Achieving a leak free engine

[wdb]

The twincam in my Caterham is lot drier since I put a dry sump on it. I believe it is due at least in part to the presence of the scavenge pump, which is constantly pulling oil -- and air -- out of the crankcase.

[rgh0]

this post is a good starting point on sealants and gaskets.

viewtopic.php?f=39&t=41344

As others have mentioned you need to ensure that all mating surfaces are clean and flat and have not pulled up around bolt holes.

You also need to ensure that the front and rear crank seals are centred on the crank. The front really needs an alignment tool that fits the crank and the front cover opening so it holds it central while you do up the bolts. I leave this in place while fitting the head to ensure it does not move when the bolts at the front of the head is tightened. The rear is easy enough to check the housing is central by using a digital caliperto ensure the gap is even between the crank and seal housing before tightening the bolts. The rear seal normally does a good job a self centering the light housing on the shaft and you really just need to ensure you dont move it when tightening the bolts.

cheers
Rohan

[Hawksfield]

Jonb
Don't despair they can be oil tight. I rebuilt my +2 back in dec 2021. And it is still oil tight.
The secret is a number of detail points.
1. Refer to Rohan's advice.
2. Check the contact rubbing area on the rear seal. I increased the gasket thickness to give it a new rubbing area.
3. Careful fitting of crank half-moon seals I used hard rubber seals from classic gaskets uk. Ebay.
I centralized the the front cover using a new seal filled with araldire when hard I pushed in part way with the pully to centralize it, this can be removed when fully bolted.
4 ensure the sump is even around the bolt holes, I had to hammer some of mine to get a level surface.
5 Don't tighten the inner front cover single bolt till all the front bolts are in. And nipped up. I left it over night.
I will look for the images I took and post

[2cams70]

Alan, I will never buy an MX5.

Agree - don't support those who copy and especially those that don't acknowledge where they got their inspiration / ideas from.

Where did the engine you rebuilt a while ago leak from specifically? It's difficult to provide guidance without this information as there's just so many areas a leak can sprout from. Knowing this we may be able to better determine where things went wrong first time.

[JonB]

From the normal places - filler cap and front timing chest / water pump housing interface, mostly. I don't recall the sump seal leaking, or front / back crank seals.

Edited to add, as you can see, I've been here before...

viewtopic.php?f=39&t=41496

Also, link to a fix for the oil filler cap: http://www.lotuselan.net/forums/lotus-t ... ml#p210521 (as I am reviewing my previous thread).

[tonyabacus]

Perhaps I can add to StressCraxx input and thanks for the reminder.

In my haste, I forgot to add his additional information in my original response but concur with all he said. In fact I do this on all the bolt holes on the block as well as some of the fittings. It is surprising how often this "pull through" can happen, so imagine what has happened to the two surfaces involved, especially if one surface is aluminium. Another area of leaks that has been mentioned in the past is the cam covers, where again placing it on a flat glass surface and using the feeler gauge method, will likely show up any irregularities.

These engines can be made leak proof but need some forethought regarding the mating surfaces and cements used. Once in use it is worth keeping a check around the fuel pump, distributor shaft, oil filler cap, breather tube and dipstick hole (I sometimes use a thin rubber washer or piece of rubber on the stick here to prevent any oil escape. For some reason this seems to affect the odd engine or two, perhaps due to abnormal crankcase pressure.

There can be an issue with oil seepage at the flywheel end on some early 4 bolt engines, but again with care during assembly this can also be eliminated. Finally remember to go round all the bolts with a torque wrench once the engine has been run a couple of times and got warmed up. No matter how good we are at thinking we can "feel" the right torque, a torque wrench will ensure they are all secured to the correct poundage.
Tony

[alan.barker]

I think the Twinks need more Crankcase Breathing.
I thought a few times in the past to drill and Tap a hole in front face of Camcover. To fit an Elbow and connect to breather/catch Tank. But i was never convinced it would look very good or professional.
Alan

[Hawksfield]

JonB

See my previous post.
viewtopic.php?f=39&t=51159
Never had a problem from crankcase compression at filler cap or cam cover or any where else.
Hope you have success.

[JonB]

Hi John

That's brill, thanks!

JonB

[RichardHawkins]

Jon,

I have just re-read the posts on your topic and was reminded by “twin cams” of the load placed on the timing chain cover by the belt that drives the dynamo (alternator on my engine) and water pump. I have used a different method to tension this belt, which I have braced directly off the cylinder block. I am reluctant to mention this mod, which I hope is an improvement, as my engine is part of a long term restoration and has not run yet. My other reason for reluctance is that I can’t remember how to post photos but hope that the work being done by Jeff will soon help.

Happy new year,

Richard Hawkins