MG
The Classic Marque

After 21 years of ownership, it's time to replace my YT's bottom seal on the windscreen. Dunno how old it is but the seal against the cowl is terrible and being caught in heavy rain means wet legs and instruments.
Can the brains trust tell me what's involved to replace the rubber seal between my folding windscreen and the scuttle cowling? Do I need to dismantle the windscreen frame to do this...

There is quite a bit on line on the subject. This from some smarty-pants AI thingy:

PCV valve size is crucial for matching engine displacement. Proper sizing ensures optimal airflow and effective crankcase ventilation. Here are some general guidelines:
• Engine Displacement: The size of the PCV valve should correspond to the engine's displacement. Larger engines typically require l...

Just to add to this--
When you get it apart, or more when you're sticking it back together, check the bush inside 3rd gear for wear, If it's worn ,although while 3rd is selected and the gear and shaft are rotating at the same speed,if there is too much clearance there the gear get's loaded over to one side and causes the gear to run out of true with the shaft and syncro assembly--Can be the cau...

Although a similar age to Marley, he became known first and laid the ground for Marley. RIP.

Paul W, do you have any idea of size for the 1800 cc B series engine please? What does the 'size' refer to for a PCV? Thanks

Those valves work well, but the size needs to be matched to the engine size.
A wrong sized valve will result in oil being drawn into the manifold.

Paul, That’s exactly what was happening. As I increased the revs the strobe was showing a retardation, the distributor was moving by the vibration. Once reset and tightened enough it shows an advance when revved as it should. Hope I haven’t wasted your and other contributors time but I have learned a lot from this thanks again Trev.

A modern one should be fine, I'd have thought, and less likely to fail. Yes, should be central so air flow has the same effect on both halves of the engine even though it is pretty small, which is why both carbs have one.

Incidentally does the catch tank have an outlet and where does it go? A comparatively cold surface like that would encourage condensation, like in the long oil filler ...

Thanks for your feedback Paul. Using a PCV is the conclusion that I was coming to. As pucker MGB PCVs are no longer available at a sensible price I did wonder about using a 'modern' one like this with a suitable tapping/fitting in the brass plug in the centre of the manifold. I understand that it not advisable to use one of the ready tapped ones either side of the centre.

No through-flow ventilation hence nothing to take condensation away hence mixing with oil and the sludge.

If the carbs don't have PVC ports you really ought to fit a PCV valve to the inlet manifold somehow. The factory PCV valve used adapter 12H1405 with a sealing ring, you may be able to tap the manifold for that. Alternatively you could go back to the system used before PCV which is a...