Cylinder wall condition, should I be worried?

[Dragon Humper]

If a torque plate was used they should have asked for the headgasket and head fasteners to attach the plate. Some shops bolt on everything else, like motor mounts and such, to be certain the bores are completely distorted.

Ok, that's a little out of control. Your fasteners won't do anything anyway, most torque plates are only 2" thick. The motor mounts and such don't distort the bores at all, they don't even do that on 2000hp turbo motors from Nelson Racing and the like, why would they do that on a 600hp passenger car motor. I think anyone that is going to that extent is only hosing you for more shop time. You can do 90% of what a torque plate will do with just screwing some short fasteners into the deck. I and several local dudes working with our local machine shop have confirmed this over the years.

He already said the pistons looked good so it can't be a piston to bore issue (please get back to us with the measurements), has to be rings butting or garbage getting caught up in the rings.





Jon.

[Blackcossie]

Ok, that's a little out of control. Your fasteners won't do anything anyway, most torque plates are only 2" thick.

http://www.turbomagazine.com/tech/turp_0809_nissan_ka24de_build_machine_shop/photo_07.html

A proper torque plate will come with spacers to simulate the exact height of the cylinder head, it is also important to use the exact headgasket that will be used in final assembly.

The motor mounts and such don't distort the bores at all, they don't even do that on 2000hp turbo motors from Nelson Racing and the like, why would they do that on a 600hp passenger car motor. I think anyone that is going to that extent is only hosing you for more shop time.

http://www.goodson.com/blog/2012/01/13/cylinder-boring-tips/

Too many variables to comment directly on this, the engines you refer to from nelson may be purpose built drag motors that don't use motor mounts and have little to nothing bolted directly to the block. The point is to imitate the engines final state at the time of machining, I would expect 95% percent of local engine builders do not do this but I guarantee you it is regular practice at high end engine builders and if you're worried about the cost of bolting on a set of motor mounts then you have no business building a high end RB. Try pricing out the cost of hot boring an engine.

You can do 90% of what a torque plate will do with just screwing some short fasteners into the deck. I and several local dudes working with our local machine shop have confirmed this over the years.

Seriously?

He already said the pistons looked good so it can't be a piston to bore issue (please get back to us with the measurements), has to be rings butting or garbage getting caught up in the rings.

Pretty sure the pistons are still in the motor and have not been inspected. I have experienced every failure you can imagine in the almost 20 years I have been building high performance engines. Typically when ring gap is too tight, the ring will either break or stop rotating and cause a score mark that runs from the top to the bottom of the stroke on the cylinder wall. If it was foreign debris in the cylinder, damage tends to be up high and is random. The damage in the pictures posted is consistent with improper clearance issues I have experienced first hand, the damage is inline with the skirts of the pistons and is low in the bore.

[Blackcossie]

Anyway, I would say the OP's damage is minor and a hone during reassembly is about all that can be done with his current components. Compression is good so I would assume the rings will show no damage and can be reused if sourcing new ones are an issue.

[Dragon Humper]

And his damage travels up to the top of where the ring lands would be.........


Awaiting for updates.......



Jon.

[gezed]

found the problem, posted on OP, most likely shavings from thrust bearing got into the oil and caused the marks on the walls

[Blackcossie]

found the problem, posted on OP, most likely shavings from thrust bearing got into the oil and caused the marks on the walls

Oil filter should have caught any debris from your bearing issue and bearing material is pretty soft compared to the piston and cylinder wall. Have you removed the pistons yet? What does the skirt look like? I personally have never had this type of damage with bearing failure.

[Dragon Humper]

The oil filter won't catch debris that is being flung around the crank case by the crank throws. As he said before in a previous post, the piston skirts looked good save for a few that were slightly scuffed.

Do you remember what the end play was on the crank when you put it together? I have seen a fair more than normal RB thrusts that have wiped out over other engines. Is there some oil gallery hole on that main that really needs to be paid attention too? I have seen thrusts on the flywheel side wipe out on this forum over the years even with stock clutches, sounds like a problem area.

If all else fails you can shave a bevel (front to rear) into the parting line of that bearing progressing from shallow to what you want for a gap on the trailing side of the bearing. That will give you more oil to the thrust on the rear without compromising the oil pressure needed for that bearing surface. That trick has been around for a looong time.




Jon.