We recently purchased a 1980 F-350 for pulling our equipment trailer. The engine is a 351M. It was fitted with an Edelbrock 400 4 barrel manifold. Has a Edelbrock 600 or a 650 carb. We were told that the manifold was cracked or just leaking vacuum.
we replaced the entire manifold out with a new one, and the engine seemed to run better. At mid range the engine really missed out. If the timing was set according to the spec.'s at 3 degrees BTDC it wouldn't hardly run at all. We installed a new distributor along with spark plugs, plug wires, rotor and cap, also went ahead and changed out the timing chain and gears. Runs alot better now with more power it has ever had, but setting the timing as sepecified with the vacuum advance hooked up, it rattles as if the timing is still off. We unhook the vacuum line and it rattles only slightly. We set the timing at 5 degrees ATDC and unhooked the vacuum hose, and it has no rattling. At idle it still runs rough. If you hook the vacuum hose back up, it starts rattling again. It is also down on power again. Please Help!!!

 

HES,

Does it rattle (sounds like you are describing pinging) at idle or while driving? Make sure to time it with the vacuum lines disconnected from the distributor and plugged.

When you bought the timing gear and chain, did you get for a 1980 year? All cams were retarded by 4 deg after 1971. My 351C is a 1972 and had a retarded gear set. Aftermarket gear sets usually have a keyway for -4 deg, 0 deg, and +4 degrees.

Do you have a dual vacuum (not dual point) canister? If so, make sure the connection farthest away from the dist (usually points straight away) is hooked to the timed port of your carb. The closer vacuum hookup goes to the manifold. If these are switched, then your symptoms make sense.

Do you have an EGR setup. If you are running a 1980 engine, there probably is one. That could be a big source for your rattling.

There are many more qualified people who will be lending a hand, but hopefully you have some things to look at.

Steve

 

Steve it does ping only when you are leveling off on the accelerator. When under power it runs fine, no pinging. It was fitted with a single vaccum advance system. No EGR is connected. As far as the gear marks, they all were marked the same as the original, and went on great. Have tried all the vaccum ports off the carb. , but not the port off the manifold. The others didn't help one way or the other.

 

HES,

Don't hook up the vacuum to the manifold since you only have a single vacuum advance, it needs to be hooked to the timed vacuum (I think the passenger's side on an Edlebrock carb).

You also might have a huge buildup of carbon on your pistons and in your combustion chambers. I had this problem about 7 years ago on my Cleveland. There are a few ways to get the carbon out. I used the steam method. But before you do that, what does your timing light indicate at idle, 1000, 1500, 2000, 2500 and 3000?
Knowing what the timing is at these points will help to diagnose/rule out what is causing the pinging. When I replaced my stock distributor, the mechanical advance was set on 13 which is 26 deg on the crank. If you have a stock 1980 Ford dist, then there are two mechanical advance settings. Normally 13 and 18. You have to multiply the number in the distributor by 2 to get crank timing which is what you are reading with the light.

Let's look at it this way, if you are at 5 deg BTDC, vacuum advance is usually 10 deg, and the mechanical is on the 18 (36 crank deg) setting, then you have a whole heap of timing that today's gas won't support.

You can unhook the vacuum and plug it. Set the timing according to the label on the hood, then have someone slowly bring up the idle and watch the timing as it advances. Then hook up the vacuum and write that down. I believe your vacuum canister can be adjusted like my '72 by sticking an appropriate sized allen wrench in the vacuum inlet. Someone will have to answer which way to turn it for me, as I don't remember. But you may be ok.

I am running high cumpression and have a whole different set of challenges, but I only have a total of 34 degrees all in at 3000 rpm.

Sorry for the long and not so comprehensive answer, but there are still many other things that could be causing you to ping. You said that your engine also runs rough. That sounds like a vacuum leak. With a vacuum leak you run lean and that could cause pinging. You need to hook up a vacuum guage to the manifold or the driver's side of an Edlebrock carb and it should read at least 17 inches on your engine.

Steve

 

With vaccum gage hooked up it reads fine where it should. Indicates no vaccum leaks as well. Still can not hook up the vaccum line without it pinging at mid range, or leveling off.

 

Still having the timing problems. Have checked the vaccum and it reads fine. The only way so far to get rid of the pinging is to set the timimg at 4 degrees ATDC and not hook up the vaccum hose to the distributer. Need more input for trying to solve this problem.

 

theres definatly a problem, is the timming chain set a tooth off in the motor or distributor off a tooth? but you still have a issue with vac line, that line should not have any vac on it at idle, ther fore it should not matter if its hooked up, if you have vac on that line at idle then its hooked to the wrong place on the motor. DW