The carby was set up for a 400 small block and IIRC
>had the lightest spring(can't remember colour).


Hmm well i've just tried it with a weaker spring (short yellow) and
also with the ball removed from the vacuum passage in the canister.
I've also checked that the passages are clear that are in the main
body (the ones that end up at the vacuum canister)
They atill do not appear to be opening.

[Ext User(Magic Mushroom Farmer)]

My thoughts exactly...force them open is the best solution,however with
the idiotic gear ratio's to power curve on these types of cars in stock
and even boganised modified configurations it will possibly still just
billow and hollow and go not move much when they are open,gear it like
a truck,it will go like a rocket ship almost,and lay rubber when they
are open if you are lucky,power curve on 8's is not really suited to
high revs unless,engine is well ballanced and well flowed,could go on
for hours about this,you got heaps of bottom end power(its why they are
geared that way),best stick to it or spend a small fortune,top end is
not really gonna help unless you modify the power curve and make it rev.

[Ext User(a9x5l)]

On Tue, 11 Apr 2006 09:43:18 +0000, james wrote:

> On Tue, 11 Apr 2006 17:55:35 +1000, a9x5l <a9x5l@hotmail.com> wrote:
>
>>On Mon, 10 Apr 2006 13:31:23 +0000, james wrote:
>>
>>> OK so i'm trying out a 750vac sec holley on my 308 and i don't believe
>>> the secondaries are opening. I realise the carb may be too big for my
>>> engine, would that prevent the secs from opening or will they open
>>> regardless of if needed or not? It has a plain coloured spring in it,
>>> so it should be opening by 3000rpm max. I've had it up to 5000 and
>>> they don't seemto open. I have put a paper clip on the canister rod,
>>> as per the way holley say to do and it didn't move, the linkages
>>> arn't stopping the secs opening though when the throttle is open so
>>> that's not the problem. I've checked the diaphram and the little crok
>>> gasket is there between the canister and main body.
>>> So should or shouldn't they be opening or is something wrong ?
>>
>>I've used a 780 vac sec on a 283 Chev and I can assure you that the
>>secondaries did open. The carby was set up for a 400 small block and IIRC
>>had the lightest spring(can't remember colour).
>
>
> Hmm well i've just tried it with a weaker spring (short yellow) and
> also with the ball removed from the vacuum passage in the canister.
> I've also checked that the passages are clear that are in the main
> body (the ones that end up at the vacuum canister)
> They atill do not appear to be opening.

Is it second hand? If so, can you verify that it hasn't been "tweaked"
previously? Unfortunately when buying second hand Holley carbs it's all to
common to get one where the owner thought he knew better than the
manufacturer about how to make it operate properly therefore buying S/H be
a bit hit and miss.

If you take the unit off and suck on the vacuum port, does the pushrod
stay in or drop back? I only ask because often the diaphragm can appear to
be okay but leak around the outer edge were it seats on the canister. It's
been a long time since I've messed with vac sec Holleys but I seem to
recall(when the seating area of the diaphragm was getting a bit long in
the tooth) using a light dab of gasket goo on the mating surfaces just to
ensure that it sealed.

--
a9x5l