Before I replace the engine I want to pretest for oil leaks. I'll need a very thin liquid that won't damage the engine and replace with proper oil when completed. Sounds crazy perhaps but any suggestions gratefully accepted.

Diesel fuel. If you are not going to run it. What's left will mix with oil when you're done playing.
It's a slight lubricant in itself, the first pre ww2 rail motors (Detroit Diesels) in NSW used it as ATF in their 2 speed automatic transmission. Normal ATF hadn't been invented yet.
(Source- I did my apprenticeship there in the mid 60s)

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

A proper automotive smoke machine will pick almost all leaks, not sure how it goes for something like weeping out of side cover type of cork leaks. You may be amazed where it pours out. Do it with carby/ manifold on.
cheers Lindsay Siebler

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1959 Austin A40 Farina fun car
1965 Mk1 Cooper S restored
1970 Colt 1100F SS restored
2014 Mitsubishi Imiev fully electric daily driver
1948 Allard M coupe Olds 215 v8 project
1971 Twin cam Escort ex Uk championship winning rally car project

Until this post I’d never heard of such a piece of test equipment on a vehicle. A quick Google search produced a number of advertisements for the machine itself and videos on its use. Most seem to be just a few hundred dollars.

Here’s an example - https://www.vevor.com.au/fuel-leak-dete ... 0246924081

Thanks for the post Lindsay.

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ex-NSW Police 1970 MK II Cooper S
VMCI #43

Hi Doug, I have been guilty of many a budget machine for just the one off job, but I have tried the disco fog machine and the proper auto one, and it was a bit like a 400m trench 1m deep with shovel or excavator !!!!!!. I have vevor toys, not the real thing. cheers.
If that engine is out of the car, I would suggest if you want to pre empt leaks, side cover gaskets leak often, diff oil seals, timing case oil seal and if timing chain is slack fit a new chain and a bit of instant power as cam timing will go closer to where it should be, and earlier cam gears with tensioner rings will advance it a bit more.

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1959 Austin A40 Farina fun car
1965 Mk1 Cooper S restored
1970 Colt 1100F SS restored
2014 Mitsubishi Imiev fully electric daily driver
1948 Allard M coupe Olds 215 v8 project
1971 Twin cam Escort ex Uk championship winning rally car project