I bought my 64 F-100 about 4 years ago. It looked pretty good, no rust, been repainted, but still red. It has never really run smoothly. I have done a lot of work on her. Brakes, King Pins, rear axle seals, clutch, rebuilt radiator, rebuilt carburetor, master cylinder, regulator, rocker arm assemblies, fuel filter. I did the rockers because when I adjust the valve lash, she seems to run better at least for a few days. I thought it was the original self locking rocker arm adjusters, so I replaced the assemblies and the new rocker arms have adjusters with nuts that lock against the rockers. I don't know how they could be getting out of adjustment when I have locked them in place. Also I just did a compression test and got a pretty even 100psi on all 8 cylinders. I had a friend listen the engine and he thought it might be electrical. I checked the firing order it was correct 15486372. then I started pulling off the spark plug wires to see which cylinder might not be firing. #1, 2, 5, 6 all seemed to make little or no difference, in fact, I can remove all 4 and it runs just the same. without either #3, 4 or 8 it will not start, #7 only makes a small difference. When #1, 2, 5 and 6 are all off and #7 is pulled the it runs much worse. I think it is a small miracle it runs at all on only 3 or 4 cylinders, you can call me crazy, but I would prefer to have all 8 cylinders running.

What can this mean?

I have had the intake manifold off, and it was not obstructed. I had a mechanic set the valve lash for me and adjust the carburetor, and he never mentioned that it might not be running on all cylinders. Not going back to Tony ever again. Does this make sense to any of you? Does it sound familiar?

 

With the engine running and valve covers off, check to see if each of the pushrods are rotating. You may need some good glasses and a light. Look carefully. If one or more arent rotating, it usually means a bad lifter and/or cam lobe, although sometimes due to wear a pushrod may have a burr or other defect preventing rotation. Valve lash should only need a check each year or so, and if not many miles have been logged lash basically wouldnt change for several years. If the cam/lifters are failing, they can wear quickly and cause lash to open up, requiring much more frequent adjustment.

Assuming the compression test was done with engine warm, all plugs out, and throttle fully open, 100 psi sounds like it is tired.

 

The compression test was done with the engine cold, all plugs out. i did not touch the throttle, so it was closed. I used my remote starter switch to turn the engine over to get the test. 100psi was the first compression stroke, if I let it turn over a couple more times it reached 140.

 

It's odd that all of the front cylinders exhibit the same characteristic. It rules out carburetor and therefore fuel problems because those cylinders are fed by each side of the carburetor. Compression is great if all 8 reach 140 so that should not be a problem, though the throttle should be wide open when performing a compression test. Given that you have fuel and compression, you must not be getting spark either at all or at the right time.
Have you checked for spark at those cylinders? And just to be sure, you know that #1 is the cylinder at the front of the engine on the passenger side?

 

I have an original shop manual, so I did know that #1 is front passenger side and #8 is rear drivers side. I am getting spark I checked 1, 5 and 6 when I was changing the plugs last week. I am starting to think it may be that the valves are not opening all the way. Bad lifters or bad cam lobes might allow the valves to close, giving a good compression test, but if the valves don't open properly the cylinder is not going to fire correctly. It may also account for the lash getting out of adjustment in just a couple of weeks. I may need new lifters or a new camshaft.

Replacing the lifters would be easy, the camshaft will be a reach for me as a shade tree mechanic. I can't afford to have a mechanic do a camshaft, so I will have to learn.

But what would be the fun of owning an old truck if it just ran perfectly all the time?

 

Well, the bad news is that for practical purposes, the engine needs to be out of vehicle to get the lifters out. They are mushroom lifters, removed from the bottom side of the valley pan.

There is a rare tool that used to be available, to allow removal and installation of lifters through the cam bore from front of engine, with cam removed. A friend happens to have one of a handful that are still around.

 

Just to make sure, NEVER just replace lifters OR a camshaft. Always replace together. Just my 1¢.

 

According to my shop manual the tappets can be replaced while the engine is still in the truck. The camshaft must be removed, but once it is out of the engine the tappets can be replaced.

The question is after I do this will it run like a top? I replaced the rocker arms thinking I would then have this thing licked. Not so much. And that was easy compared to pulling the camshaft.

 

Just to make sure, NEVER just replace lifters OR a camshaft. Always replace together. Just my 1¢.

That makes sense. As long as I have it all apart, I might as well replace it all, but then where do I stop, what about the camshaft bearings?

 

It can be done but like Mike said it is a Be-atch. The lifters have to come out the bottom and fished tho the cam bearing. Then you have to put the new ones back in the same way. Once in place you will have to hold them up with clothes pins or a like device.not fun. You will probably end up pulling the pan to retrieve the ones you dropped.

 

I think the oil pan has to be off to get them out in any case. replacement sounds like a two man job, one to insert the tappet from below reaching around the crankshaft and one to catch it on the top side.

This sounds more and more like fun all the time.

 

Your going to need some long a$$ fingers to "reach around the crankshaft".

 

I think that if the lifters could have been installed with engine in place, pan off, crank in, the tool I mentioned never would have been made.
What does your shop manual say about the technique used?

 

It's easy to check for flattening lobes. Remove the valve covers, start it and watch the valves. Are the valves for the front four cylinders opening noticeably less than the rest? If it's bad enough to cause a miss, you will see a diference. If this is the case, then you may even notice that the adjuster screws are farther in than the rest.

 

Why not start by checking the lift at the pushrod? Before we start replacing the lifters and cam let us do some testing first!

It has been my experience that about 60% of engine probloms are electrical. IE Bad wires, cap or poorly set ignition. I have chased fuel gremlins in carbed engines in circles only to find cracks in plugs or loose connections in wires.

Also what about bent pushrods? If you tighten them down they will simply bend some more after a few miles?

I say do some good tests before yanking a cam, crank, and lifters. Take the pushrods out and check to see if they are bent. Verify the vlave lift.

Although you can do it in the truck pulling the engine is alot easier to change the lifters. And yes a shade tree mech can do this if they have paitience and the correct tools.