PDA

View Full Version : Cranckase Overpressure and Excessive Valvetrain Wear Woes



ruuskado
06-23-2014, 03:10 PM
So, I have a 1962 Series IIa Station Wagon with a 2.25L petrol, 3-bearing engine. The block # is 25228710G. I have a longstanding issue and thought perhaps that someone here might have some insight that could help me out. I bought my Landrover back I 1996 or so and used it for quite sometime before I had to replace the cylinder head. The original was designed for leaded gas, so eventually it wore out. I replaced the head with a unit re-built by Turner Engineering in England modified for use with unleaded gas. I did this in 1998 or so.


In 2010 I had the engine of the Rover completely rebuilt: ground the crankshaft journals, new journal bearings, cylinders bored 0.040” over, new pistons, rings, shaved the head, new camshaft, replaced all of the lifters, new freeze plugs, etc., etc. At the time a leak-down test indicated that the valves were fine, so we left them as they were.


There are two issues that I have, most likely related, but lets take them one at a time. During the rebuild I discovered that the diaphragm of my PCV valve was kind of shot and I could not find an exact replacement for it, so I thought that I could just use one from some other car, so put on in-line with the PCV hose. On her first long run after the rebuild I went down to NYC. Every once in a while on the highway, she would let out a belch of blue smoke. Now the input to the PCV valve comes out of the oil filler tube and the output feeds into the intake manifold for cylinders 3 & 4. Another thing that I noticed was that my engine was spitting oil out from everywhere, through the oil filler cap, the valve cover gasket, the rear main oil seal, etc. My fuel mileage also went down, before the rebuild I would get 16-17mpg on the highway, now I was lucky to get 10-12. Disappointing really after all that time and effort. She was running a little hot as well, which I took to be from the increased bore volume, so I increased the carburetor main jet by a couple of thousandths. The bore went from a stock 3.562” to 3.602”, which is about 2.25% larger. The head was shaved a little as well, 0.008”-0.010” so the compression ratio was increased too.


I finally was able to keep the oil from spewing from everywhere by finding a New Old Stock PCV valve. This has reduced the pressure I the crankcase, but it still burns a lot of oil by passing it through the PCV valve and burning it up in cylinders 3 & 4, as evidenced by occasional clouds of blue smoke and some pretty fascinating ash deposits on the spark plugs of those two cylinders. So, now the symptoms are a bit different, but that particular problem is still there.


Now, issue #2: I had to have the cylinder head rebuilt in 2012 as the valve train had completely wore out, the garage, which specializes in Landrovers, said that they had never seen valve guides so worn out before. After that the valves are OK, but the initial problem still existed a described above. A compression test was done at the time both dry & wet and the results were dry: 145, 140, 135, 145 wet: 155, 155, 145, 150, so not too bad. Now, here we are in 2014 and the valve guides are apparently worn out again. This should not be happening, the engine is not driven hard, or extremely long distances, so I would have expected 10 years, or more, before this type of wear. The tappets were not worn the last time. I will be tearing into it in 2-3 days and will see what I have this time around.


We have eliminated the cam timing being off as a source of this. One hypothesis is that one, ore more, of the ring sets were installed upside-down, thereby pressurizing the crankcase more than it should be but more that that I have run out of ideas. I guess that it is possible that the oil passages to the head are blocked, but then I would expect that the tappets and lifters would wear out too. Anyone out there have any advice?

Thanks,

Doug

SafeAirOne
06-23-2014, 03:53 PM
Is a sufficient amount of oil reaching the head?

What oil pressure are you seeing?

o2batsea
06-23-2014, 04:12 PM
To my feeble recollection there was no PCV system other than a vented oil cap on that vintage truck. In those halcyon days, crankcase vapors went straight to the atmosphere. So with that in mind there shouldn't be any build up of internal pressure. The thing that will wear the guides is lack of oil. Are you sure the oil feed tube on the back of the head is clear and free flowing? As Mark alludes, you don't mention anything about the oil pump being redone at any time. Do you have an oil pressure gauge on the truck at all?

ruuskado
06-23-2014, 10:41 PM
I re-built the oil pump when I re-built the engine in 2010. I cleaned it thoroughly and put in new idler and drive gears, seals and washers. The relief sleeve, (piston), was jammed in the bore and I fixed that as well.

Tonight I get 35psi idling and 50-55psi while driving around the city.

I tried using no PCV valve at all and just vented the tube from the oil filer tube directly into a Qt. gear oil container, but I STILL had too high of a pressure in the crankcase.

o2batsea
06-24-2014, 09:49 AM
How can that be? With no PVC valve, the crank case will vent straight to mother nature, so there is absolutely no possible way it can build any pressure. What are you using to measure "crankcase pressure"? This is a Series 2A petrol engine, yes?

ruuskado
06-24-2014, 01:20 PM
My thoughts exactly, now you can see why I am so puzzled. The evidence of crankcase pressure was oil being forced out of the rear main engine seal, up out of the oil filler tube cap and beneath the valve cover.