Author Topic: Just when I thought I was Winning  (Read 2275 times)

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Offline Dilkris

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Just when I thought I was Winning
« on: Friday,August 23, 2024, 08:49:17 AM »
This is a bit like the "walking in sand story"  :(
Couple of days back I posted in the Members Cars section under the thread "Dilkris Update - Rolling on her Wheels" and all was looking good.
This engine has maybe a cumulative total of 2 ERH's on the clock, all done in high and low idle mode; she has been completely and comprehensively rebuilt by myself with the exception of 3rd party involvement for machining works. (Crank Regrind, Cylinder Liners, New Valve Guides, Valve Seats Cut and some machining to the inlet camshaft due to the alternator pulley having spun).
Due to P.O's and unknown history I rebuilt her with a 0.070" Cometic Head Gasket to compensate for previous head skimming. With regard to the head, the only original items are the head itself, camshafts and the cam follower sleeves.
All good you would think....  :-\
I have 180 psi compression across 4 cylinders (cold) and no oil burn on the plugs although they do show signs of running rich probably due to the engine running at idle modes only; running she sounds quite sweet.
My problem is I have an oil leak from the exhaust ports on cylinders 3 and 4 - 4 being the worse. (See photo's)
My thinking is that either:-
1. I have an exhaust valve guide issue on 3 and 4
2. The head is flooding with excess oil. (I have read and seen somewhere where auxiliary drains have been fitted to the head
    and also read where orifices are fitted in the oil feed in the block to reduce oil flow to the head. :confused:)

Anybody had this problem and any ideas?  :(                 
   

Offline BDA

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Re: Just when I thought I was Winning
« Reply #1 on: Friday,August 23, 2024, 09:52:28 AM »
Yikes!

I believe there is a vent  in the head that normally connects the head to the carb inlet box. Do you have that? Looking at your previous pictures, it appears to be covered...

Is any oil found on intake valves (although not seeing any may not mean much since it might be just sucked in and the oil wouldn't tend to be burned)?

Could there be an oil passage to the head near the 3 & 4 cylinders? Any evidence of that leaking?

You could do a leak down test looking for air going through your rings on 3 & 4.

Did you install valve guide seals? Are they in good shape?

Could there be a problem with your rings in 3 & 4? Ring gaps correct, Oil control rings properly installed, etc. I'm assuming your pistons are new and not worn.

I have seen many TC motors with extra venting from the cam cover - usually but not exclusively on race motors. I never paid that much attention to them but I now wonder if those were used because the normal vent from the head to the intake was blocked up since you would prefer not to sully your intake charge with oil vapors. It would not be a terrible idea to do the same but your motor shouldn't need it to prevent what you're seeing. One might expect all your guides to leak oil if that were the case anyway.

That's all I have at the moment...


Offline Clifton

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Re: Just when I thought I was Winning
« Reply #2 on: Friday,August 23, 2024, 11:17:03 AM »
This has a vent to manifold or atmosphere? Oil level not too full?

I've never changed guides to know if that can cause oil leakage. I know people change valve spring with heads on. I would try stem seals as it would be the easiest and go from there.

Offline Dilkris

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Re: Just when I thought I was Winning
« Reply #3 on: Friday,August 23, 2024, 11:39:21 AM »
Yikes!

I believe there is a vent  in the head that normally connects the head to the carb inlet box. Do you have that? Looking at your previous pictures, it appears to be covered...
 
Is any oil found on intake valves (although not seeing any may not mean much since it might be just sucked in and the oil wouldn't tend to be burned)?

Could there be an oil passage to the head near the 3 & 4 cylinders? Any evidence of that leaking?

You could do a leak down test looking for air going through your rings on 3 & 4.

Did you install valve guide seals? Are they in good shape?

Could there be a problem with your rings in 3 & 4? Ring gaps correct, Oil control rings properly installed, etc. I'm assuming your pistons are new and not worn.

I have seen many TC motors with extra venting from the cam cover - usually but not exclusively on race motors. I never paid that much attention to them but I now wonder if those were used because the normal vent from the head to the intake was blocked up since you would prefer not to sully your intake charge with oil vapors. It would not be a terrible idea to do the same but your motor shouldn't need it to prevent what you're seeing. One might expect all your guides to leak oil if that were the case anyway.

That's all I have at the moment...

Yikes indeed.....  :confused:
I'll try and answer your comments in order - (sorry - wish I knew how to do this properly.) Here goes:-
1. The vent is there - please see attached photo - it vents nowhere atm as I have no air box installed.
2. I have not checked oil on intake valves but suspect zero as I have no blue smoke form exhaust and no oil burn evidence on the spark plugs.
3. Not sure about your oil passage comment - I believe the oil feed to the head is from the timing cover side of the block (?)
4. I have not done a leak down test (don't have the equipment) but doubt oil passing rings as this would effect compression readings which presently stand at a healthy 180psi.
5. There are no valve guide seals on a TC lotus engine - unless modified at a later stage (which is not easy and quite complex)
6. Pistons and rings are new - STD - as I had the block sleeved.   
7. Agreed - why do I only have this problem on exhaust valves 3 and 4?
8. Not too sure if the works I have seen to heads is to increase venting or to improve the return of oil from the cam shaft
    housings back to the sump.
 
In conclusion, I do not believe the problem stems from the block - everything seems to point to the head.
I know the head is going to have to come off  :( :( - but I am trying to pin point what to expect.

Offline BDA

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Re: Just when I thought I was Winning
« Reply #4 on: Friday,August 23, 2024, 11:53:10 AM »
I’m afraid I have no better ideas…

You should know that compression and leak down tests are not really equivalent. A good compression test does not necessarily imply a good leak down test. A leak down test can give you a lot better information and they’re easy and inexpensive to make (https://www.lotuseuropa.org/LotusForum/index.php?topic=3696.msg39112#msg39112).

Good luck and tell us what you find out.

Offline Dilkris

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Re: Just when I thought I was Winning
« Reply #5 on: Friday,August 23, 2024, 11:54:15 AM »
This has a vent to manifold or atmosphere? Oil level not too full?

I've never changed guides to know if that can cause oil leakage. I know people change valve spring with heads on. I would try stem seals as it would be the easiest and go from there.

With an air box installed - the vent is connected to this and therefore the manifold - presently it vents to atmosphere.
Oil level good
Changing valve springs without removing the head on a TC Lotus is something I'd like to see.
There is no facility to accommodate the installation of stem seals on these engines - please see attached.     

Offline Dilkris

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Re: Just when I thought I was Winning
« Reply #6 on: Friday,August 23, 2024, 12:01:23 PM »
I’m afraid I have no better ideas…
Good luck and tell us what you find out.

Thanks for your input BDA - the first stage will be to take the head off and see whether there is anything obviously amiss. Sending the head off to be pressure tested could well be on the cards also.
These are the challenges faced when buying a car that was in pieces.  :confused:
Will keep you posted.   

Offline TurboFource

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Re: Just when I thought I was Winning
« Reply #7 on: Friday,August 23, 2024, 12:30:17 PM »
CWTech had the head on TCST machined for valve guide seals .... so I installed new ones with the new valves etc. Not much room for them!


I have some anxiety about starting TCST so I feel your pain!!!
The more I do the more I find I need to do....remember your ABC’s …anything but chinesium!

Offline jbcollier

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Re: Just when I thought I was Winning
« Reply #8 on: Friday,August 23, 2024, 08:53:28 PM »
My former boss has a habit of putting piston rings in upside down.  Nice guy otherwise.  The engine then pumps oil up into the combustion chambers.  Many rings are symmetrical  but some aren't and it is important to fit them correctly.  When you pull the head, if the cylinders with the "oil leak" are clean and wet, that might  be your issue.

Otherwise, valve seals as you suspect.

Offline EuropaTC

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Re: Just when I thought I was Winning
« Reply #9 on: Friday,August 23, 2024, 11:21:47 PM »
Hmm, that's an interesting discovery, or as most folks would say "a real bummer".

You're right on the oil feed system and frankly I can't see how oil would end up where you're finding it under normal conditions.  The feed is the front (diagram below), it goes into the cams and then floods the head. If there was a leak at the block/head interface then I'd expect to see oil outside the block, not coming out of #3 & #4 exhausts.

Although there's a drain from the head to the sump and a vent to atmosphere, both of which you've shown are in place, there's still a reasonable pressure in cam covers. If you're curious, take the filler cap off when it's running and stand back.....    (no, don't try this at home, it will get messy)

So the cam followers are always flooded and even with vents in place there's enough pressure to find any weak points - look how often you see TCs with cam cover gaskets/cover nuts misted with oil.

As you're not burning oil then my first thought would be exhaust valve guides.  As you say there's no seals and it's all down to machining the exact tolerance required so in theory one or two could have been reamed incorrectly. But that's a long shot, if all the guides have been replaced there's no logic that says one or two would have been machined differently to the others.

The other option, even more obscure, would be an incorrectly machined valve stem, again I can't offer that with anything other than the 1:1,000,000 chance of being right !

So if it's machined correctly then I'd look at the cam followers and sleeves.

They don't usually wear because they run in oil and on the early heads in fact the followers didn't have the sleeves the later ones had, but the oil is getting into #3 & #4 exhausts somehow.

I have read somewhere about keeping the followers in the correct order when you get the cams off and making sure they go back into their respective sleeves, so maybe there's a wear pattern involved. I honestly don't know and the reason might be the cam lobe/follower interface and nothing to do with the follower/sleeve interface, but I'm throwing that one in as a freebie.....

Personally I'd run it a bit longer and give it a few more coats of "thinking about" before pulling the head, ever hopeful that it will go away. Yes, I'm an unrealistic optimist at times.

If the oil is annoyingly persistant then I think my first move would be to look at the cam followers,  lift the cams and measure the followers and sleeves on all the valves to see if some are better than others.   If the followers are slack in the sleeves on #3/#4 then I could see more oil getting to the backs of the guides than on #1/#2, and I'll bet there's enough pressure from the cam cover and pumping action of the follower to push it down the guide into the exhaust port. You wouldn't see oil burning because the valve is only open when gas is flowing out

If all sleeves are identical spec then it's head off and finding somewhere who can pressure test it on the bench.  I think I'd ask QED myself, they have a long history of TC heads so they might have seen similar and perhaps even a weld repair ?

Fingers crossed that swapping cam followers around fixes the problem.....

Brian




Offline GavinT

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Re: Just when I thought I was Winning
« Reply #10 on: Friday,August 23, 2024, 11:59:46 PM »
Presumably the crankcase vent can be confirmed to be working while the engine is running? It looks pretty clean in the pic which could indicate good minimal blow-by or, alternatively, a blockage.

Got a pic of the plugs?
If they are all clean to the same extent, doesn't that kinda say the oil isn't travelling up from the cylinders? In my mind, that seems like a lot of oil for an engine that's only run for ten minutes.

If you have one of those borescopes that attaches to your phone, that might be interesting. I'm thinking brand new pistons should still be pretty clean given the minimal engine run time.

Failing that, there's only one other path the oil can take to get into the ports - valve guides.
It still seems odd this only affects 3 and 4. Does the Twink have a tendency towards oil gathering around that end of the head?

Offline EuropaTC

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Re: Just when I thought I was Winning
« Reply #11 on: Saturday,August 24, 2024, 12:35:01 AM »
Failing that, there's only one other path the oil can take to get into the ports - valve guides.
It still seems odd this only affects 3 and 4. Does the Twink have a tendency towards oil gathering around that end of the head?
Could be, having accidentally left off the filler cap and then running the engine I can say you get plenty of spray coming out from the exhaust cam and the cap is at the back.

The drain/sump return pipe and vent is on the inlet side so the obvious return for oil from the exhaust cam shells is along the head to the front and down timing cover. I'd expect the pressure to be equal on both sides but you've got a point, there could easily be a slower oil return/higher level above the followers on the exhaust side of #3/#4.

Brian

Offline Dilkris

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Re: Just when I thought I was Winning
« Reply #12 on: Saturday,August 24, 2024, 02:32:02 AM »
Quote EuropaTC: "If the oil is annoyingly persistant then I think my first move would be to look at the cam followers,  lift the cams and measure the followers and sleeves on all the valves to see if some are better than others.   If the followers are slack in the sleeves on #3/#4 then I could see more oil getting to the backs of the guides than on #1/#2, and I'll bet there's enough pressure from the cam cover and pumping action of the follower to push it down the guide into the exhaust port. You wouldn't see oil burning because the valve is only open when gas is flowing out."

Thankyou everyone for taking the time to comment - my thinking is along the lines of the above. I have good compression (180psi) and no blue smoke so I do not believe the oil is actually entering the combustion chamber via either the inlet valves or via the bores; it is entering after the exhaust valves (so to speak) in the exhaust port area of the head and the only way it can get here is via the valve guides - or, (god forbid), a crack. 
I have not performed a leak down test as the 180psi compression suggests no bore or exhaust/inlet valve seat problem - or is this thinking wrong?
Looking back on what I ordered and replaced during the rebuild of this engine I notice that I replaced 5 of the 8 cam followers due to visible scoring on the face of 5 of the followers - I did not replace any cam follower sleeves as not only did their appearance seem healthy but the machinist who replaced valve guides and recut the seats said the sleeves (which were/are readily available) were a nightmare to change.
As already highlighted, excessive clearance between the sleeve and follower I guess would allow the valve spring chamber to fill with oil upon which the cam follower would then act as a piston forcing oil down the valve guide.
Everything considered, this honestly appears to be the most plausible cause of my problem.
I hear you - QED are the "go to" people in this regard with provenance second to none, but my money tree is not doing so well at the moment.
I'm going to close the thread now, (thankyou all once again) and report when I know more and hopefully tell you what it was.....             

Offline BDA

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Re: Just when I thought I was Winning
« Reply #13 on: Saturday,August 24, 2024, 05:37:48 AM »
The reason I suggested a leak down test is to see if you had excess leaking through your rings. It was a long shot but I was out of ideas.

I think a leak down test is better than a compression test because it is static so not dependent on how fast the engine was being cranked. Also I think you could get a momentary high pressure that the compression test would register but you could still have excess leaking. A leak down test will also allow you to pinpoint the leak (which valve, if rings, if head gasket) and also get an indication of how bad it is. 180 psi is very good compression which I would think argues that there is no combustion chamber leaking but I also think doesn’t necessarily preclude the possibility for the reasons I’ve mentioned.

Having said all that, I think EuropaTC probably has it right and rings are not a worry otherwise you’d be burning oil.

Offline dakazman

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Re: Just when I thought I was Winning
« Reply #14 on: Saturday,August 24, 2024, 07:13:48 AM »
  Turbo,
 I try to stay out of the TC conversations but I hate this one step backwards. 
What kind of run-in did you give the motor , RPM, Time, and total runs?  If am out in left field , Please ignore.
 Before pulling head I would try to clean up as much as possible and install new plugs and run again.
 unless you think Its gonna hurt the engine further.
Dakazman