Good idea, and it had crossed my mind but I was not sure how to pull it off. I
also have the pleasure of owning two different manifolds for the DGV, a Cannon
and a Pierce. Both of these have a machined flat spot just below the carb
mounting flange, before the runners spread out, where "something" could be
added. There is lots of room to add a PCV valve, resulting in a good vacuum
port. I would expect that the hole should approximate the one on the ZS so I'll
look for a PCV of this size.
If I go this manifold modification route, I'll try it for a while, and if it
does not work out, then I'll fall back to the catch can method.
BTW, I can't make out the details in the photo of the Dellorto but understand
what you mean. ANd I'll take the bet on removing the vent hose off the valve
cover on a 1500 Spitfire engine. You will get oil out the dip stick!
VIc Whitmore
Trevor Boicey wrote:
>
> Vic Whitmore wrote:
> > The whole issue centres around the use of the Weber DGV (and as Joe pointed
>out
> > the DCOE). It does not have the same vacuum port as in the standard carb,
>the
> > ZS. It has only one vacuum attachment and that is used for the distributor.
>
> Agreed, you cannot use ported vacuum for this job for
> the reasons you talk about. However, there are other sources of
> vacuum to be had.
>
> Have you checked the manifold?
>
> I have done this exact job on two DCOE webers, and both
> had extra ports on the manifold available to be used. It
> seems these manifolds are sort of "generic" so they
> come with blocked off ports that you can use in
> certain applications and ignore in others.
>
> I had a Dellorto DCOE clone for A-series Midgets, here's a picture:
>
> http://www.brit.ca/~tboicey/mgparts/pics/midget_dellorto_carb_1.jpg
>
> ...there is a capped port on the manifold, visible on the left
> side of the picture. It's a simple matter of unscrewing
> the blanking plate, and screwing in a vacuum tap from your
> local PEP boys.
>
> I don't have pictures, but I did a similar job on a DCOE
> for a friends MGB. That manifold already had a vacuum port
> actually, it was capped off with a rubber seal that just
> needed to be cut open and removed.
>
> The UK spec dual-SU manifold also has a plugged port:
>
> http://www.brit.ca/~tboicey/midget/pics/midget_overdrive_day_five_5.jpg
>
> In these applications, I would usually plumb in a $5 PCV
> valve instead of a restrictor. It gives an extra safety
> margin, because the manifold vacuum can get so high at cruise
> and idle, and this way it will only flow air when the
> crankcase pressure is above ambient air pressure.
>
> > Just try removing the hose from the valve cover and run like that for
> > a while. I will guarantee that you will get the same problem, oil pumping
>out
> > the dip stick.
>
> I'll happily take that bet. With the crank open through
> the valve cover, no pressure will build to pop out the
> dipstick.
>
> --
> Trevor Boicey, P. Eng.
> Ottawa, Canada, tboicey@brit.ca
> ICQ #17432933 http://www.brit.ca/~tboicey/
> "What am I, Julie from the Love Boat?" - Julie, from the Love Boat
--
Vic Whitmore
76 Spitfire
Thornhill, Ontario
http://www.vicwhit.com
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