Cylinder block spacer plate

[Malcolm Parker]

As part of an engine overhaul I am in need of a laser cut plate 3mm thick to fit between the crankcase and block.   The engine has a Reliant SV crank and rods.  From memory I think the spacer plate is necessary due to the Reliant rods being slightly longer than Austin ones.   At present the engine has a home made spacer that is somewhat inaccurate and causing problems with oil leakage.
I note that laser cut spacers are available but only as shims 0.5 and 0.75mm thick.   Is anyone doing thicker ones?
If I used a Reliant SV block would this compensate for the longer rods?  I believe it is possible to modify the Reliant block by filling the distributor drive hole and machining it flat to make it look like an Austin one.

[JonE]

Malcolm - have you contacted the seller of a lot of Reliant race parts, including crankcases, presently on ebay very reasonably and went up yesterday I think. He may be able to help. (They are all in the 'Austin 7' search area)

[Stuart Giles]

Not sure that fitting an SV Reliant block would be simple or that it would solve your issue. the SV Reliant crankcase is taller than the A7 one to provide clearance of the Reliant big end bolts to the camshaft; so it's likely that the Reliant block is the same height as the A7 block. It's ages since I worked on one but I remember the cam followers being completely different to the A7 ones as they're a flat faced top hat type. The position of some of the Reliant cylinder head studs and waterways are transposed when compared to the A7 block.

[Alan]

It’s 30 odd years ago, Malcolm, but I recall taking the whole engine apart from the crank, rods and valve chest cover back to the scrapyard because none of it was going to fit. Can’t you compromise with two 1mm spacers and a bit off the piston crowns?

[Chris KC]

Malcolm, yes, Reliant rods are approx. 1/8" longer than Austin rods.

With respect, I agree that the plate itself contributes to leaks, mainly as it necessitates an additional joint face; but while it may look neater I doubt a laser cut spacer will leak significantly less than a carefully hand made part.

My guess would be that switching to a Reliant block will cause you more trouble than it's worth, I'd spend the effort making the joint as sound as I could manage.

Subsequent to the 10,000 mile record attempt in the late 70's, Chris Gould ran his Reliant crank car on Ruby con rods modified to reproduce the offset of the Reliant rods, I believe they are still in the car today (n.b. for the record attempt itself custom rods were made by Paul Bonewell). If that's a direction you'd like to consider I have some info on how Chris went about the modification. However the Reliant rods are very sturdy by comparison and for my money an oil leak is the least of the potential worries.

Plus I rather suspect you may spend a lot of time and money and find whatever you have done still leaks!

[Zetomagneto]

Is there sufficient material to shorten the Conrods at the big end

[steve anderson]

I use a water jet cut aluminum  ( ALI ) spacer ,  .078 thick ,in my Austin engine BANTAM with a silicone sealer , works great !!   Of course the surfaces have been milled , a big difference for leaks ..

[Malcolm Parker]

Thank you for your help and suggestions.   I have had a complete Reliant engine in stock for 30 years and to date the only bit I have pinched off it is the valve chest cover, which is on the Ulster engine, with the Reliant name filed off.
As regards the oil leak, I put up with it for at least 10 years and got used to having swabs of oil soaked rag stuffed between the cylinder block and the bulkhead, I thought it was coming from the valve chest cover but my friend who is doing the engine  thinks the spacer plate is mostly to blame.
I have a local engineering firm who do laser cutting so the next step will be to enquire whether they can cut me a plate using a base gasket as a template.
The Reliant con rods are nice things and I intend to keep them.   At present a Hillman oil pump is fitted (Avenger?) which required some modification of the crankcase.  Thoughts are that it is much too big for the engine and an uprated Austin pump could be a better bet.

[Chris KC]

Certainly if you can get laser cutting done easily it will do a neater job than drilling and filing. Note that the spacer is not usually the same shape as a base gasket, it has slots for the rods to pass through which are wider than the bores and which effectively replace the tin oil baffles. Also - importantly - in this conversion the cam centre bush is usually drip fed oil from the valve chest through a small hole between the valve guides, take care not to block it off with the spacer or any shim/ gasket; it's easily missed. You may find you also have an extra base stud.

My engines run on over-bored Austin pumps without problems - been over thirty years now. These engines don't seem to need as much pressure / supply as front-fed cranks.


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[Roger]

Malcolm,
I used an old base gasket to mark my spacer plate only to find it had shrunk over the time I had it.
I then marked the next spacer directly through the cylinder bores.
A fret saw was used for the cylinder holes and file to finish to size.
The others were drilled and a cone drill to expand them, all burs were then remove.
If you are careful the faces will not be damaged.
I had a contact that could have laser cut it for me but obtaining the correct dimensions and position of each shape takes time. It only took an hour to cut by hand.

Roger