Final days of the 401 on the dyno

[Goose]

How many hours on the motor?

[Blown7]

5-7 hours just dyno time. Hard to be specific about.


Jeff

[Goose]

That supports my theory.. Most of the wear an engine experiences happens in the first 500 miles..after that (everything else being good) the wear is very slow. bearings etc .. I guess this may be one of those duhh yea we knew that kind of moments.. But I always felt that guys who swear by "tight" engines really didnt understand that by the time its "broken in" It's no tighter really than one built looser..

What do I know though.. I have 2 crescent wrenches (AKA Speedwrench) and twelve hammers in my toolbox.. And an unhealthy fascination with acetylene.

[1980_Cj7]

Wow, and I thought our bearings looked bad after only 300 miles. Of course we weren't making the kind of power Jeff is, and also had detonation problems from the machine shop installing the timing gear wrong.

[jeepsr4ever]

It almost looks like crank flex Jeff. I see what may appear to be chatter on one of the thrust bearings. It looks like you knicked the crank with a rod bolt on one of the rod bearings. I would also add that your oil viscosity looks to be too high for the bearing clearances. I also think the bearings that show the pitting could have been poorly plated.

[82Waggy]

MC, Do you think the pitting is from poor plating? Looks to me like he just had a bunch of grit that got embedded - maybe babit material that got knocked loose by dirt.

Also looks like the crank was draggin around some debris or a burr on the crank that got into the copper - maybe from a poorly chamfered hole in the bearings or crank.

I don't think the bearings themselves are faulty.

Clean that sucker, install new bearings, and go again!

[jeepsr4ever]

It was either dirt or a knick from installing the rods. I am going with the dirt theory. Check your end play Jeff

[Blown7]

It was either dirt or a knick from installing the rods. I am going with the dirt theory. Check your end play Jeff

Yep MC it was dirt, or more specifically cast iron. I actually inspected the bearings with a high power magnifying glass and found cast iron specks. I did alot of drilling on the oil galley passages. And I cleaned the passages to what I thought was spotless, obviously I did get it clean enough. It almost impossible to nick a crank with the Carillo rods as the bolts are not part of the beam assembly. If you did nick the journals which I did inspect one would find a straight line across the journal like a chisel mark from the bearing parting line. The bolts go on thru the cap side at assembly. I think some crank flex was happening as this is about all the horsepower the stock crank can handle. I definately think I am at the horsepower limits of the engine.
As for one bearing loosing the plating I think the cast iron chips and a combination of substandard Clevite plating caused it.

I wish that some vendor would step up with some high performance AMC engine bearings.
Clevite offers several grades of bearings for other engine applications but only one grade for AMC's.

Heres a some pics of Carillo parts.








And then the thought of the bearing clearances being set up for the viscosity of 20 weight oil using the Machinerys Handbook.
Check out the section on Journal bearings MC. interesting info there.

So I'm still researching bearing options I was talking to someone that said Federal-Mongol was making them.



Jeff

[Goose]

You know.. I have read the concept of crank flex in this thread.. but you know I just read right over it and didnt think about it, till just now.. Crank Flex??? yikes.. thats enough to scare the wadding out of ya..(I mean if ya think about what happens when that crank decides to stop flexing and break...

[82Waggy]

I don't think there is a bearing made that will endure having iron filings ground through them. Clevite bearings are used on a lot of high powered stuff without problems - I don't think they are at fault here.

I think Federal Mogul and Clevite bearings are the same part these days.

As far as I have been able to find, AMC bearing makers include Clevite, ACL, and King. Don't know if there is much significant difference between them, aside from the ACL's being the full groove type.