Well I am about two weeks away from heading across the country back home.

I probably should have done this earlier, but I can't imagine that anything that I do is going to take too long.

First of all, I can't stand this motor. I have long thought of just dropping in a Windsor and not worrying about this M block anymore.

Starting off, its got 105,300 miles on the clock. Since I got the truck about 1 year ago, I have replaced the plugs and wires, and ignition coil, its got a 160 thermostat, and a new 3 row radiator. I just rebuilt the Motorcraft 2150 carb, and it ran really well and got decent mileage for a while. Now that it is cold, it still starts right away, and the idle is really high (guesstimating ~1300 RPM). It runs cool all the time but in the Normal range which is good enough for me.

It doesn't burn any oil, but has a terrible exhaust leak, I can't fix that because I can't break a bolt off in the head, I have no way to fix that here at school.

The timing chain is stock, and I have no idea how worn it is, I can't measure free play in it.

It has pretty decent oil pressure since I run Wix filters and Valvoline MaxLife 10-30W with a 1/2 can of seafoam in the case. However it has a progessively worsening upper engine rattle that most resembles a diesel engine knock, it only is apparent when under acceleration past 1/2 throttle and when climbing anything that looks like a hill.

All of my emissions equipment is connected and working per the testing procedures in the Chilton's guide.

I have a very present hesitation that sometimes stalls the motor when driving around town. I have the air screws in the carb turned to 1-3/4 L and 2 R. Anything below that will result in stalling at idle.

Thats all I can think of for now.

 

Make sure the choke is releasing the fast idle cam when the engine is warmed up. If not, you'll have to adjust the fast idle cam position. Warm up the engine first, or rotate the choke thermostat to open the choke all the way, then use the screw just behind the choke thermostat housing on top of the choke linkage to adjust the fast idle cam so that the fast idle speed adjusting screw on the throttle shaft doesn't engage the cam.

If the fast idle cam is adjusted correctly, try setting the idle mixture needles open a little more (3 turns on both), and then reset the curb idle speed with the engine warmed up.

The rattle you're referring to is pinging. Try reducing the ignition vacuum advance sensitivity. If you turn it down all the way and it still pings under load, you'll have to retard the ignition base timing. What is the base timing now?

Remember, if you adjust ignition base timing, you have to reset the idle speed.

One more thing, that 160-degree thermostat is literally killing your engine. In cold weather, it won't allow the engine to get up to it's "normal" operating temp, so the engine is running without correct internal clearances. Cylinder wear is accelerated dramatically by running the engine too cool. Even though there is a minor performance benefit, I would never run anything cooler than 180 degrees if I wanted the engine to last more than a few races.

Also, that 160-degree thermostat will aggravate any cold weather running problems you might have.

Give a little more info about exactly when the hesitation occurs.

 

You can check your timing chain by pulling the dist cap, grab the fan and turn it back and forth. Provided that its not slipping on the pulleys you will get an idea of how much play you have by watching how long it takes the rotor to start moving.
Your diesel a rattle or an actual knock? If it's a rattle like a cummins then it's probably your valves, get a vac gauge or test light and check your timing. You'll probably find that is the the likely cause of your hesitation.
I take it your exhaust gasket is shot?? I know it's not a great fix, but get some jb weld or some of that "steel putty". Yeah yeah I know that stuff is supose to be forever but on an exhaust manifold it's not. I redo the exhaust manifolds on my 75 Ford 800 Dump every inspection to cover the leaks. Only because like you I don't want to drill and tap the heads. The weld or putty should hold a few miles, atleast till you find a good radio station.
The tune up and carb rebuild you did is normal for an engine of that mileage, esp depending on how it was taken care of before you got it. The 351m isn't a bad motor...would just be better if it were a 400

 

for God's sake son, remove all the emission junk from that poor old motor, it will really wake it up.

with 105,000 miles, how can you complain ?? I'll admit, the 351M is a lot of weight to get only 350 cubic inches.

you need a 400 !!

ps- remove the EGR, run a straight vacuum advance to the distributor, make sure the choke opens all the way after warmup, if it's not then turn the adjustment until it does.

vacuum time the motor, by this I mean, put a vacuum gauge on the intake manifold, disconnect the vacuum advance. turn the distributor until you get maximum reading in inches HG, then back the distributor off until that reading drops 3". You will be very close to optimum timing for a worn motor, based on intake signal, not stretched chain and retarded cam timing. I've had guys follow this advice and turn slugs into tire smokers, not kidding.

then reinstall vacuum advance.

 

Ok well, I am not planning on changing to a 400 by any means, and I can't feasibly tear off all of my emmisions equipment, I am not trying to make a performance motor, I just want to get home.

I am pretty sure the gasket is shot, there aren't any cracks on the top of the manifold, and I can't see underneath. I got some new Fel-Pro gaskets (the $30 ones) and I got most of the bolts off of the manifold except that four didn't want to come off and I can't break them so I put some anti-seize on and reinstalled the bolts.

I am pretty sure the rattling I hear is from the worn valves from the years of **** poor oil pressure. I heard some where that the 335 oiling pressure problem can cause accelerated wear on the valve train.

I don't have a timing light or a vac guage.

I get hesitation whenever I need the motor, If I need to pull something or if I have a load or when I really gotta move. I don't know if thats descriptive enough, I get hesitation that almost stalls the motor when I accelerate at all, about 10% of the time it stalls. If I hold the pedal to the floor it won't stall.

I know where this motor is going when I get home.

 

OK MY ANSWERS IN BOLD PRINT:

[QUOTE]Originally posted by mattsbox99
Ok well, I am not planning on changing to a 400 by any means, and I can't feasibly tear off all of my emmisions equipment, I am not trying to make a performance motor, I just want to get home.
THE EMISSION REMOVAL IS NOT TO MAKE A PERFORMANCE MOTOR, JUST TO MAKE YOUR MOTOR RUN THE BEST IS CAN, WITH WHAT YOU HAVE.

I am pretty sure the gasket is shot, there aren't any cracks on the top of the manifold, and I can't see underneath. I got some new Fel-Pro gaskets (the $30 ones) and I got most of the bolts off of the manifold except that four didn't want to come off and I can't break them so I put some anti-seize on and reinstalled the bolts.
USE A 6-POINT SOCKET AND BREAKER BAR, 1/2" DRIVE, THEY WILL COME LOOSE. PERHAPS USE A SMALL PIPE OR HYDRAULIC JACK HANDLE FOR LEVERAGE

I am pretty sure the rattling I hear is from the worn valves from the years of **** poor oil pressure. I heard some where that the 335 oiling pressure problem can cause accelerated wear on the valve train.
LOW OIL PRESSURE DOES NOT WEAR VALVES ! MOST LIKELY YOU HEAR SPARK KNOCK, MAIN/ROD BEARING NOISE, OR LIFTER/ROCKER ARMS FROM A WORN CAM/LIFTERS/ROCKERS, OR CUZ OF LOW OIL PRESSURE. YOU MAY BE JUST NOT OILING THE ENGINE HARDLY AT ALL ANYMORE !

I get hesitation whenever I need the motor, If I need to pull something or if I have a load or when I really gotta move. I don't know if thats descriptive enough, I get hesitation that almost stalls the motor when I accelerate at all, about 10% of the time it stalls. If I hold the pedal to the floor it won't stall.
THAT CAN BE A MULTITUDE OF THINGS, FROM PLUGS, WIRES, CARBURETOR ACCELERATOR PUMP, FUEL PRESSURE, SPARK CURVE, YOU NAME IT. THERE'S NO WAY TO TELL ON A NET THREAD LIKE THIS, WITHOUT ACTUALLY LOOKING AT THE ENGINE. IT SOUNDS LIKE YOU ARE A BIT OVER YOUR HEAD, TAKE THE TRUCK TO A GOOD SHOP AND HAVE THEM LOOK IT OVER.

I know where this motor is going when I get home. [
/QUOTE]
LOL- IF THEY WEAR OUT, YOU REBUILD THEM, NOT THROW THEM AWAY. IF YOU CHANGE TO ANOTHER MOTOR, MOST LIKELY YOUR MOTOR MOUNTS AND EXHAUST WILL NOT FIT- ALONG WITH A FEW OTHER THINGS. AND IF SMALL BLOCK, THE TRANS WONT' BOLT UP. IF YOU ARE HAVING DIFFICULTY CHANGING A MANIFOLD GASKET, HOW ARE YOU GOING TO CHANGE THE ENTIRE ENGINE ? YOU NEED SPECIAL TOOLS I.E. HOIST, ENGINE STAND, ETC.

 

Forgive my ignorance, but no ****. You don't actually think that I will attempt something like that and not know what the hell I am doing?

 

Matt,

there is no getting around putting a timing light on it if you want to fix the hesitation.

With that said, I suspect the accelerator pump on the carburetor.

Seriously. The timing is ~definitely~ the first thing to check either way. And you can buy an el cheapo timing light for what you will pay a shop to check it (unless you have a friend there). Do not forget to check that the vacuum advance is working properly!!!

But the hesitation you describe doesn't sound like timing to me, it sounds like on partial throttle acceleration it is not getting that big initial shot of gas it needs.

Unfortunately, there is no way for you in your present situation to get out cheap if that IS the case, even assistance in proper (and certain) diagnosis is going to set you back a few shillings.

My .02 - I know you'd rather have the cash

 

For what it's worth, my 77 F-250 w/351M has 298,000 miles on it. It's never been rebuilt. I did replace the stock timing chain at about 290,000 miles. It's got some of the same symptoms you indicate that yours does - I've got hesitation which I suspect is the accelerator pump. I just need to find time to replace it. The noise you describe does indeed sound like pinging. The EGR spacer plate below the carburetor can become caked with carbon which in some cases exacerbates the pinging problem - assuming all is right with timing, etc.

Don't give up on the M block. I wouldn't trade for mine.

Jason

1993 F-150 300 I-6 w/5-Spd.
1977 F-250 351M w/4-Spd.

 

Cost is not the issue, my parents will help me out.

What is wrong is what the issue is. I completley rebuilt the carb about 1 month ago. It worked fine for a few weeks and now that it is a lot colder I have the hesitation.
I doubt it is the fuel pressure, I recently replaced the fuel pump and added two inline filters prior to the pump and one after it, along with new soft fuel lines.
I checked the play in the timing chain as best I could with the method described above, there is no play at all, the rotor moves with the slightest force.

When I rebuilt the carb the PCV inlet was plugged and the entire base of the carb was covered in caked oil. I don't know how else to describe it, except that I believe the PCV valve had not been working correctly prior to my ownership of it.

I will get a new carb kit and try the accelerator pump. I will have to see about getting the timing checked.

 

You're blaming the motor when the carb and ignition timing are at fault. If you put in a Windsor or any other engine, it will run the same way with those problems.

Use some RTV Ultra Copper on that leaky manifold and kiss the leaks goodbye. This is the best stuff I have ever used. I pulled an exhaust manifold several years after using it, and the danged stuff was still pliable!

The common "wisdom" about running a 160 degree thermostat is one of those old wives tales that nobody should ever believe. An engine has an optimum operating temperature, and it needs at least a 180 thermostat to reach it. The problems that result from running too cold are many. Cylinder wear increases exponentially below 180. Sludge buildup. Sludge forms when water condenses inside valve covers and mixes with the oil. Water condenses when the engine is too cold.

I would almost bet that 160 degree thermostats were a ploy by car manufacturers to keep people coming back to buy new ones.

 

I will put the 180 thermostat, after I had two defective 180 ones I just put in the only one available at the parts store. Its supposed to snow 12 inches this weekend so I will have to wait until the road is plowed.

The plan with the motor swap was to use a crate motor, or simply rebuilding a windsor. I don't plan on keeping the M anyway, its not even worth the hassle. I know that a windsor and even a 460 get far better gas mileage and have much flatter torque curves.