I,m sure there has been engines run with both types in it but my guess is there could be a little difference in power & also there could be a little smoke change in the exhaust as the counterbored engines call for more rack travel to arrive at the same HP so if the regular nozzles were in an engine setup for counterbored then you might get the little more smoke from the cylinders with the older nozzles in it but I have no proof but just guessing.It, been too many years to remember if an engine I worked on had a mixed set in it & how it responded.

Hi Team,
yes SJ & OM the S/M May 31 1951 does cover what you have reasoned. The counterbored nozzles deliver less fuel for a given rack setting. Individual replacements of the C/B nozzles can be made, but if more than half of the nozzles are to be replaced then it is recommended that all the nozzles should be replaced for a smoother running engine.
It also recommends that if more than half of the nozzles are to be replaced then the rack setting should be opened up to recover the MAXIMUM Available horsepower, as some track-type tractors, road graders & electric sets seldom run at Maximum output, the counterbored valves in these engines will not cause a noticeable effect. Engines that run at full rack setting ( torque spring deflected ) will require an increase in rack setting when more than half the valves are replaced. Refere to the new rack setting charts in the Servicemans Reference Book (?) Do not recall seeing these in the SRB's. It goes on to say that the small increase in RS will slightly increase the High Idle speed, but is of little consequence.

The new nozzles became effective with the following S/No's

D2 4U4172 D311 Ind 7S6874 D311 Elect Set 4V5788 D311 Mar 9S100
D2 5U7621

D4 6U6371 D315 Ind 9S7733 D315 Mar 5V211 D315 Elect Set4V471
D4 7U13054

D6 8U4512 D318 Ind 5V9971 D318 Mar 6V301 D318 Elect Set 3V5457
D6 9U7608

DW10 1V1850 No 12 MG 8T7607 No 112 MG 3U2833 No 212 MG 9T2237

For 1500 RPM Ind engines a change of gov. spring is given:- D311 5F1940, & both D315 & D318 5F1941. There are other changes to the torque springs in DW10 gov.
When I get up to speed on scanning etc. I will post this S/M article in full, unless some one beats me to it.
Regards
Eddie B.

This is all going to get very confusing. The later rack setting books make no mention of nozzle options. edb, at what edition year would the rack setting books all revert to the later 6H3364 nozzle part number for the 4 & 4-1/2 in. bore engines (current available) with the correct rack settings.

Hi OM,
sorry can't presently answer that one.
I would assume that an update to the then current R.S. book in the form of an insert would have been issued. My R.S. book page for , as an example D2 4U1--4U5009 issue date 12-56 gives R.S. at + 0.285", D4 6U1--6U10321 issue date 8-61 is +0.200", what they were earlier I cannot say. So sometime between May 31 1951 and Dec 1956 is as close as I can tie it down with the info at hand, this does'nt help really, but I will search further and see what I can find.
I only recall seeing 2 copper wrapped nozzles in my 43 years at the dealer and these were in the last 5 or 6 years!. We thought they were after market until we checked the literature being discussed here, because they had a Cat P/No.
Just looked at a S/M March 28 1952 article on Counterbored Nozzles for 5 1/8" Bore Engines, it says:- " Rack settings for 5 1/8" bore Diesel engines using either straight or counterbored nozzles appear in the Servicemans Reference Book, ""Caterpillar Fuel Injection Pump Housings"" which will be issued shortly".
Looked at mine earlier, issue date 07-56 Form No 7272E does'nt give any rack settings at all for any engine, only proceedure, also proceedure for lifter settings and setting dimensions. I now can only assume that the "Rack Setting Book" was introduced between these dates, March 52--July 56.
Cheers for now
Eddie B.

My old book dated 8/53 has the insert pages pasted in & it says the Counterbored are the same as yours EDB & the regular nozzles are .215 rack setting for the D2 & the D4 is .115 for regular nozzles.There is no date for it but the D2 goes up to 5U9813 & the D4 goes up to 7U15661 for the settings listed.

This is getting worse:rolleyes:
I have the 7272E manual. Pages 36-39 give the rack settings but it's all done with fixtures and spacers. No mention of different nozzles there. Also no mention of optional nozzles in the Form 11238-3 "Diesel Fuel Injection Test Apparatus".
The picture of the counterboard nozzle came from Form FEO11238-07 (1971)
"Special instructions on using the Cat Diesel Fuel Injection Test Apparatus" but there is no detail other than checking the screen:confused:
Interesting that there were at least three??? maybe more systems of Cat rack setting guages by 1971. Fixtures & spacers, the 3H1690 dial caliper, then the various dial indicator types which could still be used on the older Cats.

Hi again OM,
Page 44 gives a NOTE:- "Rack settings are given in another publication of the Service Department, Caterpillar Tractor Co., Peoria Illinois"
pages 36-43, I feel are only giving the method of rack setting and not actual setting figures.
I did my first stint in the Fuel Pump Room as a 3rd year Apprentice in 1964-5.

The illustration on Page 37, FIP Housings, shows setting a forged body pump and we can see that the rack setting would be measured in ONE INCH PLUS and, possibly, not Less than One Inch, as given in our RS books. It seems to me studying pages 38-39 they are indicating settings of over 1 1/4" and not much less than 1 1/4". A quick flick through the RS Chart Book shows ALL Rack Settings to be well under 1" for all engines from back as far as the D3400 onwards!
We need to establish when the 3H1690 and 8M0530 guages were introduced and this may tell us when the settings changed. The change possibly incorperated the required new settings for the Counterbored Nozzles. PHEW!
Look out it's kinda getting out of control.
I feel the settings given in OUR Rack Setting Books, mine issued:- 3-66, are achieved using the 8M0530 Thimble Micrometer Guage and the 3H1690 Vernier, and not the old gear shown in the Fuel Injection Pump Housings book Form No 7272E.
I'm sure I had no trouble setting rack settings and obtaining HP on the Dyno using this RS book and the the Thimble mic. on compact pumps and the Vernier on forged body pumps.
The equipment shown on pages 36-42 is still about the Dealer but I have never used it.
I did use the 5 1/8" Bore gear on my D337, 8W S/No., (roots supercharged) scraper converted to industrial engine when I re-rated it, after rebuilding 2 blown up units into 1 goer.
The straight pipe music from one of these is something else, KoO eat your heart out Mate, these things are definately deafening material.
I did run this engine on a water pump at our local Steam Club Rallies, incidently run on the lake at Swishy's Dads property at the time, current Swishy's Place.
Any enough of killing brain cells for tonight, getting the LOOK from She Who Must Be Obeyed.
Cheers
Eddie B.

Hi edb,
After closer reading I would agree (learning here) that the dimensions given in the 7272E are for various spacers and gages used to set the rack but the actual rack setting dimensions are missing:confused:

You mention an 8M1690 gage, I only know of the 3H1690 vernier caliper. Is there another?
I have a 3H1690 gage complete with original wood box and instructions with sheet dated 11-55. It is also listed in my 8th Edition "Cat Service Tools" dated 1-55 so I'd guess that was about the time it arrived.

The 8M0530 micrometer guage came later with the change in fuel injection pumps about 1960 but I suspect the current injector nozzle (counterbored) was the standard by then.

Never could find what the 1M6953 gauge looked like.

Glad we have someone on board from the "pump room". I have found it very difficult to get information on the early Cat injection systems. Must have been a closely guarded secret:D

This gauge can only be used on the injection housings that are the big housings like the older D2-4-6-7-8-9 & the later gauge has to be used on the compact fuel housings starting with the later D311 & D330 & D333 etc. & looks like part of a micrometer & bolts in the front of these housings.

Hi SJ,
Just re-read some previous posts and realized your rack setting manual was 1953 and had settings for both nozzles. Were the settings achieved with the 3H1690 gage?? And I guess the quest is to determine when that gage became available. The thinking being the gage and the counterbored nozzle arrived on the scene at about the same time, maybe corresponding to the 1951 service letter that edb mentions.

Checked on the serial numbers of the units with the nozzle changes and they are for 1951 models.
Still searching for the origin of the 3H1690 gage.