Hello, just purchased a 1990 Silverado that has a 93 5.7 350 in it. The Guy told me that it had a fresh rebuild and that it needed some fine tuning but motor was complete. After getting it home and letting it run for a bit it seemed to smoke more and more (bluish smoke). A decent amount for sure. i changed the oil and toped off all the fluids. Still about the same.

The throttle body injector has been removed and replaced it with a 4 barrell edelbrok and i also noticed that they had a inline fuel pump. Needless to say i am concerned. The oil pressure sensor is pretty lose so going to tighten that up this weekend - i doubt that is related.

I know if i punch the motor a little it will shoot a black cloud of smoke. It Does seem to run fairly well but i will say i smell alot of gas. Any Suggestions about how to diagnose the issue - i am hoping it something little but just not sure where to start? Are there other issues besides bad rings or valves that could cause blue smoke? Thank you

 

First if you have an electric fuel pump, you'll need to put a regulator on it. How many miles on it? You might do a compression check on it. Could be valve seals.

 

if I use the stock fuel pump (sending unit in the gas tank) will i still need the regulator. Just not sure if you are stating i need the regulator because its inline of because injector was changed to the carburator? Supposedly Motor is fresh with only a couple hours of run time. Thank you

 

The fuel pressure to the carb should be around 6-8 psig. If it has a couple hours of run time, it the rings should be seated, and i'd still check compression if your blue smoke is still the issue.

 

ok, i plan on spending some time on it this weekend. I will follow up Monday. TY

 

Ok Spent some time with this truick this weekend - i think the fuel pump is ok - its a low pressure one. I do however think that i am getting to much gas? The Carburator is a 600CFM 4 barrell - is that to big of a cart for the 5.7 or possibly just need an adjustment.

I pulled the plugs and they all had alot of carbon buildup on them but they were not wet at all which hopefully is a good sign that its not a motor issue? Also i noticed the drivers side smokes considerably more than the passenger side. After taking truck about a 15 mile ride - the passenger side was only smoking a little bit but the driver side exhaust was smoking quite a bit. alot of carbon buildup on the inside of the exhaust as well. Again hoping this is a fuel issue and not motor. The smoke defnitely seems to be on the blue side though.

Something is also draining my battery.

 

Carb is fine for your size. I'd first look at the choke make sure it is opening, that could cause your rich mixture.

 

I think you have too much fuel pump pressure. Fuel injectors need more pressure then carbs. Carb pressure should be 6-8 psi if your pumping to much gas it could fill a cylinder. Then you get hydra-lock & could bend a rod creating a knock. The smoke could be burning fuel forced thru exhaust valve into exhaust system. Fuel pressure regulator would solve problem. Put it as close to the carb as possible.