new build and it walked

[TOONAH]

Jeremy,
First off I am sorry this happened to you. But I have just built a 7 bolt with a new Topline Crank. I had it inspected by a very excellent machinist (who did my block work). He said it checked out fine. I had him farm out the block to another machinist who "aligned honed" the mains with torque plate. I used ARP mains studs. I got the motor fired up. Good oil pressure, even with only base tuning the bi*** really roared! However, during the leak inspection phase, I discovered coolant blowing into the down pipe. Eventually discovered a pinhole leak in an exhaust port valve 'bowl'. I paid $2500 to a guy to have my 1G head CNC ported.
Anyhow, back to your thrust bearing scenario. Please answer me these three questions and I'll re-post my opinion on what caused your problem.
1. Which side of the thrust bearing failed? The side facing crank pulley or the side facing the clutch?
2. the thrust side that is chewed up; does it look flattened? Is the height of the thrust increased. Kind of looks that way in your photo.
3. Exactly what clutch were you using and did you do any "launching"? Letting the clutch out at 3.5K rpm's or there abouts?
Look forward to your reply.

 

[jeremy19984g63]

1. clutch side.
2. height not increased, just chewed away.
3. no launches, just babied. act 2600. clutch switch disabled

 

[TOONAH]

I should have asked was the thrust part of the bearing flattened?
In the 6 bolt thrust bearing pics that MidShipCivic posted in this thread, you can clearly see that the flywheel thrust part of the bearing is 'flattened'. In the 7 bolt motor that I tore down the TB's look almost identical except that the motor was still running (broke timing belt). Like I said there was close to 0.075" of endplay. But that motor had 173 thousand miles on it. Well being the detective I am when it comes to troubleshooting electro/mechanical failures, I do my research first. I have read everything possible on PREMATURE thrust bearing failure and not even Magnus's exhaustive analysis satisfied me.
Even your TB's look like they got "mashed". I notice also that they are not the ACL Race Bearings. ACL race bearings do not have the final 'sintered' hard shell layer applied. They first thing I noticed in my 173K mile motor was all the little bits of this silvery 'sintered' metal still in the oil on the inside bearing journal mating surfaces. I could see that these bits had chewed furrows into the bearing surfaces.
So your bearings have the sintered layer. I chose the ACL Race bearings because I believe this 'sintered' layer is PART of the root cause of premature thrust bearing failure.
Now, one has to ask one's self, why does the 'sintered' layer come off?
My guess is that (this is hard to describe, drawings would help) if the thrust walls on the crankshaft are not exactly 90 degrees to the center boreline of the crank and the thrust bearing walls on the bearing are not exactly 90 degrees to the crank walls, then the two will not mate evenly. Try to see in your minds eye, the crank thrust wall spinning around. If alignment of crank/bearing walls is off by even aa few thous, then there will be a noticable 'wobble' there.
When the clutch is let out and the friction disk is shoved against the flywheel, the bearing thrust wall (facing flywheel) is slammed by the thrust wall on the crank. Well, because of the wobble, due to misalignment of crank, the bearing thrust wall is distorted and the sintered layer cracks and flakes off. The bits of sintered material immediately chew up the crank thrust wall. If there was 0.004" endplay to start, you probably would get another 0.005' endplay very fast (a few miles). That is what happened to your bearings. But I forgot to ask. Did you find some silvery flakes on the crank thrust wall?
What else could have gotten in there to chew them up like that?
So, in final conclusion I believe the ROOT cause of "Crankwalk", aka Premature Thrust Bearing Failure
is MISALIGNMENT of the crankshaft. It is a design flaw in the one piece main caps girdle. Even though the idea was to strengthen the block design, so that the horizontal and vertical plane torsional stressors
would be contained at higher power levels, the ability to properly align the 'girdle' during assembly was a mystery, even to the factory that made the bloody things. I have built (sucessfully) all manner of motors up to 1200 HP and I tested them on dynes.
It has to be the one piece cap design. Now of course not all 7 bolts died of premature thrust bearing failure. But a lot did, right out of the factory.
The sintered layer accelerates the failure. But it is the mains bore alignment referenced to the crank center bore alignment that is critical. Some people claim that "alignment dowels" help prevent the girdle from shifting. But if the crank is not machined true to within 0.0001" (One ten thousandth) and the girdle thrust wall does not mate to within 0.0001" of its other half (in the block) then the thrust wall on the bearing will be distorted enough to chew the sintered layer right off.
Well, let me know what you think.

 

[donniekak]

It is very clear by the wear on the bearing that the thrust surface of the journal is not square with the crank centerline. All a line hone does is make the journals the same size and line up the bores. There is no operation to square up the thrust surface for us because there are no oversized thrust bearings. This is the heart of 7 bolt crankwalk, and why a block that walks walks again, and some blocks are fine. The machining of the thrust surface is not consistantly good.

 

[Strm Trpr]

I agree with TOONAH.

Like mentioned above, align honing the mains simply aligns all 5 main axes to one another while sizing them.

Anyone know how a race engine machine shop align hones the mains to be perpendicular to the thrust surfaces to be within .0002"?

Removing material from the thrust surfaces is not an option as stated above.
So how do they align the main bores to be perpendicular to the thrust faces in the block?

Here's a good read.
http://www.circletrack.com/techarticles/ctrp_0701_engine_block_prep/index.html

So far it doesn't mention anything about the thrust surfaces inside the block.

 

[motomattxxx]

My opinion is that the 7bolt main bearing towers actually FLEX when a heavy clutch pressure plate is used, if you look at the one piece girdle design it does'nt have the lateral support that the 6bolt does. Again this causes misalignment between the crankshaft and main towers, this has been a LONG standing theory of mine.

 

[rbwtrans]

I also noticed that you posted that the mains were line honed using a torque plate on the block. Was your head installed when you torqued the mains? If not then the block distortion caused by the torque plate during the honing process could actually cause the mains to be mis-aligned if they were torqued down without the same same amount of forced being applied to the upper end of the block. That's exactly why torque plates are used... to be sure the block distortion is present( as it would be assembled with torque applied) while being machined. I'm going to jump on the bandwagon with main mis-alignment. Good luck. I hope that you find a solution to your problems.

 

[Strm Trpr]

Here's some additional information.
Thrust bearing failures

This is even most interesting and I took it from the last paragraph from the above link.

Other External Problems. Aside from the items already mentioned, there is another external problem that should be considered. Inadequate electrical grounds have been known to exacerbate thrust surface wear. Excessive current in the vehicle drive train can damage the thrust surface. It affects the thrust bearing as though the thrust surface on the crankshaft is not finished properly finished (too rough). Excessive voltage in the drive train can be checked very easily. With the negative lead of a DVOM connected to the negative post of the vehicle battery and the positive lead on the transmission, there should be no more than .01 volts registering on the meter while the starter is turning over the engine. For an accurate test, the starter must operate for a minimum of four seconds without the engine starting. It is suggested to disable the ignition system before attempting this test. If the voltage reading observed is found to be excessive, add and/or replace negative ground straps from the engine to the vehicle frame and transmission to frame until the observed voltage is .01 volts or less. Note: Some systems may show a reading of .03volts momentarily but yet not exhibit a problem. For added assurance, it is a good idea to enhance the drive train grounding with larger battery cables or additional ground straps.

 

[motomattxxx]

^^^ I like it. I am going to invent a sacrificial anode for the dsm, .

 

[red_devil]

So its very important to get the block align-honed, especially 7 bolts.

 

[jonjon8585]

So its very important to get the block align-honed, especially 7 bolts.

It is very clear by the wear on the bearing that the thrust surface of the journal is not square with the crank centerline. All a line hone does is make the journals the same size and line up the bores. There is no operation to square up the thrust surface for us because there are no oversized thrust bearings. This is the heart of 7 bolt crankwalk, and why a block that walks walks again, and some blocks are fine. The machining of the thrust surface is not consistantly good.

im a noob and all but

 

[red_devil]

im a noob and all but

Sometimes I cant read


Does anyone know if some 6 bolt guys with the Kiggy main gurdle have any issues? or were the blocks moslty built to spec?

 

[untouchablecc]

I might be a hair off the reservation here but aren't some people running NT 6 bolt blocks without oil squirters and running the hell out of them an there holding up just fine. I know this is a seven bolt but is the difference that vast?

 

[GSTTOBEAT]

EVO3 is a 7 bolt there bud

I am aware that the EVO3 is a 7 bolt.

 

[motomattxxx]

I might be a hair off the reservation here but aren't some people running NT 6 bolt blocks without oil squirters and running the hell out of them an there holding up just fine. I know this is a seven bolt but is the difference that vast?

Your correct, but I dont see what you are comparing here, apples to oranges. The 6 bolt 4g63 n/t and 6 bolt 4g63t are the same casting, one has the holes drilled and tapped the other has them but not drilled and tapped.