7520 injector size kicking our a**

Mitch D

Member
Got a new to us head for the 7520, different casting # that says it fits 7520 (dont have # with me) and junk yard says it came from a 7520. Our old injectors have too small of threads to fit into the new head and the diesel shop says they cant just put a bigger nut on without knowing what its going on. Kind of at a loss of what to do. They said they would send a call tag and get a different head but everything else is bolted onto the tractor and don't wanna pull it again. Injectors are the same as our 4320 has size wise. Parts books don't seem to tell whats the problem either. any one else have this experience?
 
It may have been of a 7520 that had been mismatch with another head, which no one realized..there are 2 different thread sizes for injectors in early 4430's/4630's and the latter ones, so a 7520 "should" be in the family of early injectors, and I think that you can change the nuts on the 4430/4630 style injectors and be okay...but I too am confused on what you have there...could you post the casting number of the head so we can maybe sort it out for you...
 
Original head R48270
Replacement head R86702
Our tractor is a pretty early SN if the head was original, but the junkyard tractor... well who knows
 
The numbers match up AR51520 head is marked R48270 or R86702

The injectors only call for one nozzle.AR53353 with a R48696 nut..

are you sure that you don't have a bad starting thread, they can get messed up by using the nut to lift a stuck nozzle and then it puts pressure on the last thread..just a thought..
 
All of the holes have enlarged threads. Nut from a newer 466 fit perfect. Starting to wonder if JD got the wrong casting # on this one...?
 
That's what we where thinking of trying but the Bosch body is slightly larger where the nut sits making the nut loose on the original injector but going to talk to the diesel shop again and hope to come up with something
 

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