5 replies to this topic

[DeadSquare]

Last month a chap called and asked if I knew what the noise was in his daughter's 40+ year old, 'barn-find', Mini.  I didn't really need to go 100 yards to confirm that with out lead in the fuel, I would diagnose 'pre-ignition'.

 

I have done the usual timing / mixture things, but it's still there, so last night I removed the head, expecting to see a massive de-coke needed.

 

Instead, the head is nicely profiled with polished ports and larger valves, but heavily shaved.  It is also obvious that although the block and the log book say 998, it actually has an 1100 crank.  I haven't measured the combustion volume, but It looks as though the head came from a hot 850 and I recon that the C/R could well be over 12:1, so it needs a decompression plate or maybe three very thick gaskets.

[whistler]

I know they're expensive but Cometic make various thicknesses in head gaskets.

[Shooter63]

The Victor Reinz gasket has around 3.5cc capacity, may be a bit more, which is I believe the biggest without going down the specialist route. Can you not ease the chambers to gain more capacity?

Shooter

[DeadSquare]

Thank you for your suggestions.

 

I used to have, or can't find, a large ex-WD  "Q-Max" 2.5" , punch and die hole cutter, that with plenty of lubrication would just cut 1/8" aluminium.

 

The 63.5mm hole was ideal for decompressing supercharged, small bore A series.

[timmy850]

Vmax sells decompression plates for small bores. I haven’t been able to find any thick Cometic small bore ones

You can also use two head gaskets

Or another option is a good supply of octane booster

[mini13]

yeah... i would try to avoid thick gaskets if possible, but that said i have run 2 gaskets on a 1380 turbo motor with no problems