Hi. My first post here but I am hoping someone can help me.
I just bought a truck for my daughters first vehicle. Its a 1985 F150 4x4 with the 351W. It was a father and son project, they added a 3" lift and 33 tires but the issue I am having is the motor. It is not stock at all. The carb is an Edelbrock performer on an Offenhause intake. The distributor is an electronic Mallory. They said they put a cam in it for towing but I don't know the make or specs. We want to use the truck for towing her horse trailer but I am getting pinging when we are just pushing lightly on the throttle.
I have adjusted the timing which was set @ 5 deg ATDC back to the factory setting of 10 deg DTDC and the pinging still exists. We have tried mid and high grade gas also. I have replaced the plugs but am thinking I might have to go one range colder. It seemed to lose some power when I changed the timing but it made it idle much better when the vaccuum adavnce was disconnected. Before I adjusted the timing it would barely idle was the advance disconnected, I had a bear of a time keeping it running just to check the timing. I am thinking of putting the timing back closer to 0 deg to see if the power comes back a bit and also to keep the idle a bit easier to work with.
A bit long winded but my question is what else can I do to remove the pinging? All that is left is rebuilding and/ or tuneup on the carb? It is the last piece of the puzzle.
Thanks for reading and I hope someone can help. I am not a complete novice at this but I am new to this Ford horsepower stuff.

 

85 carbed 351W w/new dizzy & carb & vacuum advance - guess this means no EFI &
computer.

First thing to come to mind is the dizzy possibly being off by a tooth (hopefully not the
timing chain). Are the spark plug wires installed in the correct order. Possibly the dizzy's
mechanical advance can/needs to be be recurved. Is the vacuum advance connected to the
correct carb vacuum port. I don't know anything about a Mallory electronic ignition, did they
give you the paperwork & docs for it.

You should really check out/ask in the Small Block V8 forum, too.

 

351w in 85 had a carb originally. If it runs smooth with no dead miss, the wires are probably ok.

What I would suspect is the vacuum advance is not hooked to the correct port, and is also over advancing as they had a lot of advance stock. I have run into this problem before.

I have tried colder plugs, but they did not seem to help. I found it ran better with the stock numbered plug. What I did find that helped was to installed a 180 degree thermostat.

But the real culprit seems to be the vacuum advance. What I found works best is to leave the vacuum advance disconnected, and do road tests to see how far the dist can be turned and get the best power. I would turn the dist, and go for a road test till it started pinging, and then I would turn it back till it quit. On my engine this ended up being about 14 degrees BTDC. It had lots of power and good low end throttle response. After you do this, turn the truck off and let it sit for about 5 minutes, and then re-start it. If the engine struggles to turn over, then set the timing back a little bit till it turns over easily.

That will be your new setting for your particular engine.

Now the vacuum advance. If you try to plug it in, it's going to advance the timing way too much at part throttle. One note, I noticed you said you could not get it to idle correctly with the vacuum advance plugged in. If you have it hooked into the correct port, the vacuum advance should have no vacuum on it at idle. You should be able to plug and unplug it with no affect. If the port has vacuum, then it's the wrong port, or the idle speed is set too high and the throttle blades of the carb are too far open.

What I did with mine is run it awhile without the vacuum advance, and it ran good. But I wanted to try to use it, since it helps with fuel mileage, so I started experimenting with it, and I drilled a hole in the unit and started experimenting with different size pins(nails actually) to limit the amount of vacuum advance till I got it right. You can also buy adjustable vacuum advance units. But it will run fine if you want to leave it disconnected for awhile and see how it does.

 

Thanks for the responses. I spent some time on the truck today. I was all set to replace the plugs but when I started on the first one I found two things.
1. The plugs were new Bosch Platinums so I left them for the time being because.......
2. The first plug wire I pulled off left the metal connector behind on the plug.

I suspect some of the unevenness and lack of power was due to one or more bad plug wires. I had a terrible time finding plug wires. The local places don't carry Accel wires and the stock wires don't fit the Mallory cap. I ended up with a set for an early 70's Torino. They fit and are just a hair long.
The truck runs much better at lower speeds and around town. I don't get the pinging now until it warms up and around 45 MPH under light load.
Besides pinging the truck just seems to lack power and acceleration at highway speeds. I am going to order the parts from Summit to calibrate and rebuild the carb. The truck had been sitting for a year and I am hoping that it is just dirty on the inside. If the factory settings don't get rid of the ping I am hoping I can calibrate the cruise mode a bit richer to make it stop pinging. I am also hoping the rebuild/calibration will give it a bit more get up and go at highway speeds.
Now I just need to redo the valve cover gaskets as it seems one of them has developed a leak.
I am keeping my fingers crossed that it isn't the rear main also. Does anybody know if the rear main can be replaced with engine still in the truck if it is bad?

 

I also checked the vaccuum advance connection and it is connected to the proper port on the carb. I found the carb manual the web after I has able to clean the dirt off and find the carb number. It is an Edelbrock 1406 if that helps any.

 

i havr the same carb and after the eng rebuild with towing cam I had to ritchen the mixture.You'll have to buy a kit and read the section of the manual but it's pretty easy to do. Another thing I'd look into is your egr vlve, if i not working you may get some pinging

 

Thank you. I suspected as much. I just ordered the rebuild and calibration kits from Summit. That will be my task this weekend. I am going to set the carb up for the stock out of the box settings and work from there. I don't know what the previous owner has it set too although I am sure I will be able to tell once I get it apart.
I am hoping a good cleaning and some tuning on the carb will solve my problems.

 

Ok here is the update. I have spent all weekend working on this damn thing. I was able to finally able to get it to stop pinging under light load. The bad part is that I still not able to set the timing where it needs to be. The timing is supposed to be at 10 deg BTDC and I have it around 4 deg BTDC. I cleaned and rebuilt the carb and then used the calibration kit for the Edelbrock 1406 carb. I stayed with the stock jets for now. I had to go to the setup that uses the different metering rods and I used the stiffest springs they offer. The only thing left to try is the final combination of the jets and metering rods but I have to use the truck this coming weekend and I don't have any more time to play with it. It sucks because the idle wants to be really smooth around 12-15 deg BTDC but I can't run there with out pinging. I think after my daughters horse show this weekend I am going to send it to one of the performance garages around here to let them figure this out. I am at my wits ends.

 

All you have to do is try running it with the vacuum advance hose disconnected and plugged. Then set the timing at the 12-15 degree setting that you want. Then try it and see if the pinging goes away with the advance hose still plugged. It won't' hurt a thing to run it without any vacuum advance.

 

Thanks, I will give that a try as soon as I can. If that works then I need to dive into the distributor. I moght just replace the Mallory Unilite and coil with an all electronic version, maybe MSD or a newer Mallory.