touchwood 2a Posted June 23, 2010 Share Posted June 23, 2010 Hi all, I have a question about the compression ratio of engines for military Land Rovers. I guess civil engines have ratio of series 2a / cr 7:1 , Series 3 Prefix 901 / 8:1 ratio and Series 3 prefix 904 / ratio 7:1 How is the engine FFR: series 2a/40 amp, series 2a/90 amp and series3 / 90 amp? I have a feeling that they used the same spark plugs and therefore could have all the ratio 8:1 but in the User's handbook 18358 for rover 8/9 I found 7:1 cr. Thank you very much for your answers. Jarda Quote Link to comment Share on other sites More sharing options...
Brooky Posted June 23, 2010 Share Posted June 23, 2010 Hi all,I have a question about the compression ratio of engines for military Land Rovers. I guess civil engines have ratio of series 2a / cr 7:1 , Series 3 Prefix 901 / 8:1 ratio and Series 3 prefix 904 / ratio 7:1 How is the engine FFR: series 2a/40 amp, series 2a/90 amp and series3 / 90 amp? I have a feeling that they used the same spark plugs and therefore could have all the ratio 8:1 but in the User's handbook 18358 for rover 8/9 I found 7:1 cr. Thank you very much for your answers. Jarda Have got S3 engine ex 24V FFR Lightweight Comp ratio is 8:1 Quote Link to comment Share on other sites More sharing options...
ruxy Posted June 23, 2010 Share Posted June 23, 2010 It can be difficult , the engine pre-fix determines the build but cylinder heads get changed or machined to change the CR. There are many casting numbers - in particular late 2A & S3 (S3 gets very complex for casting numbers - they may be the same as the part number at that time but often not), designates slight design changes or change of foundry (gives treaceability). Often the cylinder head casting number can identify what it was originally but this does not always follow with late S2A and S3 heads where the engines were fitted with a 36IV carburettor. ========== The "general Rules" Look at the center head bolt between the carburetor and the valve cover. The surface of the head under that bolt may look like the other head bolt mounting surfaces or it may be a raised flat surface about 2.5 cm (1 inch) wide that goes between the valve cover and the edge of the head. If the mounting surface under this head bolt looks like the surface under the other head bolts, you have an earlyish 7:1 head. If you have the raised rectangular surface look carefully to see if there is a number stamped on that surface. If there is no number or a 7 stamped there then you have a late 7:1 head. If there is an 8 stamped there (This 8 will be about 3/4" high and most often looks like two zeros that are stamped to make an 8) then you have an 8:1 head. Heads with the raised flat surface that have an 8 stamped on it are genuine 8:1 heads. However there are many copies of cylinder heads from all over the world , one of the better ones that I have seen is from Brazil - IIRC the manufacturers name is Roniceli but this is not marked. I would have to check a head - ISTR they follow the same 8 brand procedure. Some of the worst copy cylinder heads - try to copy a genuine head exactly BUT they are rough - very rough - often originating in Turkey, Iraq or India. The above does not follow for very late S3 or 90" / 110" heads - there is no 8 branded - you need to look for four very small branded numbers (approx. 3mm high) to identify the head CR and if hard seats were fitted (in the case of 90" / 110"). Quote Link to comment Share on other sites More sharing options...
touchwood 2a Posted June 23, 2010 Author Share Posted June 23, 2010 Brooky and Ruxi, thanks for the reply. I check the engine's cylinder head according to the instructions ... At the head is cast number 568750 Regads Jarda Quote Link to comment Share on other sites More sharing options...
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