precom chambers

Hi i have a ht4 and in the book it calls for a 3h2209 and as far as i cross gets me to 247-3292 which goes to 1s1970. now my older book for my 7u called for 4f8517 which goes to 1s1970. I thought later engines had bigger chambers so I'm confused if it's right or not. the ht4 is a 55. and has glow plugs. my 7u is a 49 and does not. can someone point me in a good direction lol thanks.

This should help clear that up.....

thank you. ok another question that says 2h3088 ring my book says 7f8267inner 7f8268 outer. se problem with machine is getting compression in coolant but also seepage around two retainer rings. i have removed head in past put new head gasket and ferrule o rings in. still have compression problem suspecting cracked chamber. also wanting to put new fuel injector nozzles in because if it sits it leaks down smokes right off bat with fuel off. is my determining at that and also have intermittent high speed misses. idles smooth as silk.