Smoke from engine breather pipe

Hi everyone, I’m new here, but need some advise.
I’m currently rebuilding a series 2 FHC 4.2. Engine has been rebuilt around 8 months ago but it’s taken until now to actually get to a point where I can turn it over. I’ve static set the timing to 10 BTDC and set the carbs to the starting point for tuning. Engine stated surprising easy running a little fast so carbs will need some tweaking, but I’ve got my concerns, and I’m hoping someone has had this before.

First of all I’m getting lots of smoke from the breather pipe that goes from the head to the air intake. Beginning as soon as it fires and gradually gets worse as the engine warms up to something like a boiling kettle.

Second the oil pressure gauge climbs and climbs right off the scale until the needle disappeared.

Thirdly it warms up fast and I’m Sure I might be getting a bit of blue smoke from the exhuast but hard to tell because by this time the Smokey breather has filled the garage with unbearable eye stinging smoke.

Plus seems a bit tappety top end.

So I’m angry and confused that it’s a rebuilt engine and I expected it to be lovely. I’m Worried something major is wrong and it needs taking apart again, after I’ve put so many hours into building the engine bay.
Before I go and rip the engine builder a new A hole, I thought I’d ask if anyone has had this before or if I’ve missed something?

What you’re describing is blow-by. That is, combustion gasses are getting past the rings into the crankcase. Since this is a fresh rebuild, I might expect your rings aren’t yet bedded in - something that may require some hard acceleration on the road.

A compression test will confirm.

Also possible since the engine’s been sitting there’s condensation in the crankcase contributing to the smoke. An oil change wouldn’t hurt.

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Oil pressure keeps climbing - possible sign of cylinder compression going past rings in to the oil sump - engine sitting for 8 months may have piston rings stuck so need re-seated in piston grooves - possibly pouring in a little ATF (automatic transmission fluid) in each cylinder, let sit for a while - take a compression test (with all spark plugs removed) and verify that the rings seemed to have sealed - for comparison, take a compression test before putting in the ATF - Tex.

Also, if your car has had a Series III Xj6 fuel pump fitted as part of the rebuild, as mine have, the pump pressure can exceed the full scale on the OP gauge - especially at start up for a 60psi gauge.

?? Blow by would not increase oil pressure at all. More likely the bypass valve in the filter adapter is hanging up.

I would not add extra oil of any kind into the cylinders until the rings have seated, which is not going to occur until you get it on the road and apply some moderate load to the engine.

Don’t fret yet. Fresh engines can be smoky, smelly beasts until they get a few miles under it’s belt(s).

Yeah. I would definitely fiddle with the oil pressure relief valve. Procedure in the manual.

(And second the advice not to fret. I’ve got a somewhat smoky rebuilt 3.4 litre engine I’m looking forward to put under some load once I can get the car back on the road.)

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E Types typically show very high oil pressure on start up. It’s not unusual for the needle to go off scale until the oil warms up ( which can take 15 mins or more at idle), particularly if you are using 20-50 oil.

If you have new valve components you should run the engine for 20 mins at 2000 rpm to break those in. Best to insure your fan is working and have an aux. fan in front of the rad.

For break-in use a light cheap oil - never use synthetic.

Sorry about the blow by - it may indicate a serious problem. Of the 25 plus engines I’ve rebuilt over the years none have had unusual amounts of blow by. I’d try a compression test, or better a leak down test. Harbor Freight sell an inexpensive leak down tester. You won’t get the factory results without the rings being broken in but it may show something. As Nick says, when you get it on the road give it full throttle from 1500 rpm to 3500, 5 - 10 times.

Good luck.

Make sure you don’t have an air lock in the cooling system remove your thermostat if your concerned

A lot of info. And a lot of well meaning advice above; some good some less so.

Some of the things you describe are normal. Some are not.

Working out what’s the actual problem virtually, is nigh on impossible.

I’ve been building XK engines for 15 years and my advice is simple.

There’s a problem. You don’t (shouldn’t) know how to fix it. Take it back to the engine builders and get them to address your concerns.


Thanks for your comments guys. Much appreciated. Some good info. I’m really hoping it doesn’t have to come apart again.

Andy, both your water temp gauge and oil pressure gauge source power through a resistor that reduces the voltage. If the resistor is bad, one or both gauges will read high. The resistor is $20 from Moss. Mine was bad and my water temp did the same thing.
My freshly rebuilt motor also smokes thru the breather. I’m fairly sure the rings need to seat. Fix your gauges and drive it a few hundred miles.

I may have missed this but, was the block bored? if not, did they use chrome rings?

It’s not a resistor, but a voltage regulator device that uses a bimetallic strip surrounded by a heating coil. It tries to maintain an average of 10 V. Pardon me for being picky but I am a retired electrical engineer.

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…and while we’re being picky @Johnnycaps statement about the oil pressure gauge using this regulated power source is also incorrect. The 10v regulated power source is only shared by the water temperature gauge and the fuel gauge. The oil pressure gauge uses full battery voltage.