Brad, I believe the thermpquad (made by Carter) has secondary operation just
like the Carter AVS. If that is correct, its somewhere between a vacuum
secondary and a mechanical secondary. You are right, that top flapper thingy
requires engine suction to open. However the butterflies themselves open with
mechanical activation, so technically, its not vacuum secondary (all the above
is assuming the operation is similar to the AVS, which I believe it is). Even
my Quadrojunk in my LeBaron has similar operation (they must have coped it from
Carter). I like this type of carb because you can adjust the linkage till you
are absolutely certain that all 4 "doors" are open letting air fill up all
oversize 8 cylinders!
For the gentleman trying to figure out if his secondaries open or not:
disconnect the choke linkage (or warm up the engine till the choke is open) and
with the engine off, have someone to push the throttle wide open. Open the
flapper valve with your finger and with a flush light, look down the
carburator. The secondaries should be wide open. If not, adjust the linkage
till they are open.
D^2, 2x68s, both secodaries open ALL the way!
Quoting Brad Hogg <roadhogg@xxxxxxx>:
> The Thermoquad IS a vacuum secondary. Meaning that the top flap thing
> stays
> closed until there is sufficient atmospheric pressure differential on
> the
> top and bottom side of it to open it up. This is supposed to decrese
> the
> bog effect of opening the secondaries at low rpm. There is another
> vacuum
> conponent in that the vacuum pot on the right side of the carb will hold
> the
> secondaries closed if there is very low vacuum in the intake (meaning
> there
> is more open throttle and there is rpm to soak it up)
>
> Not a very good explanation but it might help.
>
> BTW, some Thermoquads run great. I have three that do so they're not
> all
> bad.
>
> ----- Original Message -----
> From: "James" <nyb@xxxxxxx>
> To: <mailing-list@xxxxxxxxxxxxxxxx>
> Sent: Sunday, May 04, 2003 2:12 AM
> Subject: Re: IML: Pop goes the carburettor
>
>
> 76 is indeed a Thermocrap. I'm pretty sure it's a vacuum secondary
> carb, but I have seen them open before while in park. Whether they are
> supposed to or not, I don't know.
>
> Brian Collinsworth wrote:
>
>
>
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