It comes to all of us in the end! I have oil leaking from the front of the block to crankcase joint on the Chummy. I am trying to get away without having to take the engine out this side of the rally season, has anyone had any experience of a modern product that can be run in a bead around the outside of the joint as a temporary bodge? I understand that there may be a Loktite product that that is made for this type of repair, anyone know what it is called? In the past I have stopped these types of leaks on moderns with Evo-stik Impact adhesive painted along the joint. What is the most reliable modern sealant that most people use today when fitting the block during a rebuild? I am sure things have moved on since my ‘red Hermitite’days.

Tongue in cheek, I know Ian, but you have checked all the bolts to Crankcase are tight, that front ones a xxxxx anyway, but just a thought after one down and halfway through another Glen Ranoch Single Malt from Tesco's (at £8.99, I'm not to worried about the finer points of single Malt's) - medicinal purposes only, I seem to have caught a cold - something as inaminate as a cold, how do you hold on to one.

Ian, there are things out there, but the Red stuff's alright and still available. Your a traditionalist as I recall, so stick with it.

Phil, wheelchair Austineer...

Ian

One problem you may have is getting the surface "clean" enough i.e well and truly degreased. You will clean the outer surface, but oil will probably still be trapped in the joint and will seep out into and possibly affect the sealant you choose to use?

I have used blue RTV (room temperature vulvanising) in the past for something similar with mixed results. RTV sets like rubber and can in fact be used to make gaskets, so it would flex with your block/crankcase. It is also available in "orange", which is the high temp version which I have used when assembling exhausts with good results.

I guess if you emery papered up the surfaces to get a good key it might work, although to be honest I'm not convinced. How bad is the leak? The Colander true to its name has several leaks in this area along with plenty more elsewere!!

Regards

Steve.

Ian. I used Hylomar on the joint itself and then when assembled, a bead of silicone sealant all round the joint called 'Gastite' made by Tetrosyl and available at good motor factors. Heat resistant and oil resistant and the engine is as dry as a bone. (On the outside of course!)

May I endorse David's Suggestion. I use blue hylomar as well on the gasget and just before I lower the block onto the crankcase i put an 1/8th inch bead of automotive silicon round the edge of the gasket.100% sucess so far.. I still secure the block with the Barrel type nuts in the Valve chest chamber , but use self locking nuts on the rest.May I also raise the point that it really important that the bolt that locates the cam shaft bearing is tight and well sealed. I use p.t.f.e tape on the thread and a hard fibre washer under the head. Mac

This is probably "old hat" to "old hands" such as Ian, but for the benefit of newer people to the fold, much if not all of an oil leak between the block & crankcase is caused by flexing one to t'other, in turn caused by the flexing of the chassis. This problem can be helped if not entirely eliminated by loosening or even removing one of the front crancase mounting bolts, in Ian's case best under the mag. where you can't see it easily. This allows the chassis flexing to be taken up before it's transferred to the crankcase. Even on a racer with boxed chassis which is alleged to be rigid this works every time. A case of the horse & barn door? Hope this helps. Cheers, Bill

Hi Ian,
I am another hylomar user but usually I only put it on one side of the paper gasket to add to the compressibility of the gasket. As the aluminium expands at over twice the rate of the cast iron there will always be movement at this joint. The use of a 'setting' type gasket material like the red Hermitite will eventually lead to a leak as the material on one surface will crack away.

Over a 100 degree temperature rise the block will expand by over 10 thou. whilst the crankcase will expand by over 25 thou.

As to stemming the leak for the season, is it that bad? If the leak is caused by poor sealing rather than loose studs/nuts then it should not get too bad during the season and a simple wipe down after a run may be all you need to do. It has the added benefit of keeping the rust at bay!

I have often thought that a series of 'O' rings, into suitably machined seats on the crankcase or block should seal this joint and allow for movement, has anyone tried this?

Following on from Bill's point about chassis flexing twisting the crancase. When I bought my Chummy last year one of the rear engine bolts had been replaced by a longer bolt with a valve spring between the bolt head and the crancase foot. Apparently this had been recommended by an old Austin man to prevent (reduce?) crancase flexing. It seems to work as the joint is still oiltight - something previously unheard of in my 40+ years of Sevening.
Cheers Gordon

Thanks for all the input so far guys, just for the record I put the block on with Red Hermitite in 82 and it has been leak free until now, all bolts where tight, but it looks as though the jointing has had its day what with the constant expansion. The thing that is niggling me though is that the oil leak exactly coincided with the trial run of my new exhaust box (re. Earlier correspondence on this site). I can’t imagine that with all the ventilation in a Chummy crankcase through the main bearing/tappet cover/oil filler that the increased backpressure of the baffled box as opposed to the straight through is in some way pressurizing the crankcase. I might just change it back to see what happens. But the new box ‘is’ a great improvement so it will defiantly
be going back on after the test, leak or no leak!!!Looks as though it may be Evo-stik around the outside for now,will keep you posted

Hi Ian & all,

On the subject of the crankcase flexing I am just in the process of making a machined ali plate to fit on the bottom of the crankcase (to bolt to the surface the sump gauze fits on) with the aim of stiffening the crankcase in a effort to improve bearing life & stop the block/crankcase interface leaking or overstressing the studs. It should act like the like the lid on a biscuit tin and make the crankcase much stiffer in torsion (try twisting a biscuit tin with and without the lid on it makes a huge difference!)

It is a fairly simple job on the early sand cast coil crankcases (and probably the mag crankcases) as this surface is machined and the lugs round the bolts are fairly substantial, on the die cast later crankcases the surface is left as cast (would need machining) and the lugs are much smaller so I wouldn’t fancy trying this on a later engine.

The idea came from seeing a three bearing engine with a similar plate to support the centre main. (A Don Rawson engine I think).

It will be interesting to see if it makes much of a difference (if I ever get the car finished)

Regards

Rob