401 Rebuild Help

[Lifted79CJ7]

Thanks, That is kinda what I thought. As for the cam bearing, there is one side near the top that was a little more worn than the rest, but not by much. The rod bearings were toast. They have definitely seen better days. I am still confused, cause I cannot tell what was making the loud knocking noise. I can spin the crank free by hand and don't here any grinding, but that is all thats left. Any idea where to look? The noise would come and go, come and go, then it just stayed there.

This was all during the cam break in cycle, whch lasted about 20 minutes. I did find in the oil pick up screen what looked like a blade of grass made out of metal. If I can find it tomorrow, I will take a pic. Lord knows where it came from.

OK, so I am gonna call the machine shop tomorrow. What all questions do you guys like to ask to see if they know there stuff or not? I really don't want someone screwing the pooch with this block or crank. I need all the normal stuff done, plus I am gonna get them to install the oil bypass kit to allow better oiling to the rear of the block.

Thanks!
Jack

[Rocky]

Lots of stuff that could cause a knocking sound: bad rod bearings/journals, bad mains/journals/ bad wrist pins. I've also seen broken cranks that caused a knocking sound. Although broken clean through, the mains hold the two pieces of crank in close enough proximity that the engine continues functioning, until the mains finally go, the knocking gets louder, and the whole thing finally comes apart. (I've pulled 'em apart before total destruction, to find everything seemingly right in place... no crack even visible in the crank until pulling the main caps... then it falls apart!)

The cam bearing wear in your photos is fairly advanced. (Are those strips of bearing metal in the shot? ..Your "blade of grass" could be a strip of bearing metal, forced out by overheating and friction.)
The rod bearing wear is pretty bad, and there appear to be some pretty good grooves on the one journal you show.
The wear on the pistons isn't abnormal, from what I can see. Don't jump at boring it until you have it mic'ed. If it doesn't need boring, you'll give yourself the possibility of one extra rebuild on the block if you just hone it and put new pistons in.
Nothing wrong with ring gap... it allows expansion. Remember that the ring gap on new rings will measure out at only a couple of thousandths, and will be less than that w/ expansion. Be sure to measure your ring gap (w/ rings square in their respective bores) and file/fit the rings, if necessary.

[Holeshot]

IS it a rod knocking, or is it a cracked vibration damper????

I got a '71 401 from a salvage yard and darn thing seemed to have a rod knocking. Yanked it out and tore it down. Looked good - except for the crack in the vibration damper, right at he keyway slot.

[Lifted79CJ7]

That is a good one on the Vibration Dampner. I have never heard of that one, but no, it was OK. As for the knock, it would just come and go like a light switch going off and on. I think if might hve been that nail I foooound in the piston, or could have been something else. Not sure yet. IT defineitly wasn't like a normal bearing going south where the noise gets louder and louder. It wasn;t there, then it was, then gone again, then would return. Then it was there for good. Oh well. I will figure it out!

On another note, just talked with the machine shop today to get some quotes (haven't been out there yet to check it out, but the guy knew his stuff and has done a some 401's), here's what he rattled off to me rather quickly. How do these sound to you guys?

Hot Tank Block and Heads $45 Sounds ok to me
boring and honing: $Crap, didn't write down Doh!
Install new freeze plugs: $75 You have to be kidding me
Press old pistons off and new ones on: $80 Maybe Mud can help me???
New piston studs: $120 Forgot what all he was talking about here
Deck the block(depending on what needs to be done): Up to $175
Regrind the crank (if needed): $120
Align hone the block (if needed): $175
3 angle vavle job (magna flux and light mil work): $300 Ouch!
Balancing Rotating Assembly: $150 A little high, but doable
Rod work to accept Chevy full float pins: $180 If using KB pistons-ouch!

Of course some of this stuff I can do myself, but overall, sounds like a lot of moo-la to me. I will need to swing by after doing some more homework and talk with him in more detail about each step and see what will actually need to be done. Overall, this guy knew his stuff though.
Anything left out or think I can do myself?
Jack

[ILUV2XLR8]

Some of those quotes sound pretty steep, I pulled the reciepts from my last build here's what I paid:

Bore .030 = $96
Grind C/S .010R .010M = $90
Magnaflux Block & Clean = $20
Balance Rotating Assy = $185
Mount Pistons on Rods = $40
Install Cam Bearings = $25

My block was within tolerances, so I didn't line hone or deck it.

[Elliott]

That is a good one on the Vibration Dampner. I have never heard of that one, but no, it was OK. As for the knock, it would just come and go like a light switch going off and on. I think if might hve been that nail I foooound in the piston, or could have been something else. Not sure yet. IT defineitly wasn't like a normal bearing going south where the noise gets louder and louder. It wasn;t there, then it was, then gone again, then would return. Then it was there for good. Oh well. I will figure it out!
Jack

Have the crankshaft endplay checked out, may of had slop.

[Gremlin4ever]

Also check the flexplate if it is an automatic (they crack as well and makes a knocking sound) didn't see anywhere as to which type trans your running prolly standard in a CJ.

The best tool you can have for a rebuild are: "Engine Builder's Handbook" or "Guide to Engine Blueprinting" in my opinion They can be had for under $20 each at you local book store.







post #2