OK so my dad semi built this motor about 10 years ago and the truck was only driven on the weekends. it sat for a few months before i started driving it and it was fine. now after it sat for another couple a months i cant seem to get it running right. the timming was off but we dont know what the cam specs are to dial it in. it will crank and idle all day long. it also will drive but it smokes a little inside and the cab and out through the exhaust. any idea what could be wrong or how i could go about fixing it. i messed with the timming some could that affect the smoke?

 

any one???

 

It sounds like an accelerator pump problem. They tend to dry out and crack if they are left to set. That doesn't address the smoke but is a place to start.

Doug

 

If it was "semi" built 10 years ago, what was done to it? Does it smoke just at start-up or all the time? Is the smoke blue, white or black?
If the smoke is getting in the cab it could be something as simple as an oil leak hitting the exhaust.
Really need more info to be able to help.

 

Having the timing too retarded will casue it to smoke like its running really rich. If you have a timing light set the timing to about 8 degrees BTDC, no factory spec will work perfectly for a modded motor. I just keep bumpimg up the advance until it pings or gets hard to start and then go back a degree or two.
-John

 

it will only start smoking when i start driving it any other time it dosent smoke at all. its white smoke. The motor was punched .30 over to smooth the cylinder walls. 400 crank and pistons were installed and it was cammed but like i said before we dont know the specs. we do know that it is much larger than stock. dad cant seem to find the paper work on the build so thats why we dont know what specs it has.

 

oh it also has a holly 2 barrel

 

White smoke indicates water vapor, sure its not blue (blue, blue-gray, gray)? Oil smoke is blue and black indicates too rich a fuel mixture.
A good tune-up wouldn't hurt. Change the oil and filter and the fuel filter. Adjust the timing like Johnboy427 suggested and go from there.
It might need just a good run to get rid of the smoke. Drive it for several miles once you get it tuned up and see what happens.

 

it might be light gray. idk il have to check this stuff out when i go home. im at college right now and can only head home on the weekends. any other ideas? worst case scenarios??? lol i know the motor is fine because its not blue smoke and its not knocking, leaking oil or anything like that.

 

White smoke worst case scenario is cracked head or block. Gray smoke is typically the trifecta of blue, black, white. So absolute worst case scenario would be cracked block, bad piston rings and a fuel leak. Do I think it's that bad...probably not, but I think a few more details would help narrow the issues down.


That being said, you mentioned the smoke being white...could be a blown head gasket, pretty easy fix, just takes a while. If it's a light blue right after start up...valve seals need replacing...again and easy job. If it's a small amount of black, the carb probably needs a rebuild due to excess sitting, so gaskets and seals dried out and cracked.

 

What do the spark plugs look like ? If it's a 500cfm 2v Holley you will never get it to not run rich, they are just too big for the 351m/400.

 

oh really? i would have thought it could handle that. well i may be looking into a new carb then. any suggestions. again im on a college budget so cheap is good.

 

Slow down ..... do not buy a carburetor just yet.

It was running fine a few months ago, now it doesn't?

It sat during that time.

Why did you mess with timing? It doesn't change sitting still.

What will make a Holley run rich suddenly is a ruptured power valve. Very common, it also has a diaphram. Enginme vacume closes it against a spring, when you step on the gas vacum drops and the power valve spring opens it and some extra fuel is allowed in through the power valve passages. You've added air, now the carb adds fuel. If the diaphram is torn, cracked, etc ... it can't pull against the spring, thuis staying iopen, thus the carb runs rich and blackish smoke results along with misserable gas mileage.

Accelerator pump adds a shot of gas when you step on it just to cover the sudden air added until the engine can pull enough venturi vac to start fuel coing through jets and power valve passages. Fuel has weight, takes a moment to get it moving.

If it has a stock Holley 2 bbl or a Holley 500 cfm 2 bbl, either one, they both use a simular, not same, diaphram accelerator pump. Look at the intake under the carb, is it wet looking? Watch closely under the left side of the float bowl (driver's side) and see if gas drips after shut off? Manually pump the throttle once while watching, does gas run out under the float bowl?

If yes, just need a new pump diaphram. The bigger 500 uses a diaphram with more volume than the 350s and such. It's not hard to replace, but best done by someone who's done it before. Holley's aren't complicated, but they have enough small parts that you can loose one and not realize it until something else is messed up.

Power Valves and Pump Diaphrams and Bowl Gaskets are available seperately at any performance shop stocking Holley parts, but you'll need the carb's "LIST # ______" It's on the air horn in front of the choke plate most likely, remove air cleaner to see it.

With a bad power valve, you'll have rich mixture and smoke and bad gas mileage.

With a bad accelerator pump, you'll have an off idle bog as you add air but there's no shot of fuel to cover the sudden addition, and you'll see gas leaking under the float bowl.

Holleys are easy to work on after you get to know them. Do not start taking them apart until you have some reference material handy, exploded drawings, etc.

White smoke as others said, coolant getting in combustion chambers, likely a head gasket.

Blue is oil smoke.

Dark gray or black is gas ... too rich.

You talk about a cam .... does the engine lope at idle? I'll bet he's got a Crane Fireball cam in it.

 

well i spoke with my father and he said he just told the guy who was rebuilding the motor to 'cam' it so who knows what we ended up with. it does lope at idle. im gonna try advancing the timming some and running her down the street and see how she acts.

 

If it smokes white on startup and its sits for awhile i would say its just moisture collecting in the exhaust from sitting.... if your oil is that creamy brown color then i would look into the head gasket cracked head or block.... and again timing just doesn't move itself from sittin more likely its a carb issue... and if kinda gray color i would say the velve seals they will become hard hard and brittle and break over time this allowing oil to get down the valves and into the cylinder causing that smoke color just happened to me mine came out in pecies... not a hard fix if you know what your doing