Well, I pulled apart the 150 mile old 406. As expected the crank thrust surface was shot. The bearings are junked up with minute metal bits. Changing the crank, and all bearings was expected. I will even change the cam bearings that survived quite well. No sense in leaving them in. Popping the cam bearings out will let me spit shine the block and have it super clean. The surprising damage was to the crower cam. I used the springs and pressures recommended on the cam card. The wheels of the lifter seemed to have brindelled the cam. Of course Crower is kind enough to sell me a new one. Has anyone had this happen? This is very new to me. I have run many hydraulic rollers and have always had good success. The 406 is gonna have to wait. My work has dropped to 2 days a week (on a good week) and food is more important than 406 rebuilds. I have enough stuff laying around to throw a stout 383 together for less than $200 . Sure am glad I am a pack rat!

 

Hey Pete,
I've been on vacation and missed your post? What the hell happend to that new 406?

 

Dupe

 

No, never had that happen. How about some more info though.

When exactly did the problem surface? At what rpm, etc.?

What was the thrust clearance when you put it together?

Auto or manual trans? If auto, there wasn't bushing in the crank was there?

Was your block checked before you put it together?

Were you using a thrust button/bearing and Torrington bearing on the cam?

Before I'd begin a rebuild, I'd try to find out what caused the failure. No need to do a rebuild and have the same thing happen all over again.

Jake

 

I agree that a cause needs to be found. I am reasonably sure that the cam issue is a seperate one from the crank. The cam was installed with a comp cams 210 (stiff azz) timing cove and a roller button. Endplay was .005 or so. The cam gear was machined (by Cloyes) for the torrington that they supplied. No expense was spared in the valvetrain.Block was done to the hilt. Bore,hone, square deck, torque plates, line hone etc. Crank had .006 endplay when assembled. In 150 miles it grew to .015-.016. I discovered the problem when I heard the starter gear touching the flexplate at idle. Sure sux. I am hoping that the crank was a poorly repaired reman. This or a defective bearing (highly unlikely)

 

I forgot to mention. Auto trans and I reused the torque converter that came out of my hurt 383. That motor went together with .003 endplay. Was still .003 after 10 rough years.

 

what did the cam bearing (the torrington cam button) look like when you pulled out the cam? Was it still in one piece or broken?

I've heard those tend to grenade after a while and, of course, FUBAR everything else with it's bits.

 

Unfortunately that was perfect. The cam looks like it was made soft enough for the lifter wheels to dent the cam. This even occured on the base circle of the lobe. Not massive damage but enough to feel. The crank problem really has me wondering though. How thrust on the crank can grow .010 in 150 miles is tough to figure. Both the crank and bearing are severly gouged. Both were perfect before install. Damage is too sever to figure which of the 2 were the root cause. Both are going in the trash though.

 

Keep us posted if you find what caused this. The cam problem sounds very abnormal. Hope the 383 goes together well.

 

Pete...

Not sure what to say about what happened. But I would check the block (which is not going to be real easy to do) before using it again.

The 400 blocks experienced many problem - that could possibly be related to the problems you are experiencing. Perhaps a subtle core shift is mis-aligning something and causing problems...???

On a good note, I got your chip replacement for the one your wife threw away and the new one is on its way back to you. Got it out the next day for you.

Proceed with caution with that block thou - I would maybe even opt to get a new dart block if you can swing the $$ to make sure its not something block related. Or perhaps have a different machine shop check the other guys work. You know if you take it back to the original - he is not going to tell you that it was perhaps machined wrong.....

 

Dude, I've had three soft roller cams come through my shop in the last month and a half; two were from Cam Motion and the other was a Crower... Billet pieces but with really crappy heat treating. One of the Cam Motions was so bad the lifter ate through the heat-treating and into the soft stuff... This was on a 406 SB2 motor; and those cams are about 700 bones!!! The one Cam Motion was ruined the other two cams were able to be cleaned up and we re-heattreated them and then cryoed them. Hopefully that'll be okay. I don't know what their problems are, it's not hard to correctly heat treat something.

I would carefully check that block for core shift; that could certainly cause your changing clearances. Additionally when you checked the thrust, did you whack the crank snout and then hub a couple of times while you were tightening the mains? That will "seat" the thrust and give you a more accurate reading; you don't have to do it hard, I use either a brass or nylon 1lb mallet. Just a couple of mild whacks on both ends is all you need.
-Jeb

 

Yepper...gotta do the whack trick.

Won't tell you what I use on mine :o Ahhh what the hell - last time it was an old 4x4 piece of treated lumber about 6ft long. Just some little love taps and the crank loosens up real nice and turns with little effort. Mine only had one small tight spot, which tight is the wrong term. Dads had none, you would whip it and it would turn about 4 times on it own.

My thoughts are of the crank and everything checked out, then it has something to do with the block.

Can you post some pictures of your bearing all laid out in order and both sides....

I would study them to see if they can shed some light....take them to "the different" machine shop and they too should be able to tell you what was likely the cause.

 

Sorry to hear about your soft cams. I only had $425 in mine. That was enough to hurt though. I posted earlier that the lifters (also Crower) were missing the plunger springs. My experience with Crower has been terrible. 10 years ago I had problems with them, and only them, so I gave them another shot. Sorry I did. I think the replacement will be comp cams. I did seat the thrust bearing as you describe. I really crossed the t's and dotted the I's on this motor. I do appreciate the suggestions and I will explore every one passed on to me. I will not sleep well till I find the problem. I do not believe in rebuilding and trying again. My friend owns a dyno and the motor will be run on it, even if I just quickly carburate it for the dyno runs. He will do this for free. Talk about a good guy!
Jesse, You saved a marriage by helping out with my problem. Work has been very slow and my wife does not believe that someone would re-burn a chip for a new motor at no charge to me. I suspect that she saw my chip in the envelope with your return adress and postmark. Then I think she tossed it out of anger. She will not admit it though. She thinks I paid you again. Regardless, I very much appreciate what you did.
Also, I do wish to re-do the 406 the right way using quality parts when the budget allows. Too busy buying gasoline though.
Thanks again for all sugestions and please keep them coming.

 

Here are some other thoughts.

When bolting up the converter was there a gap between the flex plate and the conveter lugs causing you to have to move the converter forward?

If you did, did the lugs then fit flat against the flexplate with NO gap?

I'm asking because if you had to pull the flex plate and converter together with bolts, this could have loaded the thrust bearing.

Does one end of the thrust bearing surface seem to show more wear than the other?

No chance a bushing was left in the crank, right?

No chance the flexplate was installed with the converter mounting pads facing forward rather than rearward, right?

Just trying to eliminate some of the things that may have caused the failure.

In dealing with tight spots, one trick I do is to use only my fingers to run each main cap bolt down until it's flush with the main cap. If I can't turn the bolt with my fingers, I know the cap is cocked a tad.

So I tap on the cap to adjust the alignment and by doing that for all the main cap bolts, I'm eventually able to install all of them using only my fingers. I believe installing them that way insures correct cap index and alignment with the registers in the block and no tight spots result. I don't move to a ratchet or torque wrench until I have run down all the bolts with my fingers, finger tight.

Then when torquing the mains (I use five incremetal steps) at the end of each interval, I rotate the crank by hand, feeling for any tight spot. If, in the unlikely event, I feel any, I back off the setting and have at it again.

I save the torque setting on the rear main until after I've aligned the thrust surfaces of the bearing and crank (the ole' wacko with a hammer maneuver) and have torqued all the other main caps in place.

I'll bet you do much the same, but for the benefit of others following this thread they may help.

Just some of my thoughts; hope they're accepted in the vein intended.

Jake

 

Jake, I appreciate the tips. I did run out to the garage and recheck the rear of the crank for bushing. It is not there. I also checked the flexplate as suggested. I did install it correctly and it fit flush like a glove. In my younger days I did make the mistake of drawing in the torque converter with the bolts. I ruined a trans and leared that lesson well . Now I lower motor in mounts and recheck the converters able to spin free and can be pulled foward into the crank. All advice is welcome and appreciated. I am a bit humbled by this. I have built over 2 dozen motors with great success. This failure is a big kick in my ego.

 

Dude, it happens... Don't beat yourself up over it. I ran a high end machine shop and EVERYONE makes mistakes. I ate a large amount of a 555" Big Duke motor one time because of a shop mistake. It happens, just recover from it and learn not to do whatever you didn't do (or did wrong) the next time.
-Jeb