So I purchased my first ford truck this past May The title and truck supposedly have only 72k original miles. While the engine does not seem like a 72k engine I kind of believe it is original just because of the immaculate condition of the body, original paint, seat vinyl etc. It has not run right no matter what I do and recently developed a knock/click. I will list what I have done to date.
1. Carb kit + new float
2. New fuel pump (after I put the carb kit in it, the truck would run for a time and randomly die and when I disconnected the fuel line to the carb and cycled the ignition and pumped the gas no gas was being pumped out of the inlet, so I concluded it may be the fuel pump and replaced it)

• At this point it did not fix the random dying so I moved on to step 3.

3. All new rubber fuel lines from carb to aux tank as well as blew out all the hard fuel lines in between (I believe my main tank is clogged and has old fuel in it). I am currently running it off of the aux tank now
4. Dropped the aux tank put a new sock and float on the sending unit, cleaned out the tank painted it and reinstalled (gauge works now), the truck now at least does not die anymore and the fuel gauge works but it still runs rough with really rough shifts and would almost die if I laid the pedal to the metal from a stop
5. Changed the distributor cap, rotor, points, spark plugs and spark plug wires. Gapped the plugs correctly, set the points at .017, and even bought a timing light to play with the timing. While I could adjust the timing I do not know where specifically to set it. When I loosened the distributor hold down clamp and turned the distributor clockwise the truck would idle smoother and the rpm seemed to go up. So without knowing an actual number of degrees BTDC or ATDC I went by ear and let tightened it right before the engine started to bog down. So now it runs "better" but there is no power if I lay the pedal down, the shifts have improved a little but now any little movement of the pedal downward sends it into the passing gear (which has NO power). My mechanic took a look and gave me a compression test result that #4 and #7 were low at about 65 and 70 respectively. His thought was to do all the things I listed above in addition to lucas fuel additive, seafoam into the oil and trickling a bit of ATF in the plug holes to try and "free up" some potentially frozen rings and let them build some compression back up. It was kind of a last ditch effort type thing before a we conclude it may need a piston or two replaced.

So if you are still with me, the only two things I have not done are change the oil and trickle ATF in the plug holes. I live in Tucson and I do not think my neighbors would appreciate being smoked out but if that is deemed a good idea I can drive away out of town and do the deed. As for the oil at this point I have a hard time believing the oil is going to make the difference and if I am going to spend $50 to $60 to change it only to turn around and tear the engine apart... you see where I am going with that train of thought? Any thoughts on the situation, tricks of the trade? Do the ATF hail mary? Change the oil? Scrap the truck lmao? If the compression situation does not change is it possible to replace just the 2 bad pistons without pulling the motor?

 

Oil is cheap to replace along with a filter, if you haven't done it before. Just use cheap Walmart oil and a cheap Fram filter. If it doesn't work to free the rings, the engine is on very borrowed time and you will have to pull it. Pull it and upgrade to a 390 in the process.

 

I agree with RichS2659 on this. Change the oil and filter, use cheap 10w 40, clean oil is always a good thing for an engine I would also invest in a fuel pressure gauge and verify your pressure. I just went down this path with vapor lock on my 360 and found out the mechanical pump was weak with todays ethanol mixed fuel. I did the same thing with dropping the tank, blowing out the lines, replacing the rubber connector lines, and hooked the mechanical pump directly to a fuel can to verify it was the weakest link. I since changed it to an electric in-line Carter Pump and resolved that.

Sounds like you're on the right path here. Pull each plug individually and leave the spark plug wire on it. Have someone fire the truck over and verify it is getting spark. I'd bet on it being something simple first before contemplating the whole engine rebuild/replacement scenario.

 

Hopefully you didn't get any junk in the carb after you cleaned it...

Have you checked for any vacuum leaks?

FE engines have a initial timing of about 6 degrees before TDC as far as i know, but some people say a timing of 10 - 12 before TDC wakes them up alot.

If you want to set your initial ignition timing make sure you disconnect your vacuum advance of the distributer and plug the line (otherwise your carb pulls air from that line). Use your timing light to find your desired timing.

Another thing you could try is letting the engine idle and than pull each individual spark plug wire off of the distributer and see if it runs worse, if one cylinder doesnt change you'll most likely have found your problem.

My last tip is pulling the valve covers after the engine warmed up and check if the rockers are tight. They shouldn't move. If you can push them down you'll have a bad lifter. That might be the reason of your ticking.

 

I would do the seafoam and ATF treatments before changing the oil. An oil change will not help the low compression. I can say that if the engine is original I can almost guaranty that the timing chain needs to be replaced! The top gear has plastic on it that breaks done and makes timing useless.

 

@fe390pc yup dump a qt of cheap atf in the oil and run it, the detergents in there might loosen up a stuck lifter but theres a difference between a knock and click and no amount of oil changes will fix a knock whereas a click can be resolved this way

 

Good idea. Ill change the oil and filter. Is there any literature you recommend on rebuilding with potentially upgrading this engine? Seen a few books on amazon that are reviewed well BUT not sure if these are just a stock rebuild or give options on upgrading components.

 

So i have a vacuum gauge, can i use that to check fuel pressure? I will try that spark idea as well. Im hoping it is something simple.

 

I havent checked for vacuum leaks. I have a gauge I just bought but its a little overwhelming the amount of things/variables in this equation. What should I do "first" tune the carb, set points, set timing, trickle atf in plug holes, check vacuum? How does one check vacuum? I have heard the terms ported and manifold vacuum thrown around but I do not know the difference. As for your spark plug tip if the engine does not run any different are you saying its safe to conclude that cylinder is not getting spark? IF thats the case is it a bad wire? I will try the valve cover tip as well. Thanks!

 

I'd be curious if your mechanic did a "dry" AND wet compression test. If those cylinder numbers raised up during a "wet" test, that points to the rings . Since your 1969 is before 1972 when Ford put hardened valve seats in the heads you could have some burnt valves and sunken valve seats. Which would cause loose valvetrain and knocks. Your vacuum gauge will tell you more than you think. Hook it up to a vacuum nipple on the intake manifold. This is manifold vacuum. there will be vacuum there at idle. Ported vacuum is a vacuum port on the carb that is above the carb's throttle plate. There is little to no vacuum there at idle.

 

My first thought after reading the OP is this: you cleaned out the carb and put in a carb kit and new float first, and then put in a new fuel pump, and then blew out the fuel lines and switched to an ostensibly “clean” aux tank. Ideally things should be done in reverse order, so that no debris from the tank or lines makes it into the carb. It doesn’t take much to plug up a carb enough to cause symptoms like yours (rough running, random dying, sputtering and dying from a stop). I would put a filter in line with the tank, run it a bit, and see what accumulates in the filter. If it plugs up quickly, you still have lots of junk in the lines and the tank despite cleaning it. If it catches some stuff, but doesn’t totally blind off, then I would keep the filter in there and clean out the carb really well. See if that solves your issue. To me, it sounds like a fuel issue. Or at least, like it’s running real lean. Which could be either fuel delivery, or a bad vacuum leak. You can diagnose the latter pretty easily with a vacuum gauge.

 

I suggest setting the timing first. It's done pretty fast and easy. You can check if your timing chain is in good shape by taking a ratchet to to your crank and move it back an forth just a bit while watching your distributer rotor. If your rotor moves immediatly your timing chain should be fine.

I personally run manifold vacuum. You should check all those rubber plugs on your carb and all the rubber hoses. If they are gone or have a hole thats obviously a leak. change the PCV valve... they can make problems when it comes to vacuum, but not as bad (dont quote me on that)

About the spark plug tip... This just tells you that something is wrong with that specific cylinder...either a faulty wire/plug or no compression. Could be anything, but gives you a starting point.

I 100% agree with sparky72...

 

Timing doesnt matter if there are cylinders with low compression. This is the first and highest issue. Perfect timing wont make a bad motor run any better. Before doing anything else I would do the seafoam treatment and then rerun the compression test. If there is improvement then you can start on oil changes and timing. What Jefffafa said about the valves is another thing to check with a leak down test. You may be instore for a refresh.

 

I will ask him when I take it back this Thursday. He gave me a list of things to do on my own so I can save some money and we can determine whether the compression improved or not. Thanks for clearing up the definition of ported vs. manifold vacuum for me. As an update I adjusted the timing to 12* BTDC. It runs a lot better. Come to find out after lightly sanding my fly wheel that it was set at 2* BTDC. I believe what it is feeling now is just a vacuum leak somewhere (in addition to the low compression on the two cylinders). So today I will work on replacing all the vacuum lines I can get my hands on. Where is the PCV located? Rear passenger side valve cover? I thought it was the oil filler cap which is in front of the drivers side valve cover but there is a similar one on the rear of the passenger side valve cover. I could replace both... There is a hose that goes from the oil filler cap to the air intake.

 

The PCV is located towards the back of the valve cover on the passenger side and the hose connects to the back of the carburetor spacer plate. Pull the PCV and see if the little ball moves inside and inspect the hose for cracks. If the hose is good and the ball moves, I'd leave it alone. The oil filler cap on the front driver's side has a hose that goes to the Air Breather which completes the crankcase ventilation system.




When you say you sanded your flywheel, I think you mean the harmonic balancer. If I could recommend something, get some literature on the FE engine and watch some good youtube videos (Power Nation, Thunderhead 289, Uncle Tony's Garage) on the basics. This is how I learned along with the hands on experience we're all getting. Take a step back and start a list:

1. Do you have spark at all 8 cylinders?
2. Do you have good air flow?
3. Do you have fuel? I still vote to bypass everything and have a fuel line go to a gas can to verify the lines/tanks are at fault.
4. Do you have any vacuum leaks? Intake, hoses, distributor vacuum advance diaphragm...

Don't get into a major hurry and start throwing parts at it...slippery slope and extra money spent. I've been there.