R-R Merlin. One/two piece cylinder block

[lleullau]

I know that "the Merlin 61 was the first Merlin with two-piece cylinder blocks."(c) from British Piston Aero-Engines and Their Aircraft
But i'm see to the Merlin XX and Merlin 66 cylinder block and not understand where is the second part? They look exactly the same.

Merlin from Rolls Royce Merlin Maintaince Manual_Ser-66, 67,70,71,76,77, & 85

Merlin XX

 

[Crimea_River]

The cylinders and head are not broken apart in the first pic.

And, BTW, I know that that Packard Merlin 29 had the two piece cylinders.

 

[lleullau]

Many thanks!

 

[Bozothenutter]

So the later ones were monoblocks?

 

[pbehn]

So the later ones were monoblocks?

Other way around, if you want to make 1,000 Merlins a year you make it as a mono block, if you want to make 10,000 you make it with a two piece.

 

[Bozothenutter]

Other way around, if you want to make 1,000 Merlins a year you make it as a mono block, if you want to make 10,000 you make it with a two piece.

Ahh, got it now, seems my reading skills left me for a bit...20 is LESS than 66.....

 

[Deleted member 68059]

Other way around, if you want to make 1,000 Merlins a year you make it as a mono block, if you want to make 10,000 you make it with a two piece.

The move to the two-piece block was primarily about a better seal for the combustion gasses. Both versions were mass produced in very large quantities.

The single-piece block had the arrangement shown below for pulling the liner up to seal to the head inside face. This (predictably) gave extremely uneven
loading distribution to the gasket ring (between the blue and red parts), this meant it was unable to reliably work at high boost levels. Hence, it was
replaced by the two-piece block, which sandwiched the gasket ring between them, thus giving a very large distance between where the fastener
load is applied, and the gasket ring, which evened out the forces, and gave a much more secure gas seal.

 

[fastmongrel]

Rolls-Royce wanted to use the two piece head and block quite early on but it would have disrupted production at a time when every engine was desperately needed.

I read somewhere that changing the production lines to the two piece would have cost at least 2 months production.