I recently bought a 1982 F 350 grain hauler.
It has the 400 engine in it.
When I bought it, it wouldn't run.
I was told the heads were in bad shape, so I had a valve job done on the heads, and had them planed to be true.
After installing the heads, I went to start. It ran for 10 minutes, and it developed a miss.
Upon pulling the valve covers, I had bent push rods on cylinders 5,6,and 7.
I pulled the heads, and nothing looked like the pistons hit the valves. Nothing had marks, so I pulled the timing cover.
It had the original timing chain. There was only 1 nylon tooth covering broken off, but the chain was really sloppy.
So I installed a true roller timing chain set. It gave me the option of setting it at 2 degrees btdc, at tdc, or 2 degrees after tdc.
I installed the chain on the gears at tdc.
So after I put it back together, I fire it up, and it is running rough, as it had old gas in it. I added fresh gas, and it still missed. Upon checking the firing on the cylinders, I was getting no spark at cylinders 5-6-and 7.
I had new plugs and wires by the way.
I pulled the valve covers, and I found the pushrods for these cylinders bent just like the first time.
I know I have the timing chain set lined up, but I have no clue as to what the heck is going on.
Before I fired it up, I had rotated the motor at least a dozen times, while setting the distributor, and to check for any pushrod interferrence, and had none.
I also noticed, after I had it running, ther I was getting oil up around the distributor.
Can anyone explain what I am doing wrong.
I had gone on a Ford engine site, to get the timing specs, firing order etc.
I am at wits end on what to do next.
This is a great old truck, and I don't want to have to put another motor in it.
While you are at it, since this truck is mainly used around the farm, I want to simplify things, and remove the polution pump, and all unnecessary vacume hoses, and crap on it.
If you have a diagram on how to re plumb it for vac hoses, I would appreciate that also.
I appreciate any and all advice.

 

When you had the valve job done, did they replace any valves?? If so I'm wondering if the valve stem is too long. Or the seat is ground down far enough the valve stem is sitting high..

You might try a straight edge laid on top of the valve stems to see if this is the case.. If they are just a few thousandths long you might be able to get a shorter pushrod to compensate for the stems..

 

I don't remember the details from assembling my own 400 engine, but I remember there are measurements that can be taken of the gap between the valve & rocker arms.

You'd need a feeler gauge.

One can install shims if the gap is too large, or shorter push rods if too small.

The following book I'd bet would have the details, I got a used copy at Alibris:

Amazon.com: How to Rebuild Ford V-8 Engines (9780895860361): Tom Monroe: Books



Might also ask in the 335 forum here on FTE.

 

I don't think the pushrods being too long or short would cause them to bend. It would have to be radically long, and the engine would not have run right from the beginning. What I would do is get a valve spring compressor, and take apart the valve assembly. Or come up with something to depress the valve while it's still assembled. I am wondering if a few of those valves are too tight in the valve guides, and are stuck.

If you find they are stuck, that's your head rebuilder's fault.

 

I'm thinking the same thing, either too tight valve guides or too high spring pressure/too many shims to bring seat pressure back up causing lack of travel.

 

To pull the valve springs and check for the valves being frozen, put that cylinder at TDC and put compressed air into the cylinder via the spark plug hole. I did this by making an adapter out of a spark plug. Took the insulator out and tapped the remaining hole for a pipe fitting, maybe 1/4" NPT, and ran a fitting in there.

Note that the piston must be at TDC or very close or the air pressure will cause it to go back down the bore. But, if truly at TDC it should stay there while you pull the springs off.

 

I like the idea of the valve guides being too tight. That may be a good answer.
This is what I've thought about and will add to the fire.
When I bought the truck, it had one pushrod bent on the passenger side.
I took it apart, had the heads done, and ended up having one pushrod on the pass. side bend, and 3 on the driver side.
This last time, it was the intake pushrod on cylinders #5-6-and 7.
I've gotten good advice so far, but I need to state what I've done the last day.
Tore down, to make sure the timing gears are timed. OK
Pulled the distributor, to see if the roll pin on the gear was sheared. OK
I've had 4 people who are familiar with engine rebuilding, and some are leaning toward timing.
A friend who is an engine builder for a lot of dirt track racers, but builds mostly bowties, mentioned about if setting the distributor into the block at a precise or close to precise way, will cause misfire, which would cause bent push rods.
Just because he specializes in bowties, I respect him for his candor, in trying to help figure out the problem.
How critical is it to dropping the distributor into these engines? I recall that I had a prior experience with a friends 351c engine, and had timing problems, after installing a timing gear set.
Tomorrow I am pulling the heads again, and having them looked at, to see if the guides are too tight, and swell shut when warmed up.
If I can get this figured out, hopefully someone in the future, who has the same problem, can find the answer too.
How critical is it to dropping the distributor in correctly?
I forgot to mention, but here goes. After turning the dist. back 1 tooth, and getting it running, I tried setting the timing. I couldn't hit the mark with the timing light, and moving the distributor in advance, or retard, did not make any difference.
I could turn it to retard, and it would start to die out. Turning it to advance, I had no improvement until I got too far advanced, that it would die out.
I bought a new distrubutor, to see if that may be causing problems.
This truck has only 53000 miles on it, and is far from tired.
PLEASE! anyone with some insight, please speak up!
As I said before, I appreciate any and all suggestions. I will report if and when I do find the culprit, so no one else has to go though what I am, with this engine.

 

I don't think ignition timing is the issue. All that can do is to make the engine run better or worse, or not at all. But, even a backfire will not bend a pushrod. The only thing that will bend a pushrod is trying to open a valve or rotate a rocker arm that is reluctant or unable to move.

Unable to move means very tight guides, way too strong of springs, or valves hitting pistons. If it is tight guides you really don't have to pull the heads to figure that out. Ditto for the springs as it would take something like double springs to do it. As for valves hitting the pistons, you would have bent valves as well as push rods. Which begs the question - do you have bent valves? What kind of pistons are you running? How far down in the block do they sit?

Reluctant to move might mean tight everything and/or way too much cam lift. What cam are you running?

Again, I cannot see how ignition timing could in any way bend push rods. I firmly believe the discussion about the distributor to be a red herring. It has to be a mechanical issue - valves that are unable or reluctant to move at the rate you are asking them to move.

 

We are going to pull the heads today, and have them checked out at a local engine shop.
I agree the ignition timing is not the issue, as I've seen, and had major backfires, and not seen a bent pushrod either. I'm just trying to say what was discussed etc.
It probably doesn't take much time for the head to build heat once running, and if the guides are too tight, maybe they shrink down, and cause a seize.
Will know hopefully sometime today.
In the mean time, keep your thinking hats on......

 

These engines are non-interference engines, meaning no matter how far the timing is off, the pistons will never hit the valves. The only way the valves can hit the pistons is if you are running some sort of hot cam, with different pistons and the block decked or the heads shaved severely. In other words, only the highly modified racing engines worry about interference, and they use modeling clay and take the engine apart several times to check this.

Some of the foreign engines, and some of the newer designs are interference engines. Those are the ones you hear about breaking a timing belt and then it bends the valves.

 

It almost sounds like you may be getting coil bind on the springs. Some machine shops just arbitrarily shim the springs. Have you tried swapping the heads side to side? If the problem follows the head then I would be having a serious discussion with the machine shop. If it stays on the same 3 cylinders, then I would start by checking the deck height on those 3 cylinders.

 

One other thing that I noticed no one had asked.. How much was ground off the head deck to make it true again? Did you check for valve clearance when you put the engine back together?

 

When the head is re-surfaced and the valve seats are ground, this does change the relative height of the valves to the cam, and the head rebuilder is supposed to grind off the proper amount on the valve stem tip to make it all come out right again, since the valve train on these engines is not adjustable. If it's way off, then the engine will not run correctly if it all(valves open all the time) or you will get a lot of ticking from the valve train(valve stem to to rocker is too loose, and the lifter runs out of adjustment). This still should not bend pushrods.

 

Before pulling the heads, I talked to the engine shop I was going to take the heads to.
We discussed what I found out from you guys on this site.
He suggested ordering a couple different length pushrods ( 1 each) and trying them on the cylinders that are bending them.
If we find one that doesn't bend, we will go with that.
To me this sounds a little off the wall, but what Dave F said about having the valve stem ground off does, and installing shorter pushrods may do the trick. The only crappy thing about that is, the time it takes to order the pushrods. Well at least I may not have to pull the heads again.
Will keep you posted.

 

Custom ordering pushrods can be expensive and takes time. I would suggest pulling the rockers on 5,6, and 7 and remove the old pushrods. Then pull a pair of stock pushrods from another cylinder. Turn the engine over by hand until the valves for cylinder 5 is on the base circle of the cam. Install the stock pushrods and install the rockers, but only tighten them down until you reach zero lash without compressing the lifter at all. Then slowly tighten the rockers and count how many turns it takes to bottom out the adjusting nut AND watching to make sure the valves do not start to open at any point. It should only be something like 1/2 turn to 1 turn to bottom out the rocker nuts and the valve should not move. If it takes more than that, or if your valves start to open, your pushrods are too long.

If the nut bottoms out in less than 1 turn, then slowly turn the engine over by hand until each valve is fully open and check for spring coil bind. Watch the springs and stop turning the crank if the coils bind, or you will bend your straight pushrods.