So I have a 1977 Ford F150 with a 351M. Its never worked since we bought it a year ago. Starting to work on it again I have come up on some problems.

The truck will start but it has a poor idle and once it heats up, white smoke comes POURING out the tailpipe. I have researched and thought that it could be a head gasket problem. To be certain before I go tear my engine apart I put a white rag over the tailpipe while it was running and it came out black and smelled oily.

When I pulled out the spark plugs today I noticed that some of them had gap bridges with carbon deposits. My dad and I think that if the spark plugs aren't firing like they should it may lead to the fuel exiting the exhaust ports and hitting the hot manifold and vaporizing. Don't know if vaporized gasoline is white or if this whole thing is even possible.

Any thoughts?

 

99% of the time 'white smoke' out the tailpipe means steam. You've got coolant getting into the cylinders somewhere. It could be a bad head gasket, cracked head, or cracked block.

Blue smoke would indicate oil burning, black smoke is unburned fuel.

 

Quite often "blue" (oil) smoke is misidentified as "white" (coolant) smoke.
Here's what I would do.
First pull all of the plugs and run a compression test. Ford doesn't publish actual numbers but the high and low cylinders should be within 20% of each other (Ford says 25%). I would like to see something around 110 PSI or better.
If everything looks okay, install a new set of plugs.
Pull the valve covers and check to see if there are any valve stem seal fragments clogging the oil return passages. If you find a lot of fragments, plan on installing new ones but that could explain oil burning if the compression checked out. Install new gaskets.
Change the fuel filter but, if it's been sitting for a while, the carb probably needs to be rebuilt (the Motorcraft 2100/2150 carbs are dirt simple).
Check the cooling system for oil (a sludgy gray color) check the oil dipstick for a milky looking oil. This will help tell you if there is a blown head gasket or cracked head/block.
Seeing as you said some of the plugs had a bridged gap, I would suspect that it's blue smoke and that the engine is burning oil. Could be stem seals or worn rings or valve guides.
Let us know what you find.

 

Mike is right on! but I think in order to do a compression test correctly you first should run the engine up to normal operating temperature and then go from there. If it is a head gasket problem you will not have any trouble deciding weather or not it is there, the gauge will show the loss. So do the compression test, write down the results for each cylinder and let us know what is up.
Good luck / Uncle Louie

 

Also, for a valid compression test, remove all eight spark plugs, block the throttle wide open and be sure the battery is fully charged.
And when you pull the plugs, look for signs of moisture on the plug electrodes, another sign of blown head gasket or cracked head/block.

 

Thanks Mike,

We ran a compression check last night, we took out all the spark plugs and opened up the throttle and cylinder #1 tested at 110, #2 tested at 5, #3 tested at 125, #4 tested at 5, #5 tested at 10, #6 tested at 50, #7 tested at 60 and #8 tested at 110. I don't really know if that narrows anything down but I don't have much experience.

I don't really know what I am looking for when I pull the valve covers off, but I have a Haynes manual for my truck and I'll do an update when we figure out whats going on with that.

We have changed the filter and cleaned out the carb completely already(disassembled and rebuilt with new gaskets and seals).

I had looked inside the radiator with a flashlight and I didn't see any gray sludgy stuff that you were talking about and the dipstick didn't show milky oil.

I am only sixteen and neither my dad or I has much experience with stuff like this so I appreciate all this good knowledge.

 

Well, it looks like you either have cylinder problems or head problems.
Run the compression test again, this time put a couple of teaspoons of oil in each cylinder before the test. If the rings are the problems, then the compression should come up noticeably. If it doesn't come up, that would indicate valve problems.
If this truck has sat for any length of time, it's very possible you have valves that are "stuck" open.
The compression readings are all over the place. That wouldn't indicate head gasket problems. Usually, if you have a blown head gasket, the compression will be low on one cylinder or two adjacent cylinders, not all over the place.
When engines sit for a long time, especially if they aren't protected, the valve guides can literally rust and bond to the valve stem, seizing them in place. This means that if the engine stopped with that valve open, then it stays open and won't seal the compression.
Here's an old mechanic's trick for checking the heads for stuck valves. Remove the valve cover, then remove the rocker arms. Take a hammer and strike each valve. Do this squarely so you don't bend something. You don't have to hit real hard. What you're looking for is a different "feel" or sound. When you hit a valve that is free, you'll feel it "give" a little and it has a hollow sound. If you hit a valve that's frozen, it will feel real solid, doesn't want to give any and the sound will be very solid, not hollow.
If this is the case, the correct procedure is to pull the heads and have a valve job done. Also any stuck valves you find, check the pushrod for bends. If the valve doesn't want to shut, it doesn't want to open either.
Good luck.

BTW, welcome to FTE. Lot's of good people here.

 

Don't let that bother you! No one is born knowing all this stuff, everyone had to learn. At some point everyone is a "newbie".
You couldn't have picked a better learning platform. These trucks are simple, uncomplicated and, compared to today's new vehicles, inexpensive to repair.
Sometimes they can drive you nuts but stick with it and you can figure it out. Repair it and you'll walk away with a sense of self-accomplishment that can't be beat.
Have fun with it and don't be afraid to make a mistake. If you do, back up, fix it and learn from it.

 

Excellent advice Mike! It's great to see people ask for help and actually get it.
Great job!!

 

Thanks, I appreciate the kind words.

 

Thanks for the tips,

I ran a wet compression check and some of the cylinders improved while some stayed the same and one actually decreased(we've been having trouble with putting in the tester and the spark plug back in on that one. We think that the threads are damaged so that's not a very reliable reliable reading.)

My dad is looking for a engine hoist and stand now because we think it will just be easier to take it all out to work on it. I think were going to do a whole engine rebuild. Partially as practice so we can do the same thing on my 1987 Ford Bronco, which is my daily driver. It has an engine knock so we need to fix that too, so I'm out of a vehicle for now.

Thanks for all the tips!

 

No problem. If you have any questions or need advice, just post a question and we'll be glad to help.
Good luck.

 

A used 351M or 400 motor with acceptable compression can be found in the $350 - $500 dollar range (depending on condition) just to get you by .. Just put a $60 gasket set on it and go while you build another motor that you can take your time with .. Just make sure you get a rear sump oil pan motor if it's a 4x4 truck

 

Welcome to FTE! As other's have said, this is a great resource and a great group of guys to help share info on these trucks! Like you, I'm a newbie too when it comes to these trucks, but 16 is a very distant memory for me! Great that you and your dad have a project to work on.

I see you're in ID so I did a quick search on CL and found a Ford 400 for $250
Ford 400 engine with tranny