Hello,
The stock emissions system is really bad because if you have too
much blowby, it will back up into the carbon canister and ruin it.
Fortunately my engine is in good shape and does not have
much blowby, so I did not have this problem when the stock carb
was installed.
My HS2 manifold has a mushroom-shaped valve on it that is essentially
a PCV valve. I have connected this directly to the valve cover,
like it is meant to. Thus my crankcase ventilation system works OK.
(I used a ported vacuum connection on one of the carbs
to purge the carbon canister. This vacuum connection does
not work at idle, only at part-throttle, so hooking it
to the canister (instead of capping it off) has no
effect on the engine operation. And, there is no way
blowby can get into the canister.)
MK II cars took the line from the valve cover and fed it to the
air filter, so that the blowby would get sucked back into the engine.
But this approach does not provide "positive" ventilation.
On a good PCV system, the carb is supposed to suck more than
the amount of blowby. Thus, a slight vacuum is created in the crankcase,
and filtered fresh air is let in to actually ventilate the crankcase.
The Spitfire's system doesn't really do this. It doesn't really
"ventilate" the crankcase at all, it just keeps the blowby from stinking up
the atmosphere.
In your case, you might consider doing this: Drill a hole in the manifold,
thread it, and install a 1/2" or so hose nipple. Hopefully
the manifold already has a place for this. Connect a short hose
to this and to one end of a plain-vanilla PCV valve. The other end of
the valve will have a hose that goes to the valve cover. You
should find a valve meant for a small 4-cylinder engine (e.g. Datsun, etc.).
Note that theoretically, sending blowby to the carb or intake manifold
should not upset the mixture, since the stuff is already a mixture
of air and gas and inert combustion by-products.
On my car, if I disconnect the hose from the valve cover, the manifold starts
sucking air instead of blowby, and the engine starts running bad.
I tried an experiment this morning: I connected a longer
rubber hose to the valve cover and I blew into it. I listened
for hissing to see where the crankcase was actually ventilated to.
The main location was a small hole drilled in the underside of the
fuel pump! It also leaked a little around the valve cover hold-down
nuts and the base of the distributor. I guess this explains why
it is always sort of oily and dirty under my distributor...
Good Luck,
Doug Braun
'72 Spit
At 11:49 AM 8/2/00 +0000, you wrote:
>Did you change the header? I went with a Pacesetter.
>
>I have a Monza exhaust and a weber down draft. I recently put in a new valve
>cover gasket
>and immediately had an excess oil pressure problem and oil blown out the
>dipstick. I
>guess the old gasket was leaking enough to let out the excess pressure. I
>have the
>emission hose to the carbon cannister dangling now and it seems to have solved
>the
>pressure problem. I don't like this as a solution.
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