Engine and Transmission Tech

I run forged rocker setup on this race engine (not rollers). I have also reduced both the cylinder head oil feed to the rockers from 4.7mm hole to 1.5mm.
Engine has been leakdown tested and all cylinders has 1-1½% blowby, so the rings is sealing well.

Still some oil find it's way up into the rocker cover breathers (is also baffled) at high RPM.
The oil fumes that the catch tank contains (approx ½ litre after one race) is totally dark grey, but engine oil is fine and as new. (oil temp is 85 degrees).

I hope the camshaft splash guard (oil baffle) will prevent oil splash from cam and crank to splash up into the valley and cylinder heads. If oil can run down into the big hole above the camshaft it can also go the other way in form of splash.

Cam lobes should still be lubricated from splash oil from crank and oil from oil baffle sealing dripping.

If you look at an engine from below you will see that the oil will have great difficulties getting back to the sump due to the rotating camshaft lobes and crankshaft counterweights and conrods spinning. Combined with that engine blowby only can enter the breathers via the cam valley holes you have upward moving air at the same time oil tries to go down. Can't be a good coctail :-)

Thats why I now have drilled two 10mm holes from timing chain area into the valley. Maybe the holes are to small ?

Well, I have to try all this out when race season starts, but it is nice to hear some suggestions.



Edited 1 time(s). Last edit at 01/10/2012 04:30AM by perboddum.

Per, are you using a crank scraper ? Drainback holes in the front "china wall", are a good idea. There is ample room behind the rear china wall to run 1+ drain lines into sump area. Do your connecting rods have "squirt holes" at their parting lines, aimed at the camshaft ? Roller cam ? They require much less lube than flat tappet,(no need for squirt holes). Good Luck, roverman.

Thanks for your reply

>>Per, are you using a crank scraper ?
The one that is fitted to the JE sump does not reach very far. I have now extended it some 40mm without interference problem.
I also think part of the problem lies here.


>>Drainback holes in the front "china wall", are a good idea.
>>There is ample room behind the rear china wall to run 1+ drain lines into sump area.
I have to look further into the rear drainback option. Remember my drysump pan is flat so it is difficult to make a drainback.


>>Do your connecting rods have "squirt holes" at their parting lines, aimed at the camshaft ?
No. they are JE steel rods. Don't know manufacturer.


>>Roller cam ? They require much less lube than flat tappet,(no need for squirt holes).
No. Crane 248 cam and oil supply to heads is limited from 4.7mm to 1.5mm.

One time when I had the rocker cover off I noticed that at above 2000 rpm there starts to come many squirts of oil from the camshaft area and up through the cylinder head drainback holes and out on my garage floor. Didn't have the courage to rev it past 2500 rpm, because I would have been shoot all over with oil bullits.

By the way engine has only done some 2000 miles from new.

Per

Per,
You have experienced the breathing problem that these engines suffer from, first hand.
Pressure from the crankcase has nowhere to go except up through the slots at the camshaft and into the valley.
Once the spinning cam picks up a good load of oil it effectively blocks any drain back through the slots.
The pressure from the crankcase picks up this oil and blows it up through these slots.
The way the slots are laid out causes them to scrape some of the oil from the cam and pump it up into the valley as well, making the drain back even worse. On top of all that the oil then gets heavily aerated from all this and turns up in your catch can as a grey looking fluid. If you let that fluid sit long enough it will separate back out into oil and probably some moisture.
My experience says that you need to provide some significant breathing to the crankcase below the valley. Add a proper crank scraper and provide oil drains back from the heads. They hold a significant amount of oil when the engine is running.
Others will disagree, but I would be reluctant to drill the "china wall". These engines have very little meat connecting the two banks together and the two walls constitute a large part of what little there is.
Later this spring I'm going to try out my cam scraper idea. I'll let you know how it works out
Cheers
Fred

Hi Fred

I have the same thoughts as you. That's why I think it was a good idea with a breather at the timing cover combined with two drilled holes through to the front end of the valley. Then you get an extra air route to the crankcase. Just hope that the timing cover don't get filled up, but I think that is most unlikely.

Have not thought of the bottom of the valley as a cam scraber, but I can now see that it proberly will work that way. That is not good....I have seen some big US V8 engines where the valley area is totally closed above the cam, with only 2 drainback holes, front+rear.

About drilling the "china wall", remember the inlet manifold provide some rigidity to the block.

Per

Looking at this as a system, it should be possible without great difficulty to make a few changes which will have it pumping air and suspended oil back towards the pan. Let's start with the idea that two things create positive pressure in the crankcase: blow-by, and aeration in the area of the crankshaft. The valve covers and to a lesser degree the lifter valley become an area of lower relative pressure. Venting the engine from the valve covers only encourages the oil to go upwards. So the first order of business it to provide large diameter equalization lines from the valve covers back to the crankcase, preferably to the pan below the level of the crank scraper and either on the opposite side or provided with a baffle, or both. If this is not possible the front cover would possibly be the next best as it is vented to the pan, provided the lower openings are large enough. This is to let the crankcase pressure pressurize the valve covers but without carrying oil up. Next would be a series of passive flow inducers in the downwards direction, taking the form of modified scraper/deflectors. The idea being that rotation of the cam and crank can be used to create a centrifugal pump which will pump the air and oil downwards. Starting at the top, where you now have your fabricated shield, if you were to do no more than make a sheet which projects into the slots at an angle upwards to the left a bit and more or less completely blocking oil from the cam from being flung to the right through the slot, extending downwards as close to the cam as you can get it without touching, then the rotation of the cam will suck oil through that gap and cause it to be flung downwards. Then a second scraper below and to the right of the cam, angled downwards to the left relative to cam rotation, will peel the oil off the cam and direct it downwards where it will be picked up by the crank windage. If the downward edge of this scraper is matched to the crank and it is bent downwards to the right it too will act to pump the oil downwards like the one above the cam. (With the right angle and placement, the use of a flat scraper/deflecter should be possible) Then a scraper on the opposite side of the pan will help to keep the oil in the pan where it belongs. Finally, a deflector can be used below and to the left of the cam to keep windage away from the cam, however you must determine what your oiling requirements are for the cam lobes and whether this is going too far. In a race engine I would think it would be a help. A second crank scraper part way up the block may be a good idea too, as on hard left hand turns the oil in the pan (if it is a wet sump) will overcome the first scraper.

I've not built this system, but I'm sure you can see how it would work. Once you have equalized the pressures the centrifugal forces would be very effective at making the oil go where you want it if directed properly, bearing in mind the direction of rotation.

Bear in mind too that anything you do with the vent lines which causes an upwards instead of a downward air flow will counteract these devices to some degree. With that in mind, it would be best to vent the engine from the crankcase level if possible, using lines which do not connect to the valve covers. We are trying to get the air to flow downwards. The blowby creates a special problem in this regard. If it can be drawn off directly from the crankcase that would seem the most direct, but if it is drawn off from the pan level it creates a downward flow. On one hand reason dictates that it should be separated as much as possible from the equalization lines, but on the other, if we are using pressure rather than vacuum to remove crankcase gasses we want the valve covers to be at the same pressure as the pan, meaning that pressure from blowby gasses must be transmitted as directly as possible (externally) to the valve covers. Obviously minds will differ on the best way to do this.

Jim



Edited 1 time(s). Last edit at 01/11/2012 11:22AM by BlownMGB-V8.

Hi Jim

I agree with you in theory. In practice I think I will get into space problem with the cam scrapers and how to fasten them.

Also my drysump is a flat cast alu-pan. There is less than 1" from crank weights to bottom of the sumppan.

Anyway your suggestions sounds right and I will look more into what is possible, within the engine space avaible.

Thanks for your suggestions

Per

Jim,

You were awake all night figuring that one out . . . :-) The part that got me hooked is figuring out how some of us can use an efi manifold and vent from the crankcase instead of the valve covers. After reading all about these engines over the last few years, I don't know why anyone wants to vent from the valve covers. (Sorry-Rocker Covers, I'm showing my age).

I think I'm working this out but wonder if I could use a port on the cold-air intake behind the K&N filter to aspirate the rocker covers to the crankcase and then to the EFI intake manifold. The restrictor hole recommended from Rover is awfully small for the 14CUX system.

Using a Buick front cover with a fuel pump plate vent (and appropriate back-flow reducer) I could see how this might work. How would you route the vent from the CC to the the manifold?

Tim

Tim, the small Rover vent orifice is there only to restrict the fresh air that is circulated through the engine, and only for the purpose of allowing good A/F mixture control at idle. (above that it is more or less insignificant) Because this oxygen laden air is eventually ingested it does affect the mixture. At WOT and max blowby manifold vacuum drops to near zero so little or no fresh air is ingested.

If you plumb the large vent line to manifold vacuum in keeping with British practice then you certainly do not want to increase the size of the orifice, as you would lose all control of idle speed and mixture. Then in your large vent line you want to be very certain to include a flame trap of some sort. A canister stuffed with a metal dish scrubber is excellent and does not restrict flow.

Some intakes have a threaded port into one of the runners, or a boss for such a port that can be drilled and tapped. Such a port with 1/2 or 3/4" pipe threads would be ideal.

Jim

After the above modifications, I have been running the engine for 2 years without any oil problems at all. The oil catch tank connected to the rocker covers, dont get filled with oil anymore.

I only have one 15mm vent hose from each rocker cover to the oil catch tank. The catch tank never gets filled with oil any more.

The engine runs to 7200 rpm.
Before the modifications the engine filled the catch tanks very quickly. Now I never emtyes them.

Modifications done to resolve my drainback problem.
--------------------------------------------------------------------------
1: Camshaft splash guard
2. Crankshaft scraper
3. Two 12mm drainback holes behind the camshaft timing Wheel
4. Reduced oil to rockers (1.5mm feed hole)
------------------------------------------------------------------------------------------
That solved my drainback problem

Per

Per, thank you for the follow-up and congratulations for finding a solution!

I had forgotten about this thread, and I'm especially happy to re-read Jim B's last two posts. My engine is worlds away from your racer, but I think Jim's PCV ideas might help me improve it. So that got me surfing through the 300 pages or so of Jim's "340" thread, where I found this killer photo and helpful caption:

Quote:

This PCV system uses the British format with an orifice breather on the opposite corner of the engine. The stainless line was sand packed and formed using a custom fabricated bender. It draws filtered air through the engine via the orifice and then into the blower inlet under vacuum under normal conditions (also assisting in sealing small oil seepages) and vents blowby directly to the inlet under WOT. The inner diameter of the tube is about 9/16". The large canister below the tube is the stock Rover flame trap which prevents crankcase explosion in the event of a backfire and also separates oil vapors and droplets and returns them to the rocker box.

Edited 1 time(s). Last edit at 06/17/2014 11:20AM by Moderator.

One more consideration, what amount of cubic inches, you have circulating on top of the pistons, has equal amount circulating, undernath. How/where is all of this transfer ? Food for thought. roverman.