Ok, I have spent the past few hours reading all the posts on Main Bearings, Seals and Crankshafts, great info here. I now know I can change the Main Bearings and Rod Bearings with engine still in the truck (360 in 1975 F100). However, I cant find the answer I have prior to opening things up. Which is...
I had a general mechanic (not a Ford FE guy) tell me that if there was movement in the crankshaft by prying on the flywheel, the block would be worn out and putting in bearings wouldn't solve the problem (knocking once warmed up). There seems to be a little movement, but in the opinions and voices of experience by the outstanding gents on this forum, is there no hope of fixing by replacing Main bearings? Could the journals or other be worn beyond repair? I have checked all other suspects, the truck has 89K on it, doesn't smoke one puff, has great oil pressure (I put in a new oil pump), purrs like new till warms up and the dang knock, which goes away when under load. I appreciate your help!

 

one of the main bearings is a thrust bearing, so know the block would not be worn...There should be some end-play in the crank...I'm thinking 20 thousandths max.

 

Crankshaft end play specs found here (on page 122):
How to Rebuild Your Big-block Ford - Steve Christ - Google Books

0.001" to 0.007"

Best way to check is with a dial indicator.

When you remove the caps you'll be able to see if the bearings are worn or not. If they are, then you will likely want to have your crank checked and if your going to do that well.... you might as well keep going and rebuild it because if the crank shaft and bearings are worn then so are your rods.

You can get a stethoscope and see if you can zero in on the area where the knock is coming from to ensure its in the rotating assembly and not in the valve train. You could try a heavier weight oil to see if it quiets down.

How long has it been doing this?

 

Thanks Kikkup. I have checked with a stethoscope and the noise is in the lower end somewhere. If the noise is a main crank bearing, won't it be worn? You say if the bearings are worn then you have to check the crank and may as well keep going. Do you mean do the rod bearings or have crank turned and do it all?

QUOTE=KIKKUP;13456112]Crankshaft end play specs found here (on page 122):
How to Rebuild Your Big-block Ford - Steve Christ - Google Books

0.001" to 0.007"

Best way to check is with a dial indicator.

When you remove the caps you'll be able to see if the bearings are worn or not. If they are, then you will likely want to have your crank checked and if your going to do that well.... you might as well keep going and rebuild it because if the crank shaft and bearings are worn then so are your rods.

You can get a stethoscope and see if you can zero in on the area where the knock is coming from to ensure its in the rotating assembly and not in the valve train. You could try a heavier weight oil to see if it quiets down.

How long has it been doing this?[/QUOTE]

 

Thanks DL do you think I may just need to change the thrust bearing?

 

Does your truck have an automatic trans?
It's not unheard of, but it is very uncommon to have the thrust bearing go out on an FE.
Years ago I had a similar problem with the same symptoms, this was on a '73 F100 w/ 360.
If it was idling, there was a very bad, very loud, very solid sounding knock. Once I put it under load, the knock went away. I did the exact same thing your contemplating, I changed the mains with the engine still in the truck.
Got it all back together, cranked it up, the knock was still there .
Make a long store short, the trans. flex plate had cracked almost all the way around the crankshaft flange.
Put in a new flex plate, knock was gone.

 

My Dad's truck (77.5, 400, 4spd) developed a knock with the same symptoms also. I swore up and down that it was a rod knock.
Turned out to be a bent push rod.

 

Hey Mike, mine is the manual 4 spd. I thought the noise might be coming from the clutch area and that's what I had the mechanic look at, but he said its lower end. Unfortunately, I am probably just going to have to do process of elimination like you did. The engine runs so dang good other than the knock when warm, I hate to do too much. Oh well, I''ve got 4 kids, travel 90% of the time for work, have almost no mechanical experience, why not take on another project that consumes the entire garage for the next 2 years like my furniture repair did right?

 

Rouge, so the bent pushrod only made noise when engine got warm? I took the valve covers off and the rockers were all moving. How did you diagnose, can you pull them out the top without unseating something important? Is the bend visible or did you have to have someone check it? Thanks!

 

Worn main bearings will not ruin the block. If the bearings were worn to the point of ruining the block, your engine would be making lots of unpleasant noises, not just the knock.

Since this starts when warm, and quits under load, let's think about the rod bearings. Since you still have good oil pressure, things are probably not out of control yet.

I would pull the rod bearings and check them for size. Replace them with new bearings in the correct size. My guess is you see a bit more wear on one than the others. Not good, so look for anything that would prevent oiling on that rod. Look at the crank also. If there is visible wear on the crank, your knock will be back quite soon.

Serving suggestion, ymmv.

 

I've done a lot of stuff with the engine in the truck and I've learned that as intimidating as it can be, pulling the engine and doing a rebuild is always simpler.

My first engine that I pulled was a 454 out of a boat. I didn't have any tools, knowledge or time. I knew that the people from my high school that were now doing this for a living were not necessarily the smartest people that I knew. I bought a book, a set of craftsman tools and rented an engine stand. I couldn't afford to pay someone to do it so I did the only thing I knew how -- figured it out.

10 years and 1500hours and that engine is still running.

That was my "stepping stone" and since then I've never been worried to bite off a project. Sure, my garage now has 4-5 projects in various states of "exploded views" but by just doing something (however small) every day I know that they'll eventually get done.

Good luck!

 

A diesel mechanic and long time Ford guy diagnosed the bent lifter by pulling the valve cover and placing his stethoscope on each rocker post until he found the knock.
Your 360 has a rocker bar assembly, different from the 400.
To pull the push rods you have to remove the rocker bar assembly, not a big job. Take them out one at a time so you don't lose which order they are in.
Here is some good info..

FE's That Bend Push-rods, A Dirty little Secret .: Articles

Also the book mentioned by tfurman6 has a ton of good info on these FEs.


Can't say for sure that this is your problem, just passing along my experience.

 

I'd guess I'd say do the pushrod check first--a lot easier than the bearing check and you might get lucky.

 

This wasn't my problem, but another possibility with a manual tranny is a loose flywheel. It would have the same symptoms. You might be able to check it by removing the dust cover on the bell housing and seeing if you can "wiggle" the flywheel back and forth, maybe using a screw driver or something.

 

Thanks for all the input guys, I guess the next step is turn off the computer, get off my butt and start turning wrenches! I'll let you know when I resolve the problem.