Glad that Malcolm brought up the subject of "Sikaflex".
I'm still gathering info before deciding on the plan for the block/crankase joint, but one intriging suggestion I've been given by a black hand gang member is the use of Sikaflex by the racing fraternity.
I have spent sometime talking to people and re reading the usual well known Austin seven books etc and based on the general consensus I think Sikaflex or something similar may be worth further investigation?
If you consider what is or may be happening during use there are simply speaking two metals with different expansion rates joined together. HOWEVER it is not quite that simple. If you study the basic principles of Stress and Strain, Elastic Modulus etc etc it becomes apparent that it matters quite a lot whether or not they are actually joined really or whether there is movement. If you were able to well locate and fix the block to the crankcase perhaps by a glue of somekind and high tensile bolts you would set up different stresses in the block and crankcase, BUT the strain would be the same, you would in effect have two bars joined in parrallel. I reckon this would then result in distortion of the top face, because just maybe the stress in the crankase would be too much for its small section???

So to bring my rambling nonsense to a conclusion a lapped joint with no gasket BUT a sealant/adhesive such as Sikaflex would of course allow the different expansion to take place thus stopping the stress differences between block and crankcase. In the spec for Sikaflex 291 or 292 it clearly states it is designed to do exactly this!! Whilst remaining "adhered" to both surfaces (hopefully!).

I reckon doing this and perhaps diagonally bolting the engine to remove the twisting effect of the chassis would be well worth trying?

Some questions...

Has anyone used Sikaflex in this or a similar situation?

Sikaflex is used between -30 and +90 degrees, the engine will probably get at least this hot if not more?

Could be difficult to seperate the two if required??

Sorry to make a simple job so complicated, but I'm bored wating for the machining work to come back!!

Steve

Steve, I have only used sikaflex as a caulking material between floorboards which works well. Disassembly is with a circular saw.

Am I the only "old school " Seven owner to prefer a few oil leaks? I went to immense trouble to make my "box" tourer oiltight a few years ago with the consequence that I began having to pay attention to corrosion underneath. In the old days the only way you would find a rusty Seven chassis was if you hauled one out of a pond!

The subject of embrittlement of the chassis due to the carbon content in old engine oil has come up before. I suspect that by the time this is a problem there will be no carbon fuels in use!

I have friends who use that ferocious Loctite product (will find no. if you're interested) to seal block to crankcase, but I gather it's pretty final, so it's snip your oil baffles or omit them - but I believe it works.

Regards, Stuart

I've tried various products. My engine is, these days, in a trials car that does the full season of VSCC trials each year so they are subject to a 'significant' test. It is a solid foot crankcase and is bolted down firm at three corners but with an old clutch spring between the underside of the chassis rail and the washer/nut on the rear near side so it can flex slightly.

In the end, I have settled on the following method of sealing the block/crankcase joint.

1. Use new studs.
2. Ensure the threads in the crankcase are in perfect condition - helicoil if not.
3. Slightly countersink the stud holes in the crankcase (similar with the head studs in the block).
4. Use Loctite Studlock when you fit the studs to the crankcase.
5. Have a slight grind put on the bottom face of the block to ensure that it is true.
6. Lightly lap block to crankcase to ensure crankcase face is true.
7. Make the joint with Loctite 515 (this is the stuff Stuart refers to I think). Don't use any form of gasket.
8. Fasten the block down. Snip the oil baffles if you use them (I don't) so that you can fit the rods down the bores with the block/cranckase bolted together.

I used this system on my last trials engine that did 5 seasons of hard trialing with no oil leak whatsover on the block/crankcase joint. I stripped the engine this summer and the block came off with little effort. It now has a new block/pistons/cam etc. and makes its debut next weekend!!

Loctite 515 is not cheap - about £30 for a 50cl tube in the UK if I recall correctly but is excellent and a tube should last you years. In Australia, I think it was about Aus$15 five years ago. My Brother was visiting friends in Aus at the time and I arranged for him to bring me a tube back. The difference in price was beyond me given that 515 is made in the USA. As ever, what the market will stand I imagine.

STEVE

Quite right, Steve (J), it was the 515 I was thinking of. Very interested to hear that disassembly was OK.
I shall have to buy some 515 @ £30 + a can of Waxoyl for the undersides! This will cost twice what I paid for the car!

Still, I must admit no oil leaks block to crankcase is tempting....

Regards, Stuart

Thanks Guys

The loctite sounds interesting .

Stuart. just to clarify a point here I am of the same opinion as you regards oil leaks!! Just ask any Cornwall club members what my car looks like!! It has never been washed and I'd like to think it is "scruffy" looking, BUT my oil leak was SIGNIFICANTLY worse than all the other cars in the club. they all leave nice little drips here and there, but mine left a proper puddle!! It didnt exactly help the old car cause when I parked it in public!!

regards

Steve