compression ratio

a basic question that has had me scratching my head! no pun meant.

my ponderings are as such. according to all searches the blocks are the same for the 2.25 petrol and diesel, the bore looks to be the same as does the stroke. now as far as my knowledge goes, the compression ratio's are different, is this achieved in the head and head gasket alone,

further reading tells me that the 2.5 td came in a petrol variant, is the compression change achieved in the same way? the reason i ask is that i have a 2.25 diesel with a naffed block and a 2.25 petrol that is good. will swapping the heads ( and ht system and manifolds) work? please can someone tell me how land rover managed to lower the compression!!?!?!

cheers

2.25 engines and 2.5 petrol or diesel do share a common block depending on 3 or 5 brg,all bores are the same upto and including 300 tdi ,on petrols compression ratio is done through head,combustion chamber ,skimming will alter compression ratio if enough removed,petrol heads are obviously totally different,there was never a lr 2.5 petrol td,they at time of td only made td blocks and fitted bungs in turbo oil holes for other engines

sweet thank you for the speedy reply, i knew they did not do a 2.5 turbo petrol, but read somewhere that a 2.5 petrol n/a was at least thought of. but back to the point, if i was to put the head for the diesel onto a petrol block it would work? or is milling required?

no ,no combustion chamber ,so very high compression ratio ,spark plug holes ,hot spots etc,2.5 petrol looks like 2.25 petrol with better carb