The V8 Owners Forum -

what do the colour codes relate to on new blocks? ive seen red and blue but dont know what this refers to, if anything?? Im sure ive read something about it somewhere.

You need to be careful that you are looking at the right blob of paint when using the colour codes. The one to look for is in the valley area of the block and can only been seen on a bare block, or at least with the valley gasket removed.

Basically the colour relates to the thickness of the aluminum between the cylinder liners, red being the best, i.e thickest (They were measured using ultra sonic waves).

I think the next best was blue then yellow but I'm not sure about the last two colours. (I've lent my Des Hammill book to a mate!)

All this was done by Rover (and contracted casters) because of the liner dropping, cracked block issues that some engines suffered by being run too lean and too hot by Rover in order to get a 50/60's design through 90's emissions laws.

Pete

EDIT....Just got my book back, I got the yellow and blue the wrong way round, blue has the least ali between the liners.

The daubs of paint denoting wall thickness between adjacent liners is applied within the lifter gallery area.

Red denotes that the thickness of the metal meets the required specification.

Yellow is next in line. Only 4.6 litre engines were made using red, and when unavailable, yellow.

Blue denotes the thinnest. Only 4.0 litre engines (made by Rover) were made using blue, and if available yellow would also be used.

Paint daubs elsewhere on the block are not related to wall thickness.

Ron.

Very interesting, and thanks for the info. However ive just bought a brand-spanking block with a blob of red paint in the lifter gallery but it aint a 4.6 -its a 3.9 / 4.2 non cross-bolt type.