my timing chain has slipped a few teeth and the truck is no longer starting it’s a 1981 f150 351w, is it as simple as replacing the timing chain if so should I go with a double roller? Also I plan to replace the water pump while I’m at it. How can I tell if I bent any valves?

 

First you posted this in the FAQ area and not the main area for others to see it.


Yes it is just that simple. just replace the chain & gears.
Yes on the double roller.
Good plan on the water pump as it is off anyway.
Unless you were spinning the crap out of the motor, really high RPM, I don't think you have to worry about bent valves
To tell you can pull the heads pull the valves from the heads and check each one.
or
Put the new chain/gears in it and start it up. If any are bent you will have I miss/no compression in that hole(s).
or
back off all the rockers to the valves are closed and put air in thru the plug holes and listen at carb & tail pipe for air coming out.


Again I would not worry about bent valve as I have never heard of this unless turning vary high RPM.
Dave ----

 

Compression and/or leakdown test.

 

 

Again he would need to back off all rockers or replace the chain assy. And at that point might just try and run it.

I did not know it made a difference?
Guess you would have to pull it apart to see is the only way I can think of.
Dave - - - -

 

I wouldn't bother buying parts and wasting time changing a chain and buttoning it up unless I was sure the rest was in good condition. You can make an adapter to put air in a cylinder out of an old spark plug and an air tool fitting, been there done that. Real quick and easy to see if you've got leaky valves, there will be air coming out the intake or exhaust. At that point you'll know at minimum if the heads have to come off.

 

When did old v8's become interference motors if the chain went south?
Unless he was spinning this thing to the moon valves did not kiss the pistons.
Dave - - - -

 

Why do you think the timing chain slipped?

 

I guess that should have been the first question asked.
Did it stop running when driving down the road? That could be something else.
Does it turn over really fast when trying to start it?
Then yes it could be the chain.
Dave - - - -

 

In my experience a engine where the timing chain has jumped will crank very unevenly. You will definitely notice the difference, it may crank fast and then slow almost to a stop and then turn fast again.

I have never had a stock older type engine like these, bend any valves when the chain jumped. They are not interference engines like some of the imports are.

The are several things that can go wrong doing this job and can be very aggravating for a experienced mechanic, and a show stopper for a beginner;

1. Stuck bolts. There must be 4 or 5 different length bolts that hold the front timing cover on, so keep track where they go. The the timing cover is aluminum, so the bolts over time can corrode and get stuck in the aluminum. It can be a battle. They even get stuck in the alternator housing. If you have to saw the cover off, you can buy a new one at the store(last time I checked). Check for corrosion at the water ports, if it's really bad you may need a new cover anyway.

2. Getting the cover off with the oil pan still tight. I have never been able to do it, I always have had to loosen the oil pan and let it drop a little bit so I can get the cover off. You have to take the front two bolts completely out, and a timing cover gasket kit will have two little short pieces of oil pan gasket that you can glue and splice back in place.

3. This is not difficult, but you will need to go buy a balancer puller from the store to pull the harmonic balancer off. There is a very large bolt in the middle that has to come out, and then you thread small bolts into the balancer after you take the lower pulley off and pull the balancer off. Once you get the balancer off, check the surface where the front seal runs. If it has a groove, you will need to buy a speedi-sleeve to repair that area so the new seal will not leak. It's very common, some kits even come with the speedi-sleeve.

If you have a carb with a mechanical fuel pump, I would think you would have the two piece eccentric.

 

I've been wrenching most of my 64 years and can't remember a timing chain just "slipping" a few notches. When they fail a whole gear is stripped off. Usually the ones with the fiber cam gear.
I did have a 70 Impala with 200,000 miles loose the timing chain once and bend a whole bunch of valves and pushrods. I was barely idling along about 20 when it happened. Never knew a 350 chevy would do that

 

I had a 73 Blazer with a 350 truck motor and it lost the chain doing about 30 mph and a buddy in a chevy wagon lose a chain when pulling a car trailer doing 60-65 mph and nether bent valves.
You must of had that 1 off 350 everyone talks about
Dave ----

 

Most of the v8's in the 70's and 80's, Gm and Fords, used a plastic coated cam sprocket for the timing set. As they get old the plastic cracks and falls off, usually partially clogging the oil pump pickup. Then you are left with the bare aluminum of the sprocket now that the plastic has fallen off, and it doesn't take long for the chain to wear the aluminum down enough to where it finally jumps a few teeth and then the engine will not run.

 

id been having issues with timing, reset it and it ran fine for awhile. I was seafoming the truck revved it a bit when it just cut out then was only cranking again just like it was before.

 

These are not interference engines stock, so no worries about bashing valves in to the pistons.

Double roller is the way to go. But don't buy a cheap one as they are no better than than the flat link that was in it.

These flat link chains can stretch quite bit over time and can jump a tooth or 2. Usually you will initially get a one tooth jump usually at engine shut off or just after start up. That can be corrected with a timing adjustment and the engine still run fine.

The next time it jumps you likly will be a few teeth jump.

The cam gears in this era had nylon teeth to reduce engine noise. They do in time age and can break off or they wear badly. If large chunks of teeth are missing they will be in the pan. You can try to flush them out of the pan when the timing cover is off and the pan plug pulled. If not able to flush them out you should drop the pan and clean it and pick up screen.

Use a felpro timing set it comes with a speedy sleeve (they used to anyway)

Your fuel pump eccentric can be either single or multi piece in this era it should be multi piece.


If your truck was running then quit and you had to reset the timing to get it running it is a pretty safe bet the chain jumped.

I've never had a stock Ford nylon timing gear chain exceed 120K miles personally , in an OHV engine. All have jumped before then.