i have a 1978 f250 work truck that smokes like crazy when i start it up for about a minute, and when i get on the road and get heavy on the gas or when i pull my cattle trailer, im pretty sure its burning oil. im thinking i need to pull the heads off and replace those rubber valve seals right?

 

i would think its more the valve seats over valve seals. which motors your truck got again? is it smoking? have you checked the oil level?

 

2bbl 400CI yea i just changed the oil not to long ago, then i rebuilt the carb and it smokes now when i start up, but it never smoked before i rebuilt the carb

 

what color is the smoke and what kind of oil did you put in it? i know a bunch of used car lots will put synthetic oil in oil burning engines that way you cant see the smoke. the other owner may have done that to sell the truck faster. just guessing. that or you may be dumping too much fuel into the engine(if black smoke). if its blue smoke then its oil. if white coolant or moisture, and i think trans fluid burns white as well? the c6 uses a vacuum modulator so if the diaphram leaks then the engine will suck the fluid in.

 

white smoke, but it smells just like all the old junkers that drive around here lol, i put...partsmaster 20w50 in it im a cheap a$$ lol so if i use a synthetic it wont smoke??

 

i edited my post a little bit. i've used synthetic oil for a bunch of old tractors that burnt oil and they never smoked. it was still burning it, but you couldnt see the smoke. whites not oil. check the transmission fluid level and the coolant level.

 

coolants full and transmission leaks a little so i add to it every now and then

i dont understand why its about half a quart low on oil the oil pan doesnt leak

 

does it have any oil leaks at all? are you sure its white smoke? could be the rear main seal. is there oil coming out of the tranny bellhousing? you may have a couple issues here.

 

the valve covers leak a little, and idk havent looked underneath, so if it is the trans fluid burning or the coolant how do i fix that

 

depends on the issue. if its coolant then its either a cracked head or head gasket, which you'll need a new head and/or the gaskets(depending on which one). if its trans fluid then its the modulator. sounds more like coolant to me though. hard to tell without actually looking at it though.

 

what motor does it have???
does it have hardened valve seats?

my '65 used to smoke until I changed the valve guide seals, but it was black smoke, I also had hardened valve seats installed when I rebuilt the motor


maybe check the carb for proper assembly since it started smoking after the carb rebuild and it's white smoke if not maybe you blew a head gasket, check the oil for coolant and your coolant level

 

what motor does it have???

 

Way back, 1977 I believe, I bought a 1974 Ford Wagon with the fake wood grain siding. It had the 400 V8 engine with about 40k miles. I bought it from a dealer and was able to talk to the previous owner. He said he changed the oil every 3k miles but he had bought it used at 29k miles. He said the reason he traded it was the bad gas mileage.

Anyway, it started using oil and smoking on startup soon after I bought it. So, I pulled the valve covers to replace the valve seals. Sludge was very deep on the heads which told me the original owner did not change the oil at all during the first 29k miles. I went ahead and replaced the valve seals but I had also seen that the valve guides were worn severely and the new seals would not do the job. I was right. It smoked bad on startup afterwards.

My point is to check the valve guides. You can also change the valve seals without removing the heads. I bet the valve guides are worn out just like my 400 and the heads will have to be removed to replace the guides.

 

how do i replace the seals without removing the heads

 

There is an inexpensive tool that replaces the rocker arm that you can use to compress the valve springs enough to remove the valve spring keepers/retainers. You can make sure the valve stays closed while you do this with a possible two methods that I have used.
The first method is to install a fitting in the spark plug hole that connects to an air hose and use air pressure from a compressor to pressurize the cylinder you are working on. I have used this technique successfully but it doesn't work on all engines. If the valves don't seal well enough this won't work. If you do try this make sure the oil fill cap is open to relieve pressure from the base or you may blow off the oil pan.

The other method I have used many times is to turn the engine to top dead center withe the #1 piston on the compression stroke. Then the #1 piston will stop the valve when you compress the spring. Then rotate the engine 90 degrees and go to the next cylinder in the firing order.