Non-Alfa but still Italian (HELP!)

[Nick Koleszar <koleszar@xxxxxxxxxxxxxx>]

Here's a poser for the mechanically experienced.

I have a Lancia Y10 Turbo. Probably unknown to North Americans and even 
pretty rare in the UK.

It suffers from a misfire at idle which clears up over about 1000 RPM. The 
problem seems to be linked to lack of compression on one of the end 
cylinders. The compression is 140 - 150 for the two middle cylinders and 
about 100 on the end cylinders.

As a result of a rally-style run (ie. 50-60 mph on backroads in pouring 
rain at night) to the middle of England last weekend and the unfortunate 
discovery of about 18 inches of water on one road, I had to have the 
gaskets on both intake and exhaust manifolds replaced. A new head gasket 
appears to have fixed the poor driveability experienced post-puddle.

The head has been fully-checked, the valves are fine as is the valve-train, 
there is no sign in the bores of broken rings. All electrics seem fine.

Here's the hard part (for us atleast): the unequal compression (across the 
block) disappears at 1500 rpm at which point all 4 cylinders give readings 
of 150. The turbo (very much the old-skool on/off implementation) doesn't 
start to puff until 3000 so we are in the dark.

Anyone have any ideas? Warped head?

+++++++++++++++++++++++++++++++++++++++++++++++++++++++
koleszar@domain.elided	NICK KOLESZAR

------------------------------