Achieving a leak free engine

[JonB]

Hi!

I want to solicit ideas about how to build an engine up so it doesn't leak oil.

Some years ago, I partially dismantled the Twink in my (now sold) Plus 2, with a mind to fixing all the oil leaks. I had a copy of Miles Wilkins' book in one hand, and a head gasket & bottom end set in the other. I followed all the instructions I found in Miles' book, which assures the reader it is possible to prevent oil leaks on a rebuilt engine.

Well, none of it worked. Shortly after rebuild, it started leaking again, and from "the usual places". I'm pretty sure that this depressing outcome was part of the reason I sold the car.

Fast forward a few years and I find myself in a similar situation. I have a reasonably low mileage engine (65k) down at the machine shop getting a .020" rebore and balance, and soon I will be reassembling it. I do not want a repeat of the last outcome! Yet, I believe that doing it per Miles Wilkins' writings is not going to improve matters - unless I dod "something" wrong? I'm seeking a more modern approach... or ideas at any rate.

What say you all?

JonB

[alan.barker]

Good luck Jonb you'll need it.
The minimum thing to do is Lap all joint surfaces using a very good flat surface and wet and dry.
Degrease all surfaces with Acetone after. don't overtighten any Screws/Bolts or Nuts.
see what Rohan suggests for the Sealant.
After assembly give it 2 or 3 Coats of Ferguson Tractor Paint. this bridges across all Joints/Seams.
If it leaks after that sell it and buy a MX5 ( Elan Copy no leaks and cheap as Chips)
Alan

[JonB]

Alan, I will never buy an MX5.

[tonyabacus]

Jonb
Whilst you engine is being done, ask them to sit the block on a large surface plate and check the flatness of the sump face and also do the same with your sump. Sometimes the bolt holes in the sump can become distorted and prevent a truly flat surface.

If the reborer does not have a plate then most engineering shops have them in different sizes and will do a check for you. Whilst you can try checking with steel rulers and strips of steel, these methods are not as definite as those from a surface plate, which will give you a much better chance to be leak free. Did I mention seal surfaces (is yours a 4 or 6 bolt crank) as theses too need checking to ensure they are good and sound.
Tony

[alan.barker]

Alan, I will never buy an MX5.

I bought a BMW Z3 2.2 litres a few weeks ago it runs very well indeed. Very solid
Alan

[JonB]

Alan, I will never buy an MX5.

I bought a BMW Z3 2.2 litres a few weeks ago it runs very well indeed. Very solid
Alan

I feel your shame, Alan.

[JonB]

Jonb
Whilst you engine is being done, ask them to sit the block on a large surface plate and check the flatness of the sump face and also do the same with your sump. Sometimes the bolt holes in the sump can become distorted and prevent a truly flat surface.

If the reborer does not have a plate then most engineering shops have them in different sizes and will do a check for you. Whilst you can try checking with steel rulers and strips of steel, these methods are not as definite as those from a surface plate, which will give you a much better chance to be leak free. Did I mention seal surfaces (is yours a 4 or 6 bolt crank) as theses too need checking to ensure they are good and sound.
Tony

Good call,Tony. I think the main issues come at the cam chain / water pump plate to timing chest interface. You have a 3 way join there. My sump never leaked. Although the timing cover did, a little bit. This time round I’ll be fabricating a baffle to sit under the oil filler cap, as my previous Twink liked to leak a bit there, too. Ah, also, it seemed to have quite a puffy breather, despite good compression figures and zero exhaust smoke.

I’m hoping with new pistons, rings etc that blow by will be reduced. Crankcase pressure being a contributing factor of course…

[alan.barker]

Alan, I will never buy an MX5.

I bought a BMW Z3 2.2 litres a few weeks ago it runs very well indeed. Very solid
Alan

I feel your shame, Alan.

Mmmm i'll see in May and June how the 5 weeks Tour of Ireland and Scotland goes with the "shameful Z3".
The last and only time i did it in an Elan +2 was a Nightmare. Water Pump letting go and Tripanning the Rad. All rebuilt at the side of the road. That was in 1977.
Wait and see.
Alan

[JonB]

I’m sure it will be fine, Alan.

We are getting a bit off topic though…

[alan.barker]

Yes,
For sealants Rohan put alot of info.
If good enough for him Racing should be ok for road.
Alan

[h20hamelan]

Head and sump pressure to catch can

[trw99]

All I can add is that it is possible to have a leak free twin cam. My Sprint has one.

However, I take no credit for that. That goes to George Wadsworth, who I asked to rebuild the engine to original Sprint specs around 9k miles ago.

The engine uses less than a litre every 3-4k miles and seems as tight as it was when I saw George test it on the dyno.

Tim

[reb53]

Watching an Ivan Dutton "Shed Racing" youtube video a month or two back.
Ivan was wanting to lessen the leaks from, I think, his Hall and Scott aero engined car.
The suggestion of one of his followers was to put a one way valve on the engine breather to allow pressure out, but not in. This being an attempt to have negative crankcase pressure, which should help alleviate leaks.
Which it did once Ivan made, and fitted, one.

The breather on my engine goes into the airbox and I wondered if putting a valve on there might improve things.
Anyone tried it ?

I might add that I've never seriously attempted to make my engine oiltight, keeping it running well is enough of a mission....
I do carry a fold up plastic drip tray that I slip under the car on the odd occasion I have to park on a flash driveway.
The amount that actually drips out whilst driving is inconsequential in the grand scheme of Twink oil usage !

Ralph.

[tonyabacus]

JonB set me thinking, whilst it is not quite so common, the leak from the oil filler cap has been an issue on occasions. Somewhere on the Forum I recall reading an article on it with one or two good modifications to prevent oil from splashing up and leaking out from the cap. I cannot remember how long ago I read it but I am sure a searech should bring it up.

Also it does depend on using the correct sealants in the correct places, but that does not mean splashing RTV everywhere

However, it does also depend on which end of the engine the oil appears to be coming from which will point you in the right direction to find it. JonB is also correct with the water pump end. If the engine is apart then check the sealing faces by placing th pump plate and front cover (minus the rotor) on a piece of glass and run a thin feeler gauge between the body and the glass to check it is flat with no obvious big gaps that might give rise to a leak.

Any high spots can be taken down by using a sheet of 3/4000 grit wet and dry between glass and pump body, checking frequently. You can also make your own gaskets out of thicker gasket paper which is available from most engineers suppliers, but remember the surfaces still need to line up, so the paper thickness does not want to be any more than double the original.
T ony

[StressCraxx]

If I could add to Tony's great advice for checking and correcting the timing cover/backplate flatness...

From an expert engine builder...
Take a flat whetstone over the face of the block at each drilled/tapped hole. Over the years the tapped threads on the face of the block tend to "pull up" away from the face of the hole just a few thou and keep the gasket and backplate from fully contacting the block face.

I also learned to do this on the face of the crankshaft flange and the face of the flywheel before sending both off to the balancer.