I need help?

crushnut · Mar 14, 2004

How serious is a loose wrist pin? I found out that the pin on the #4 cylinder is loose and making noise. I have been told that other than the noise it makes, that this isnt a real big deal or anything to worry about and does not warrant tearing apart the engine and fixing it. This really isnt an option since it is my daily driver and only source of transportation. Is this true? Should i be worried or just drive it and forget about it? Engine experts i need your help and input :worship:

Thanks

Mach1steve · Mar 14, 2004

thump in your pocket-book

I am not an "engine expert" but the simple rule here is, if there's a knock, there's play, and where's there's play, there's wear, fatigue & part failure.
Lets say you leave it alone....... it breaks and punches a hole through the side of the block (and it will, where else can it go?)... now you need a complete new block & rebuild and lord knows what else it will "hand grenade" with it !
If you know it's bad, fix it before it costs you triple or more !

just my humble opinion.
better safe than broke !
Mach1steve
www.muggziperformance.com

68GEETEE · Mar 14, 2004

I think you need to get it fixed before it does serious damage to your motor.

6Stang7 · Mar 14, 2004

Who told you it was a loose wrist pin?!?!?! Does it just make a knocking noise!?!?! Ford wrist pins are pressed in, so them coming loose is near next to impossible. If it does make a knocking noise, then what you might have is a rod knock, which is very serious. Imagine the bearings for you 4th cylinder rod worn out, so that you rod is has enough slop to move around on the crank journal. Now, I don't know if what your engine is (289, 302, 351, ECT), but lets say it's a 302 (to make this simple). The stroke on a 302 is 3" (distance from top dead center to bottom dead center). At idle, one cylinder fires about 8 times a seconded, and for every time it fires the piston has traveled though the 4 strokes (not really, but this makes it easier to understand). So, every time the spark plug fires, your piston has traveled 1 foot (3" times 4 strokes = 12") so at idle, your piston moves 8 feet per sec. Now this may not sound too bad, but remember that is this a up and down movement, not in one direction (look at my avatar). You have a piston traveling at 8 feet per sec bouncing around on the journal of the crank, and this is only at idle! You need to get this problem fixed A.S.A.P. If you do have a rod knock, your engine won’t last long.

hdgapeach · Mar 14, 2004

Wrist pins are peculiar items. When bad, they may last forever, or just fifteen minutes or less. The easy consideration is wheather to gamble with the timing of the fix. High risk is you bet you get around to repairing it sometime in the future before it breaks loose and does the Tazmanian Devil dance inside the block. This translates to you possibly could have to replace every single component inside the block, possibly both heads (probably atleast one), and almost guaranteed you will need a new block.
The low risk solution is to go ahead and take a weekend and fix the thing. Pull a pan. Pull an intake and one head. Get number four out and switch the bad for new. You tell me which will be more economical!

crushnut · Mar 14, 2004

How do i determine that it is a worn rod bearing rather than a wrist pin without tearing it apart right now, this is my daily driver i have no other car to use. How do you change the rod bearing, is it just dropping the oil pan and changing it out with a new bearing? Should you do just that one, or all of them be done then?

crushnut · Mar 14, 2004

BTW- Its been this way for about 5 months

6Stang7 · Mar 14, 2004

Yes, you just drop the oil pan, and un-bolt the rod cap. You can then change both halfs of the rod bearing. I can't imagine it being the wrist pin, as those suckers are squeezed in there tight ( I have tired to remove them before).

-Shaun

GaPonyFarm · Mar 14, 2004

These things are impossible to verify without looking inside. I have serious doubts thats its a wrist pin (and that diagnosis would be nothing more than a lucky guess), but it could quite easily be a rod knocking. If its been going on for 5 months, you're either not concerned or its not bad enough to scare you.

The way I see it, you can either go to the trouble of looking inside, or you can buy a new engine, so that you'll have one ready to drop in, when yours breaks.

Just because this is your only source of transportation, doesn't mean that it can't be in serious need of repair. Walk a day or two now, or get used to walking alot, later.

crushnut · Mar 14, 2004

Ok thanks, should i replace them all while im under there doing that, or just the one(s) that need it?

crushnut · Mar 15, 2004

Also what is Plastigage, and how do i know what size bearings to get? Im trying to get this all together before i start, so i have all the things that i need to do this right the first time. I really dont want to screw this up.

Thanks

crushnut · Mar 15, 2004

Nobody knows?

6Stang7 · Mar 15, 2004

crushnut said:
Also what is Plastigage, and how do i know what size bearings to get? Im trying to get this all together before i start, so i have all the things that i need to do this right the first time. I really dont want to screw this up.

Thanks

Plasticgage is a system used to messure the clearence between your bearings and the journal of the crank (to make sure that you'll have enough room for oil to get between the bearings and the journal). The bearing size should be stamped on the old bearings; however, if the are not, then you will need to mic the journal to figure it out.

-Shaun

crushnut · Mar 15, 2004

How do you recommend checking the bearings and wrist pins once i get the oil pan and pump out?

Also, should i do them all while im down there?

6Stang7 · Mar 15, 2004

Looking at the wear on the bearing will tell you how it has been riding on the crank journal. If you can post pics of what they look like, I can tell you how they are riding. As for replacing all the bearings; it would sound like a good idea to do, but I am not sure if you would have to go through another break in period of some type (although, I wouldn't assume so). Now, are you really worried about the wrist pins? Do you know of a good mechine shop around were you live? I would ask them what their thoughs are on a loose wrist pin (the likly hood of it happing). The reason I suggest doing this is because to really check the wrist pins, you have to pull the piston out. To put them back in (correctly) you have to remove the cylinder heads, which results in more work.

-Shaun

crushnut · Mar 15, 2004

Ok, yes i do have a machine shop that i can call and find out the likely hood of loose wrist pins. I plan on tackling this in the next few days and i dont really have the time to go and pull the intake, heads, and pistons out. If the clearance of the other bearings are within the desired specs, and look ok they shouldnt need to be replaced then, right? I was told that replacing all of them at once can open another can of worms if they dont all need it, is this correct? Thanks for all the help

6Stang7 · Mar 15, 2004

I have never heard of this before; however, I'm only 18 and have only be working on cars for about 2 years. Your best bet will to also ask the mechine shop that question. You shouldn't need to check the clearance of the other bearings though. If there wasn't enough room, you would have more then likly burned the motor up by now.

-Shaun

GaPonyFarm · Mar 15, 2004

You also want to make sure there isn't too much clearance... Too much clearance is as bad or worse than too little.

As far as piston removal & replacement, if you're not willing or able to pull the heads, you're wasting your time. The cylinder is tapered at the bottom.

Bad Snake II · Mar 15, 2004

Crushnut, the thing about the wrist pins are they are pressed in. I take my extra engines into my maching shop and he lets me press the pins out myself. It takes 2300 pounds of pressure to push one out and that is some of those that are in engines that have 300,000 miles on them. I highly doubt it is a wrist pin, but it could be and if it is it is floping around in there already and the damage has been done. The knock could be anything, my engine after i rebuilt it has a knock, will probubly never know what it is but the best guess is my cam. In your case it could be a collapsed tappet or another valvetrane assy. but it also could be a knock in the lower end, tell me what the miles on the engine are, if it has prety high miles and you have been roding it you could have spun a rod bearing or oggerd the wrist pin out. The thing if you take the pan off you will need to take the front swaybar off and the bad part of it all is to do it right you need to take the whole crank out and replace all the bearings that means pulling the trany out the back of the crank a bit to get the crank to drop out but all in all if you do the whole thing the crank needs turned by the machine shop the most comon is to have it turned to .010 .010 under this meaning the main caps are 10 thousandths under standard and the rods are the same. If you do the whole thing the engine will need a 500 mile brake in period again, but the engine's lower end will be brand new besides the pistons but it will add alot of life. If the wrist pin is bad to check it have the pan off and grab the rods and push them up and down the one that is bad should clunk around.
I am sorry to give all the bad news.

D.Hearne · Mar 15, 2004

If it's a loose pin then it will eventually wear 4 grooves into the cylinder wall. When you suddenly have a milkshake in your oilpan, you'll know what caused it. If it's a spun bearing, it could possibly last a long, long time before the motor goes POOF. I know this is true because one of the 351W's I just acquired, was run until the timing jumped ( no nylon teeth left on the timing gear) This motor also was missing ( yes that's right, MISSING) the #4 rod bearing. The piston top was slapping the bottom side of the head. The motor was run awhile like this, judging from the fact that the journal this rod was riding on was offset ground about 1/16". The rod journal looks almost perfectly normal after all this abuse, shows you the difference in the toughness of forged steel vs cast iron. When you remove the oilpan and inspect the bearing on this "knocking" rod, be prepared to remove the engine too. The crankshaft after taking the abuse from a spun bearing, won't be a pretty sight. Installing a new bearing may buy you a few weeks time but, you'll eventually need to rebuild it, and replace the crank and the offending rod.

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