Does this THRUST BEARING look ok to you?
 

Everything looks great inside the engine. I pulled a couple of mains to make sure the bearings looked ok.
Yes, the clearence was checked when the engine was assembled.
I just do not want to close it back up if this is a possible problem in the future.

Re: Does this THRUST BEARING look ok to you?
 

Not totally uncommon for a BBC thrust bearing to have a little coating missing on the thrust faces. there does not appear to be any deep scoring or burn marks, however its only appearing on one face so it idicates a little thrust in that direction. You should re-install and make sure the crank has about 5-7 thou thrust clearance fore and aft, use a soft mallet to force it fore and aft for checking. The one sided wear indicates some overage possibly in that direction from something not quite aligned correctly or creating some over thrust.The thing that bothers me from your picture is the wear pattern on the bearing journal surface. It seems a bit uneven as though the main bores may not be correctly round, out of alignment, or maybe just a bit to much clearance on the mains. Hard to tell everything here from just a picture, but I would get a local engine expert to have a look before you button everything back up. You guys might also consider using the new "alumina" series bearings instead of the old 77 series. We are finding we can run tighter clearances, have better bearing life and see a lot better condition on the crank journals from high loads. I really like these new bearings. Just my two cents.

Ray @ Raylar

Re: Does this THRUST BEARING look ok to you?
 

Just checked the end play.
.020 :(

Re: Does this THRUST BEARING look ok to you?
 

thats ugly
:(

Re: Does this THRUST BEARING look ok to you?
 

If the end play is that big now from wear on the thrust face on the bearing, somethings wrong here. Looking at the picture again looks like the thrust wear is coming from the drive side. I am guessing there's a problem in the coupler, shaft or drive gimbal bearing that's putting too much pressure on the crank flywheel hub side. Put in a new bearing and measure the same clearance again as a check. If its where it should be, then your wear is happening and the cause should be found and fixed before this combo goes back together.

Ray @ Raylar

Re: Does this THRUST BEARING look ok to you?
 

Ray whats the new alumina bearings ya taking about???


By load do mean like over 600HP?

Re: Does this THRUST BEARING look ok to you?
 

Most of the big bearing manufacturers, Clevite, Federal Mogul, King, etc are mandated to stop using lead in their bearing compounds. After researching for new bearing compounds they have in the last 5 or 6 years started using an alumina/silca oxide material in the top coating on the bearings versus the old tri-metal type bearing buildup. This new material has already proven such a great improvement that most of the big automotive manufacturers have been using it as the bearing of choice for most of the new engines. Some of the benefits of this new bearing technology is much better durability and bearing life, an actual micropolishing of crankshaft journals in the engine when running, a better oil film retention under loads some of which is due to the microscopic surface makeup of this material after application and also this bearing surface does not have a tendency to imbed dirt, metals and solid contaminats in the bearing surface, but tends to spit them out where they are not imbeded to cause crankshaft journal gouging and wear.
When we tear down motors specifically the 496 engines we always seem to see excellent bearing surfaces that sometimes look better than they did on initial assembly. We also feel that we can run slightly tighter bearing clearances on these bearings in our normally aspirated motors which we feel is a benefit for controlling oil throw off and pressure drop with today's better oils. Raylar thinks this is one instance where a enviromental issue solution actually worked to the benefit of todays engines. You might want to start investigating the use of these bearings in marine high performance engines and what we feel are some serious benefits!

Ray @ Raylar

Re: Does this THRUST BEARING look ok to you?
 

Thanks for the info. It looks like we prob don't have a choice when they quite using lead?

Ray So your saying you still would run a looser clearance in a blown apli with the new aluin bearing???

Re: Does this THRUST BEARING look ok to you?
 

I installed a new thrust bearing this morning and that put it back into specs at .006.
Ray you said there might be a problem in the coupler, shaft or drive gimbal bearing that's putting too much pressure on the crank flywheel hub side.
What would I look for next?
Everytime I put the engine back in the alignment tool slides right in no problemo.
Nothing has changed in those areas for as long as I know of.
I am going into unchartered waters :eek:
The only thing I can think of is when I first started this engine last year it vibrated so bad it about came out of the boat.
(no dowl pin on flywheel and I put it on wrong)
But I only ran the boat for 5 minutes tops while I was scratching my head.
Could something that simple cause this problem.
I ran the boat over 100 hours last season with no problems at all.
JIM

Re: Does this THRUST BEARING look ok to you?
 

Jim, I am definitly not a drive expert or alignment Guru but I am sure there are a few good ones here on OSO who might chime in and give you some things to look for. I dont think that 5 minute rumble took off .014" metal though, chances are this is a 100 hour wear issue. The only thing I have seen was a drive input shaft that was pushing on a crankshaft input area when the drive was bolted in place and obviously did not have enough fore -aft clearance and the pressure was wearing a thrust face something similar to your situation. I am sure there may be other possible causes, but again I will leave those ideas to the experts. Calling all drive experts, Jim needs some input!!

Ray @ Raylar