Rod bearing advice - help please

MikeWire · #1 (**permalink**) 05-06-2008, 01:25 AM

So I have had a knock in my 390 - it hasn't been driven more than a few miles since it started, and I bought it as a hauler/work truck and not for show or the track. But I want it to run for a while so I can use it.

So here's my problem:

I pulled the pan off tonight to find that the knock is indeed a rod and a bearing that either has spun or has excess clearance on cyl #3 - I could move it back and forth a bit on the crank - the rest had very little play, but I didn't get my gauges out. So I popped the cap off #3 and took a few pictures becuse I don't know what to do. I don't need the the truck to be on the track, but just want it to be reliable and run good, but I really don't want to rebuild because I have other projects to do. This is one truck to help with the projects that need done, but the knock needed to be looked at.

So, what to do? Do I get a set of rod bearings and replace them all? Do I replace just the one? Do I do a rebuild...although I don't want to and don't need a new engine? It runs fine, but needs a carb tune, brake bleed and new front leaf springs.

All images - Index of /images/ford/bottomend

Pics below:

MikeWire · #2 (**permalink**) 05-06-2008, 10:32 AM

Really, nothing? I have already read a number of threads like this, and I read where people have replaced just one bearing with no problems, or have decided to do a full rebuild...so I dunno. It seems like this motor just has a few more miles on it than I thought (it came out of a 1972 F250) and this is bearing is worn the most because on the farm, oil doesn't get changed that often. Al l the other connecting rods felt fine, with minimal movement, if any at all. I runs fine other than the knock...

Can anyone tell me if the bearing and rod looks like they are toast?

I am going to pick up some plastiguage and see what the clearance is on #3 - can anyone tell me the torque on the rod bolts? Any more info is appreciated!

85e150six4mtod · #3 (**permalink**) 05-06-2008, 10:58 AM

When you run you fingernail across the crank journal, can you feel bumps/ridges/scratchs? It looks like you can. If so, you can't just put it back together with a new insert--it will spin as soon as you fire it up and you'll have your knock back and the march toward crank destruction or thrown rod will continue.

If you pull the crank and get it polished and put new bearings in, then the question goes to the rods. Do they need to be resized? And the rods have to go out the top.

Now you go back to the question of why this bearing failed...oil. Hhhhmmm. Better have the block hot tanked and rodded out.

See where this is headed....???

IF there was a way to secure the piston, I'd push it all the way up in the bore and pull the pushrods and plug wire and drive a V7 till I could do the rebuild. But you know that piston will migrate south...Then you'll have a real knock....

MAYBE you can get away with putting it back together, and pulling the pushrods and plug wire on this cylinder. That way, there will be little load on it and it's less likely to grenade until you do a complete rebuild. Get a strip of emery cloth and work over the crank journal a bit, put in a new insert and pray.

MikeWire · #4 (**permalink**) 05-06-2008, 12:14 PM

I'll check the crank tonight when I get home - the journal is pretty smooth, but from the pictures it looks worse than it felt with a fingernail, and the marks you see is more from the oil wiped off before I took the pictures, but I can see what you are describing and understand what you mean.

I guess my options are to put in a bearing and pray, lol - or to do a basic rebuild.

So the next question(s):

If a bottom end rebuild, then should I pull the motor and take the short block to the machine shop and have them do the teardown/assembly? I have most of the tools and skills to pull it apart and I could put it back together, but lack in experience as this would be my first "official" rebuild. Can anyone estimate the cost on the machine work to the block and rods? Should I have the shop resize the rods and polish the crank, or should I also have the cylinders honed and re-ring the pistons while it's there? Should I look at getting a new or reman short block?

If I go with smoothing the journal by hand and a new bearing...well it would be a band-aid fix I know, but how many FE owners have done this? What kind of results are those people getting?

Lot's of Q's, but the FTE forums are full of great info. Thank you guys!

MikeWire · #5 (**permalink**) 05-06-2008, 02:23 PM

I called around the machine shops and the prices are really fair. $100 to polish the crank, and anywhere from $40-$80 to resize the rods. Some shops will resize with the pistons on, others wont. So if I spent a couple of hundred bucks it looks like I can salvage the motor and have a good runner.

Anyone else done machine work like this, and do the prices seem fair? Like I have a choice lol...

Redmanbob · #6 (**permalink**) 05-06-2008, 03:24 PM

I'd do one of two things.
1. Take the cheap route and wrap the journal with 600 grit and rope it. Plop a bearing in and pray. Probably the best bet because #2 will be just that.
2. Pull it and spend the money to have it done right.

Tedybear · #7 (**permalink**) 05-06-2008, 05:04 PM

Friend of mine did the 'economy' fix on his family car. Repair lasted all of 5 minutes before the bearing spun again.

The best method would be option #2 that Red talked about. Keep in mind when a bearing craps out? It can send microscopic shards of old bearing material all over the oil system of the engine. Yeah it can make a mess.

If you choose option #1? Might increase your chances by using some plastic-gauge to measure the bearing clearance. Try with a 'stock' bearing first. You might wind up moving to a larger or "tighter" bearing to get the right oil clearance. (if that's the case? you'll want to re do the plastic-gauge to ensure it's not to 'tight' for proper oil clearance)

What happened to my friends car when he did the economy repair? The rod itself actually went slightly out of round when it nailed metal to metal contact. Had to get the crank machined, new bearings, new rod & cap for the defective one. The machine shop also sold him the correct new bearing set. And also hot-tanked the block to clean out the metal shards.

S-

MikeWire · #8 (**permalink**) 05-06-2008, 05:54 PM

Well after all the stories and suggestions I think I have decided to pull the motor and take the crank and rods in to get machined. It'll cost about $250 maybe a bit more, but I should be good to go afterwards. And I will get to know my FE a little better lol.

Thanks again guys - I am going to have the shop check the clearance on the wristpins as well, and are there any other suggestions on parts to take a look at or have the machine shop do when I have the parts there?

85e150six4mtod · #9 (**permalink**) 05-06-2008, 06:04 PM

The heads are off, the crank and pistons are out.... gee, what's left. THE CAM! Check to see if it's still got lobes everywhere, you should pull it, have the block hot tanked, if you're going to stick the pistons back in, if the cylinders are OK, have a light hone done and put new rings on. Don't forget to shop and ask around here as to what aftermarket cam to install, and since you'll be hospitalized for hernia repair after pulling the manifold, ask about intakes to. New seals on the valves while you're waiting.... you should go on with some of this, but it never ends till it's a full rebuild.

Good luck

Redmanbob · #10 (**permalink**) 05-06-2008, 10:46 PM

Quote:

Originally Posted by 85e150six4mtod

but it never ends till it's a full rebuild.

Boy ain't that the truth!!!

If your pulling the motor and heading to the machinist...it's now or never. If the funds are there no time like the present. However, if it ran good, had good compression, leak down test shows the lower/upper engine to be in good order. I'd stick to the plan (have the rotating assembly fluffed up, tear the top end off keeping a precise location of everything) Lap the valve, new seals, have the machinist check the springs for you /replace any that arent up to snuff. Tear the rocker assemblies down, mic/inspect and clean them up, install new plugs, .... you see where this is going.. new dizzy(prefered) or cleanup the old one... no reason to put a gunky ole shaft back in a pretty fresh engine... "closer to the flame"... might as well put a kit in the carb,

No seriously consider a reman before you get both feet in the holy **** patch.. If it's something that can be tossed back together and get you 50,000 miles down the road for 500.00 thats probably the best bet, a reman is gonna run 1400.00 + shipping and you have to hope like hell Dilbert at the shop did his homework. A quality job at a machine shop is going to run you that and you still have to put it together and install it.

MikeWire · #11 (**permalink**) 05-12-2008, 02:20 PM

Thanks to all the replies - I tore the front off the truck this weekend to pull the motor, at least down to the front clip. Can anyone point me to someones build up thread, or have any visuals on how to pull out the front clip? Do I need to pull the fenders? I want to just pull the whole front off so I can get my cherry picker in there.

MikeWire · #12 (**permalink**) 05-13-2008, 11:02 AM

Quote:

Originally Posted by MikeWire

Thanks to all the replies - I tore the front off the truck this weekend to pull the motor, at least down to the front clip. Can anyone point me to someones build up thread, or have any visuals on how to pull out the front clip? Do I need to pull the fenders? I want to just pull the whole front off so I can get my cherry picker in there.

Maybe I should call the front clip the radiator support?

Redmanbob · #13 (**permalink**) 05-13-2008, 01:23 PM

Mike did you run it through the forum for this year series of trucks ? Sorry never owned a highboy and never had any problems out of my 74' f100

Edit: might even run it by the guys in the slick 61-66 forum a lot of sharp folks in there

MikeWire · #14 (**permalink**) 05-13-2008, 01:39 PM

No I haven't gone to the 73-79 forum yet - but most of the guys like Mill1ion and ND cruise the FE forum too, so I thought they may have something. I was hoping to find a build up or teardown project thread. As a side note, I should document and make a thread for myself and others as I go through the process. I will do a search in other forums and maybe post a question or two as well - thanks for the tip!

Redmanbob · #15 (**permalink**) 05-13-2008, 01:43 PM

there was a guy here who did a highboy about 2 years ago ? 1975Ford user name I think. Search words might me (Ported, Highboy, headlight) he had a pretty extensive writeup on his work on that truck but cant recall if it contained what your looking for. However if you can find a thread by him and use it to PM him, quite sure he'd be glad to help with the needed info.

Edit: here is a link to his User CP stuff send a message is on the right..
Ford Truck Enthusiasts Forums - View Profile: 1975Ford