I have opened several threads in the past, 1 about an airbox thump, 1 about injector knock, and 1 about a miss at idle after running at 70 for more than a couple of minutes. Installed new rv275 injectors today, all problems reported in those threads are gone. Runs smooth at idle, no vibration around 1500 rpm, no airbox thump, more power, quieter inside and out. I also noticed that it idles about 2-300 rpm lower. I think I had more than 1 weak injector. Old injectors were very carboned up, and the ones that came out of 3 and 4 cylinder, had so much carbon, I could see the 3 holes in the tip, had about 1/16 of an inch build up around them.

Ya'll gotta any ideas as to why 3 and 4 had so much build up, or is this a symptom of a weak injector?

 

Oh yea, also wanted to know if I need to worry about egt's with the 275's. My pyro is post turbo.

 

nice to see someone agrees with me on these trucks having injector problems. i have not pulled mine yet but if you'd like you could search back a couple of months on "black smoke power loss" and read awhile on all of my attemps and tries to fix my problem (which i still have).
i did learn today that if your engine gets too lean in the higher rpms that the compression can pack carbon in your injectors. sounds logical to me.

 

Let me know how your mileage does too .....

 

After posting the results of my initial drive, and 1 days worth of driving prev, I have some more results. AFter several days of driveng, the rough idle returned, and the airbox thump has somewhat returned, although not as loud. I then retighten the injector lines, this caused the rough idle to disipate some, but not all. I am thinking that the crossover tubes need replaceing. Has anybody got rid of rough idle by replaceing the crossover tubes?

Mileage is a bit better w/the 275's , maybe 1.5 mpg better.

 

I also have a engine miss,not all the time but periodicaly.Where did you guys buy your 275's and how much where they?

 

Cylinders three and four receive the coldest intake air, need to tow heavy once in awhile to heat the engine up good, helps eliminate carbon build up. Air box thump is from getting on the go peddle hard building boost and then letting up on the throttle real fast, built up boost has to go somewhere and back through the air box is the only way, it's called turbo huff, and is hard on the turbo, could break turbo shaft.

 

The airbox thump I am talking about is more noticeable at idle, and at light throttle. In fact, it is not noticeable at full throttle or when boost is over 15 psi. I have had several people listen, most say it is probably a sticky intake valve, for which a valve job is the only cure.