Z145 vacuum line causes problems

CitrusGrower · Dec 1, 2017

I put new pistons and valves in my Z145 engine in a Massey Ferguson 30B tractor (similar to a 135). It runs well to do work, but I have to set the idle up to 1200 to keep it from stalling.

There is fair sized piece of rubber tubing (3/8") that connects just upstream of the carburetor and runs to the valve cover vent and the intake manifold. It seems like a huge vacuum leak to me so I clamped off the line going to the intake manifold and the engine runs much better.

What's the purpose of this line? And am I missing a part like a check valve or small orifice? All I've got is tubing and a metal T connecting the 3 pieces of tubing together.

I'd swear this is the way it was originally, but that big connection to the intake manifold makes no sense to me.

ptfarmer · Dec 2, 2017

The parts book shows it, but you don't need it, cap off the vacuum from the intake manifold, and cap off where it hooks to the valve cover. All the older Z145's just had a big tube that bolts to the valve cover on the left hand side, and it runs down the front of the engine. Your valve cover should have that tube on the left hand side of the valve cover.

Gambles · Dec 2, 2017

I'm not familiar with the Massey 30B tractor, but from the OP's description, it sounds like this hose removes moisture from the valve covers and reburns the blowby that gets past the rings. You said that this hose isn't needed, but wouldn't you want it? I realize that 50 years ago there was no emission parts on a car, but some things, like the pcv systems are actually beneficial. Am I missing something?

Phil Tibbetts · Dec 2, 2017

If you want to keep it try putting some sort of restriction in the line to cut down on the flow rate. Unless the line is original it may have had a restriction or orifice in it originally.

CitrusGrower · Dec 2, 2017

I'm leaning towards taking Gambles advice. It sounds like none of you know or can imagine a reason for a big leak in the intake manifold. But letting the engine burn whatever comes out of the valve cover might be a tiny plus for emissions and sucks moisture out of the engine.

ptfarmer · Dec 2, 2017

That hose where it T's off also runs to the tube between the air cleaner, and the carburetor. With the other tube on the valve cover vented directly to the atmosphere with no kind of filter on it will also allow the engine to suck in dust, and dirt (kind of defeats the purpose of having a air cleaner). The way that it is, it's not the way a true pcv system is setup, its more like a "ooops we need to cobble up some sort of crank case vent just to make a few people happy". It's a poorly executed pcv system.

CitrusGrower · Dec 3, 2017

It is a poor/primitive system, but as you pointed out, it keeps dust out of the engine. I'll settle for that.

ptfarmer · Dec 4, 2017

With the other vent open to the atmosphere without a filter it can possibly suck in dust, and dirt. Re-read my last post carefully. It really needs a pcv valve for it work properly, look at a real pcv system on a car, or truck.

Z145 vacuum line causes problems

CitrusGrower

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ptfarmer

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Gambles

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Phil Tibbetts

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CitrusGrower

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ptfarmer

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CitrusGrower

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ptfarmer

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