Oil leak and Breather

[LCRJ]

Hi all,
My Lotus TC has a little oil leak from around the crankshaft pulley.
I can see a little oil drip from the middle of the half round section behind the crankshaft pulley and
oil splash from right side. I did to tighten the bolts of the sump.
It seems to the leak from front oil seal. But it?s not old.
I found the oil leak when over 4500rpm. Is it normal?
Maybe my crankshaft pulley has worn out.
How about your engine over 5000,6000rpm?
I?m thinking add extra breather from front of cam cover if it?s good solution.
Please advice me about the oil leak and extra breather.
Thank you.
Hiro

[rgh0]

Hi Hiro

The twin cam engine can certainly pressurize its sump and leak oil out the front seal when used at full throttle for extended periods at high revs. A breather on the front of the cam cover as done by many racers can help reduce this pressurization and leakage.

Keeping the front seal centered on the crank also helps minimize the leakage. The front cover can move about overtime as it is not doweled in place resulting is excessive run-out of the crank shaft versus the seal and leakage. I use a round section of aluminium with its outer diameter the same of the front cover seal opening and its inner diameter the same as the crank shaft to set and also check the centering of the seal and to hold the front cover in the right location and make sure it does not move when bolting down the head.

In addition vibration of the crank shaft and block around the nose of the engine at high revs also seems to promote leakage. Not much you can do about that though I have seen people try crankshaft vibration harmonic balancers from cars like Minis to try to reduce it.

cheers
Rohan

[LCRJ]

Hi Rohan,
Thank you very much for your input every time.
You can say my oil leak is normal for standard engine?
Yes, the oil leak(I would like to say oil splash) is very little.
But I would like to stop any oil leak if possible. I think a clean engine has the best performance!
Actually my front oil seal is new and crank did checked a valance then built by professional here.
If I can stop the oil leak, I will add extra breather on the front of the cam cover.
Also will try to new crankshaft pulley. What do you think?
Now I use an electric fuel pump. So I add extra breather from the fuel pump. But It?s seems not enough.
Maybe it's ineffective?
I can see many race engine have one. But I prefer original looks.
Original Works cars did not has extra breather from front of the cam cover at that time.
Do you have any good idea, solution and special parts?
What is crankshaft vibration harmonic balancers?
I very much appreciate your help. Please tell me if you have tips.
Speak to you soon.
Hiro

[rgh0]

The leakage from the front seal is normal for a twin cam used to its full performance. The amount of blow by gases increases rapidly with engine power output and thus the engine pressurizes more at high revs.

My Elan race engine does not leak on short tracks with limited time at high power and high revs.. However on the Philip Island track with it long straight and long period at 8000 rpm and full power it develops a leak from the front seal despite having a large breather off the front of the cam cover.

A new pulley may help if the seal surface on your current pulley has wear.

A breather from the fuel pump opening will help but it will gets lots of oil spray into it. The added breather needs to be around 15 to 20 mm diameter to vent the blow-by gases adequately and prevent pressurization of the block.

A harmonic balancer has an outer steel ring separated from an in steel hub by a layer of rubber. Some engines use them as standard but their use on twin cams has not been proven to be beneficial enough I believe, otherwise more people would use them I think.

No special parts or easy solution just:
1. build the engine to minimise blow by and balance the engine well to minimise vibration
2. centre the front crank seal on the crankshaft when assembling the front cover and head on the block
3. Put as big a vent pipe as you can on the engine to a catch tank or back to the carbs inlet

cheers
Rohan

[LCRJ]

Hi Rohan,
Thank you for the information.
I will check my crankshaft pulley first.
Then I will add extra breather.
When did the extra breather appear? I?ve never seen period pictures.
However the oil leak just coming over 4500rpm. It?s far from full performance.
Just in case, Can I easy to change to new front oil seal? I have to remove front cover?
Thank you again for your help.
Kindest regards,
Hiro

[RichardHawkins]

Hiro,

When I was installing the front cover, I did as Rohan and made a bush to fit where the seal goes in order to centre the cover on the crankshaft. If I remember correctly the SKF catalogue recommends a maximum permissible eccentricity of 0.002". I also noticed that the crankshaft pulley was only feeling like a good fit because it fitted the key. With the key removed the pulley was slack. With the key installed the pulley was eccentric on the crank.

Richard Hawkins

[rgh0]

Hi Rohan,
Thank you for the information.
I will check my crankshaft pulley first.
Then I will add extra breather.
When did the extra breather appear? I?ve never seen period pictures.
However the oil leak just coming over 4500rpm. It?s far from full performance.
Just in case, Can I easy to change to new front oil seal? I have to remove front cover?
Thank you again for your help.
Kindest regards,
Hiro

I don't know when extra breathers first appeared but i have seen them on mid sixties photos of race cars so it looks like racers soon figured out they needed extra breather capacity.
My Elan engine tends to leak a little above 7000 rpm when at full throttle for an extended period down a 1 plus km straight, so yes a leak at 4500 rpm you should be able to stop.
You can pull of the pulley and replace the seal with the engine in the car, you dont have to remove the engine or front cover. Be careful when refitting the seal as there is no lip on the front cover hole to stop it going in to far. Tap it into place gently until it is flush with the front of the front cover.

cheers
Rohan

[LCRJ]

Hi Richard and Rohan,
Thank you for the information.
I will check my crankshaft pulley first.
Also the front cover position if pulley is does not have a problem.
Rohan, Does your Elan engine has extra breather from front of the cam cover?
Today I exchange a cam cover with extra breather.
I would like to see How it works. Maybe it's ineffective for 5000-6000rpm fast road use car.
Speak to you soon.
Hiro

[rgh0]

Photo of my breather.

This is a 1/2 inch 13mm internal fitting and hose. I have since replaced it with a 3/4 inch / 19 mm fitting and hose for improved vent flow at full throttle and 8000 rpm revs which helped

cheers
Rohan

[john.p.clegg]

Also by Vegantune

John

[LCRJ]

Yes, also my VEGANTUNE too! Hiro