Thanks Ed for giving us the info on the counterbored nozzles.I probably have the service bulletin on it some place around here & I was pretty sure it had to be a change inside the nozzle where it wasn,t showing.The later ones as I mentioned before were not flat on the end tip but was step cut with the thicker part toward the center & the hole & the under cut on the outside diameter of the tip.Working on engines you didn,t really give it a thought as to why or how they were called counterbored nozzles as you just installed the correct part it called for.As for the nozzles the part number for a nozzle service group is different than the number on the body of the nozzle as the seals were part of the valve service group so gave the group a different part number.

Hi SJ,
glad to help, and spread the little known inner details, where possible, of some of the updates incorperated into new parts, may help someone who is confused over different nozzle types in the same engine or engine family etc.
You are 100% correct, when you're on the shop floor with the pressure on you don't always get the time to muse over the whys and wherefores of any given update until you get a chance, (usually in your own time) to catch up on the relevant Service Article. Because of my time in the Fuel Pump Room this info was about and used periodically, we had this sort of data stored in an "Injector Folder".
Regards
Eddie B.

Thanks for the info edb,
All I remember seeing is this type but then I may not have been paying attention. Is this considered to be counterbored???

Hi OM,
the unit you have pictured is a NON-counterbored nozzle, ie, the early type.
The later ones are bored larger inside from the needle valve seat to just short of the outlet when the bore reduces to the orifice outlet size for possibly 0.060"? of orifice length.
Hope this helps, must make time to learn how to post these P/B's, S/M's etc., would satisfy the old picture is worth a thousand words statement. Have tried unsuccesfully so far, need to destroy more brain cells to get there, haven't mastered the scanner yet!, let alone posting. I'm so computer savvy that I crashed CofOz's computer once trying to get service data!. I.T. Dept changed some of the key board key functions but did'nt tell Serv. Dept. ahh all good fun in the sun as they say,
Cheers for now
Eddie B.

Thanks edb,
Found it, not a very good picture but enough to satisfy my curiosity:)

OM that is a plain enough picture & gives me the answer of what the counterbored ones are.Working on engines all those years I never really give it a thought what the difference was but now we all know who has visited this site.One other thing is it takes .115 more rack travel & 30 more RPMs to arrive at the same HP on this 3U 112 grader engine than with the older style nozzle with same gov. spring & camshaft in the inj. housing.

Hi SJ,
Been meaning to ask you about that. The rack setting books I have (3 of them) and the fuel injection testing manuals I have (two of them) make no mention of the two different nozzles (unless I missed something). Where are you seeing this info??? My oldest rack book is 1961 so maybe it was before that. The only reference I see for the different hp and rack settings on the 3U (ref # 12) was about cam ground pistons.

The Cat rack setting book I have was printed 8/53 & the form # is 30782-1 & it lists both nozzles & settings for both for each engine.I,m kind of thinking maybe all nozzles in the little later engines like your book lists are all the counterbored nozzles but no proof of it.I don,t have any NPR book to check how long this nozzle was used but the book shows that the D2, D4 & D6, & in other equip where the D311, & D315, & D318s are used all take the same nozzle number 9F4113 counterbored nozzle.Over the years nozzle numbers kept changing so it,s hard to track each one unless you have a parts book for the particular engine your working with. I should have stated that the part number in the parts book will be different than the 5F4113 is as the parts book is a valve service group & it includes the seals for installing the nozzle so Cat puts a different number on it so you know it has the seals with it.

Is it OK to run the engine with both types of nozzles in it?

I noticed in the photos that at the upper part of both nozzle bodies, there is a differece between the two, where the fuel enters the body. The later type looks like it's counterbored there also, is that correct?