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.

The heads on the D318 engines are interchangeable of the early to late. So I think the other engines would be the same. So machine serial numbers may not get you the right pre chambers.

The seal between the chamber and the head due go bad. With luck a new seal washer will fix it. I have used a generic copper washer from McMaster-Carr. A pure copper washer crushes more than the copper coated steel washer Cat is now selling. With the angle the chamber sits at most engine rebuilders do not have tooling to dress the seats. But a member here had a thread on building your own tooling to dress them. But good luck using search to find something buried here many years ago.

In general Cat 311, 315, 318 heads are very tuff and do not crack like the competitors from back in the day. So if there is combustion gases escaping the pre combustion chambers is the first place to look. The chambers themselves can rust hole as well as the seats leaking. Twenty years ago my machinist guy was very impressed with the quality of some after market pre combustion chambers, don't if the quality has been maintained.

back in the day we had a few pre-combs of the usual thread sizes that I am sure the machine shop bored out the pre-comb blast hole to suit a guide rod from the valve seat grinding tool set.

The pre-comb was screwed into the head from the combustion side --not bottomed but loose in the head threads so as to maintain alignment as well as could be--yep, not the best but it sure worked-- a valve seat grinding stone of appropriate size was used --flat side down in the pre-chamber hole in the head and the minimum amount was ground down from the pre-comb washer seat to get a good seat for the pre-comb washers. Some operator diligence got 'er done.

Your experience may vary.

Cheers,

Eddie B.

so first chamber cam out turning fuel injector nut. second has fought for the turn and a half i turned it till my wrench slipped. Is it normal for them to be that tight getting out? first was way under torqued. thanks

Am I understanding correctly that it came out without using the special splined tool ? That is way to loose.

yes, it came out just by turning the injector retainer nut. once chamber was out had to put a pipe wrench on it and hit nut with impact to break loose. the other chamber is being a bear it takes a cheater pipe and a lot of force to turn but is turning. is this normal I'm worried it was cross threaded and the threads will be toast once out? the other once broke loose with half inch breaker bar ratchet came right out.