need turbo help on 1855

my 1855 with completely overhauled engine , injection pump , injectors , complete machine work ect.. will not make over 4 psi of boost & i have to overload it to get that , anyway it seems like the turbo is the problem it was rebuilt by turbo supply , which is on the internet , it has all the original housing on it, my question it do they make different pitch turbine & compressor wheels for the Garret turbos on an 1855 310 engine? this whole turbo ordeal is nuts , the first time they sent the wrong one , 2nd time sent one that was to big , looked like one for a perkins maybe , so then sent them mine to rebuild but did i get the right pitch wheels put in there? housings are mine because i marked them & didnt tell them i did so , if the turbo is the problem it has to be pitch of wheels they replaced. of course the company just gives me the run around ,i dont think they even know how an engine works let alone help with tech. issues, just parts changers that slap things together. i have nothing nice to say about them & others should beware of turbo supply, which by the way my local pump shop set this turbo to them not me , of course they want to pass the buck now too. anyway ive been throw this engine with a fine tooth comb , that turbo is the only thing causing low boost & excess black smoke. can anyone help with this turbo boost issue

I'm not trying to offend anyone, but I've seen "rebuilt" engines with shop rags stuffed in an opening in the intake manifold or somewhere else in the path of air intake. Good intentions of keeping dirt out, just forgot they were in there.

ya me too , but there no rags in this one

Garret? They came with an Air Research TO4. Is the charger you have too big for that engine? They need to be properly sized and the TO4 was adequate for a 310. Not saying there isn't a Garret that would work but I would make sure.

the Garret / airsearch TO4 is whats on this engine , it is the original turbo , had it rebuilt during overhaul & now it wont boost over 4 psi ,with no problem found with engine its self , runs & starts like a top but rolls black smoke under any kind of load lite or heavy, question remains is it possible the rebuild shop put the wrong turbine or compressor wheels in this turbo , do they make different pitch wheels for this turbo or is there just a standard of them?

The following is not specific to the turbo you have, but general info gathered from ~30 years of owning/building turbocharged cars.....

Most turbo manufacturers have different turbine and compressor wheel styles and blade designs to fit a housing. Biggest differences I've seen are blade count, staggered blades, and clip angles. These have more effect on pressure/flow curve than peak boost pressure.

Every turbo that I've dealt with has a wastegate. This is a device that regulates maximum boost pressure. Essentially it is a pressure controlled bypass valve that allows some of the exhaust gas to bypass the turbo when the design boost pressure is reached. Does your turbo have a wastegate? If so, it may not be connected properly or maybe the incorrect one for the tractor.

The wastegate actuator is controlled by a boost control valve. There are several styles, but for simplicity, lets just say it is a pressure regulator. When the design manifold pressure is reached the boost control valve opens and allows manifold pressure to the wastegate actuator. The actuator opens and begins to bypass exhaust around the turbo which limits its ability to raise more pressure.

Sorry for the long-winded response!

Make sure you don't have any boost leaks either. I would pressure test from the turbo elbow into the intake just to be certain there are no leaks. As other guys said there are many differently designed hot and cold wheels for turbos making a big difference in boost. I'm going thru the same deal with another tractor that we replaced the turbo on.

Can you find the A/R number stamped on the exhaust housing? The turbo I have on my pulling tractor was changed from a P.58 to a P.69 to slow it down to lower the boost pressure some. You may need to replace it wit a smaller number so it will spool up at a lower engine speed.

I just got done restoring a 1855, when we painted the turbo the paint shop took off the intake housing to paint it red, but rest of it was to be black. When I got it back there was a ring that goes in between the housing and the backing plate. I installed it backwards and it ran terrible, it was actually pulling vaccum in the intake manifold. I finally took the intake housing off and flipped that ring around and it runs like a top. U could check it, but I don't remember which way it is now.

TO4 have 3 different turbine wheel size holes.then their are A/R ratio stamped on the the exhaust housing more likely 100 but can get faster ones to turn the turbine faster.Then we go to the air side same thing their bigger wheels more air and boost.On mine I steeped up the the wheel size and housing They did change the air housing to the newer one.The heads on the 310 flow really well so you are getting good air flow with less boost.

I was thinking of a Holset