Tony. Thanks for a great description of the quandary. I never could
figure out the pancake breather either. See my reply a few minutes ago
about the problems with start up. During that time, I plugged the
breather just to get the engine to run. I do notice one thing that
confirms your suspicion about lean running. Though the engine seems very
proper otherwise, I do have to pull the choke to absolute max and leave
it on cold start until warm. I think your description of the pressure
inside the engine is probably right. I ordered a plug and will install
to see. Jerry.
Tony Rhodes wrote:
>
> Jerry,
> On the TR4A closed system, there is supposed to be a slight vacuum
> inside the engine at all times. The oil cap has a hole of just the
> right size to allow in the right amount of air.
>
> However, my engine has a long breather pipe on that hole, and
> it APPEARS to have the original PCV system as well. So, it can run well
> with an open system. I do not know what needles the carbs have, however.
>
> It seems to me that if you allow more air into the crankcase than expected
> by the breather system, then you will be allowing more
> air into the intake manifold than expected, which will result in a leaner
> mixture since the breather meets the manifold on the engine side of the carbs.
> Now, you can re-tune the carbs to compensate for the "air leak".
>
> That being said, the Smiths diaphragm unit for the breather has some sort of
> spring in it, so I never understood exactly how it was supposed to work. The
> diaphragm and spring might limit the volume of air (pressure differential)
>that
> the breather will allow....
>
> My advice os to plug the hole back to original spec. But why is it open???
> Too much blow-by on a well used engine?
>
> At least you should install a proper breather tube on the hole to minimize
> oil leakage.
>
> -Tony
> ARhodes@compuserve.com
>
> >Date: Tue, 01 Jun 1999 19:41:33 -0700
> From: Jerry Oliver <slantws@home.com>
> Subject: TR4A Breather plug
>
> Does anyone have an idea what effect not having the breather plug in the
> block on a closed system engine would have? I was under my car (66 TR4A
> nearly finished restoration) this evening, and noticed some oil. The
> hole in the block where the breather would be on an open system car is
> plugged on the closed system. I just have the hole. I haven't driven the
> car yet. The engine was rebuilt several years ago, but the car isn't
> quite finished. I've started the engine periodically and let it warm up,
> and it seems fine. I suppose I should install a plug???
> Jerry Oliver
> Olympia, WA
> 66TR4A 61
> MGA 58
> <
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