91 TBI engine swap

My 91 c/k 1500 4x4 came with a 305 which wore out and was replaced with a 92 350 TBI (low miler)...did not change a thing.. 305 out...350 in..done. Now it is using oil, loss of power and fuel is going down hill. I WANT to replace this engine with something in the 300hp. area if at all possible with out rebuilding this engine since they only last for about 5 yrs. if all goes well. I have being searching the web but NO one builds TBI engines except special orders ( short for $$$) wich leaves me and my TBI in a pickle. I need this truck to be dependable since work is 2,500k away. I`m sure Someone has come across this problem before and would like to know what they did and how they did it. I am handy with Duct tape and WD-40 so almost anything goes. Thanks to ANY one who can help point me in the right direction. I just lost hydro while working on this so do not know if previous thread got posted or not. Sorry!

My 91 c/k 1500 4x4 came with a 305 which wore out and was replaced with a 92 350 TBI (low miler)...did not change a thing.. 305 out...350 in..done. Now it is using oil, loss of power and fuel is going down hill. I WANT to replace this engine with something in the 300hp. area if at all possible with out rebuilding this engine since they only last for about 5 yrs. if all goes well. I have being searching the web but NO one builds TBI engines except special orders ( short for $$$) wich leaves me and my TBI in a pickle. I need this truck to be dependable since work is 2,500k away. I`m sure Someone has come across this problem before and would like to know what they did and how they did it. I am handy with Duct tape and WD-40 so almost anything goes. Thanks to ANY one who can help point me in the right direction. I just lost hydro while working on this so do not know if previous thread got posted or not. Sorry!

305 cu 4X4 is under powered for sure. 300HP V8 lots of luck finding that one.

the 350cu uses too much oil . when did this start ? how much oil does it use ? you are using 10-30wt oil ? did you replace the PCV and test that the crankcase venting is correct. also make sure your not dumping too much fuel into the intake as this will cause oil consumption and low MPG...

these 350cu engines with proper care last 200,ooomi normally.

Engine has 283000 on it. PVC system is good and I use Quaker-state 10/30. Over time oil consumption has slowly creeped up. Now it uses one l liter every 2500k like clock work and oil is changed every 5000 k. Millage is`nt bad but its not what I`m used to (about 16mph now). To date I have not rebuilt the throttle body on it but have run injector cleaner through system at least once a year (Sea Foam etc.) The truck is well maintained and is still a good daily driver for being 21 years old. I would just like it to run as good as it looks and sounds. Thanks for input as those are areas that can be easily over looked and cause problems. In my case the compression test was a dead giveaway as to how many road trips this truck has done, though they are all with in 5psi. it says its tired of this nonsense.Once again TKS for input but web crawling has turned up a 290hp with warranty that fits year and model.

One other thing to think about is that the 305 ECM may not be compatible with the 350.

1 liter of oil every 2500k is nothing.

Engine has 283000 on it. PVC system is good and I use Quaker-state 10/30. Over time oil consumption has slowly creeped up. Now it uses one l liter every 2500k like clock work and oil is changed every 5000 k. Millage is`nt bad but its not what I`m used to (about 16mph now). To date I have not rebuilt the throttle body on it but have run injector cleaner through system at least once a year (Sea Foam etc.) The truck is well maintained and is still a good daily driver for being 21 years old. I would just like it to run as good as it looks and sounds. Thanks for input as those are areas that can be easily over looked and cause problems. In my case the compression test was a dead giveaway as to how many road trips this truck has done, though they are all with in 5psi. it says its tired of this nonsense.Once again TKS for input but web crawling has turned up a 290hp with warranty that fits year and model.

with the use of non synthetic oil , I changed at 3500/4000mi. got 380,ooomi on it when I sold it 17yrs later. used 1/2 qt when sold . PASS the emission test every time with, extremely low HC.

CASTROL 10-30WT.

16 MPG is a good useage amount of fuel. sounds like its running fine.

USING 1 QT WITH THE 2500mi is not bad or will effect anything.

on the HP claims , well that is all they are. many have dyno tested these 300 hp 350 engines only to find its not so.

possible the engine is running lean. o2 sensor/fuel pressure.

make sure the engine vacuum is good no leaks cracked hoses. use a guage to check for leaks. could be why its a little low on power.

So the low miler 350 cu has how many miles on it ?????