1992 HMC with 12V Cummins

Thanks again, Scott, you've given me a wealth of information.

Changing injectors does not disturb the injector pump but it's probably a good idea to check the timing since we don't know what a previous owner may have done. Wish I could help you with the data plate but any highly experienced shop should be able to do it. There is no adjustment for the injectors themselves.

OTOH, low boost doesn't mean bad turbo (it's easy to inspect a turbo BTW). There are a dozen places where you can have a boost leak (hoses, clamps, intake, intercooler, etc.) I just replaced a boost hose on my own rig that leaked like a piece of Swiss cheese. It looked fine outwardly.
You will not get enough healthy boost out of your stock turbo to support those injectors. The air would be too hot and you'd have to over drive that turbo real bad.
If you do get a new turbo, get one with a wastegate (See Fastbacks post) but with those sticks, it will only help slightly. It would be a big improvement with 40 HP sticks.

Your worst enemy is those injectors!

With the right combination of parts, that eng is an amazing performer!

Thank you all for the information and advice. If there is anyone with a Hawkins Motor Coach similar to mine I would like to know what the factory settings are for injectors and fuel pump settings. As of now I'm leaning toward replacing the turbo since I have low boost and run an oil analysis to check for fuel dilution which should tell me whether or not to change injectors. If I replace the injectors the injector pump will need to be retimed thus the reason for looking for factory specs.

I daily drive a '92 Dodge 12 Valve. Don't get greedy with the sticks or you'll start breaking other things. Sound like the PO went beyond reasonable with 300s. I have some DAP 40 Horse in mine and with a HE351CW off a new Cummins it is fun to drive. Pulling our 8k loaded Toy Hauler up most hills in direct drive see around 1,100F on the pyro and 55-60 on the spedo.

Try calling The Hungry Diesel and talk to Eric. He lives and breaths 12 Valves.

The 92 would have been 160 HP and it's a wonderful eng.
300 HP sticks are going to have lots of smoke and heat. A turbo upgrade would help but those injectors are problematic in a heavy vehicle.

If it were mine, I would replace them again with 40~50 HP sticks. They aren't all that expensive and the job is easy. I have replaced a set in that eng in about 45 minutes.
Then if you want to upgrade further, replace the turbo's housing with a waste gated 16 CM unit and it will act like a totally different animal (quicker spool) and have less smoke.

I had a 1995 Safari with the 12 valve 5.9 rated at 230hp. Some of the earlier ones were rated at 210hp. Good engines, pulled very well for their rating.

Sorry, can't help with more info.

google is your friend. Maybe Wolfe will stop by later to add or modify this.

https://www.engine-specs.net/cummins/6bt.html