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Looks best in drag
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Discussion Starter #1 (Edited)
Crank Walk Documentation *mods please move to sticky in technical*

I am documenting my crank walk experience for you guys. I also have questions for you at the end of this thread.

v160
ACT Xtreme
GTE Bottom End

Occured after about two years of driving with this clutch. I tried to get it off the road in time but the last mile home was terrible. I also did not disable the clutch switch like I should have. Boy am I paying for that mistake..






My questions:
1. Aside from the damage to the block in picture two, there isn't much other visible damage to the block. The face of a few mains look a tad banged up. What should I be looking for also on the block? Will an experienced machine shop be able to give me an answer by visually inspecting the block and caps?
2. The crank is a major concern. It's very hard to see any damage on the journals of the crank, but there has to be some. When should I consider replacing it instead of having it fixed?
3. I noticed the rod bearings are a matte light blue. Is this normal or have I experienced actual bluing? The back of the bearings look normal.
4. There were shavings in the pickup. Can I clean it out sufficiently or do I need a new one?
5. After something like this, how trustworthy is even a well-fixed block? I spin this motor to 8600rpms.

I hope we can build on this thread.

Kill
 

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Sorry that I can't answer questions for you really...but if the crank journals have some damage, would it make sense to go with an sp 3.25 stroker motor? The reason I ask is because they machine your crank for the additional stroke. It's basically 6k and may take care of anything that was damaged. I apologize if this is getting off topic.
 

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Been there done that :(

I lost 2 shorblocks in the exact same manner, one on the dyno in
Texas at that! The bottom line is, get a twin or triple. The plates are wayyy lighter, and the discs themselves do the bunt of the work. Every time we put clutches in supra's we disable that switch. A high mileage or hard starting car could die within weeks of installation.

You have to think, the thrust washers are not pressure fed , they simply rely on oil being splashed on them via the counterweight. So when your car hasnt run in a month, every drop of oil is sitting in that pan. For a few seconds, they are bone dry creating some metal/metal contact. Having that heavy plate smash them up against the main cap sure doesnt lessen the impact :)

On our blocks now, our machinist puts a little radial in the main cap , so oil is being squirted at the thrusts when there is pressure.


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Ps: To answer all your questions in one shot: GET A NEW BLOCK & CRANK!! I dont care if someone as reputable as Jim Justice said you could re-use it, fuck that. Call it superstition, but I would never trust that block to be true. Im sure that has caused a gross misalignment in that main cap, and the mains will at least need to be honed. Then you will be using off the shelf bearings, band-aids, etc... Id man up and do the new SB from Elmhurst, and then go through it before putting it in the car. The pickup and pan need to be thoroughly cleaned as well as all the hardware in there.
 

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Cheifbootknocka
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Why would disabling the clutch switch fix this problem ?
 

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Why would disabling the clutch switch fix this problem ?
You're not using the clutch to start the car at the most critical time when oiling is at it's lowest.

Definitely get a new block and crank and multi-disk clutch. I've seen a few cars where they used the existing block and even put a new crank in along with all machine work, only to have the problem happen quite soon.
 

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Instead of totally getting rid of the clutch switch, just move the switch somewhere off of the clutch.
I mounted mine elsewhere, its kind of like a theft deterrent thing of some sort.
sometimes I totally forget about it and I press the clutch and nothing happens then I am like, oh yea.
 

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Cheifbootknocka
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You're not using the clutch to start the car at the most critical time when oiling is at it's lowest
Im still lost. Doesnt the switch just disable the starter ? so if its left in gear and you turn it over it doesnt run into something ?
So regardless of the switch being on or off, the motor is still turning over :scratch:
 

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Im still lost. Doesnt the switch just disable the starter ? so if its left in gear and you turn it over it doesnt run into something ?
So regardless of the switch being on or off, the motor is still turning over :scratch:
You start it in *neutral* with the clutch out so the engine doesn't have the force of the pressure plate pushing it without oil.
 

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Cheifbootknocka
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You start it in *neutral* with the clutch out so the engine doesn't have the force of the pressure plate pushing it without oil.
Ah, gotcha. makes sense now.

Do you guys really attribute crank walk, partially to start-up oil starvation of the thrust bearings?
 

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Ah, gotcha. makes sense now.

Do you guys really attribute crank walk, partially to start-up oil starvation of the thrust bearings?
Its been debated forever. Bypassing the switch certainly won't hurt the situation. Personally I think the high rpm shifts with a heavy PP do the damage (I think the oil between the crank and thrust bearing gets forced out by the pressure of the PP during the shift and, at high rpm, you've got a bunch more time (proportional to the rpm) for the shearing wear/damage to manifest than at idle -kinda similar to high rpm shifts that can oil starve and kill the thrust washer on R-154 transmissions)
 

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Ah, gotcha. makes sense now.

Do you guys really attribute crank walk, partially to start-up oil starvation of the thrust bearings?
Of course, we've seen guys crankwalk a motor while it was cranking right after a clutch install without the clutch bypass. If that doesn't contribute, then what else would...
 

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Cheifbootknocka
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Its been debated forever. Bypassing the switch certainly won't hurt the situation. Personally I think the high rpm shifts with a heavy PP do the damage (I think the oil between the crank and thrust bearing gets forced out by the pressure of the PP during the shift and, at high rpm, you've got a bunch more time (proportional to the rpm) for the shearing wear/damage to manifest than at idle -kinda similar to high rpm shifts that can oil starve and kill the thrust washer on R-154 transmissions)
Sounds logical. I would like to know if there are any documented cases of crank walk on motors with auto trans.
 

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Of course, we've seen guys crankwalk a motor while it was cranking right after a clutch install without the clutch bypass. If that doesn't contribute, then what else would...
good to know! I'm curious at what pressure does a PP become dangerous for the thrust bearings.
 

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Looks best in drag
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Discussion Starter #18
I would assume anything greater than a stock pressure plate, as its heavier than designed. I know this is because I didn't disable the switch.

Kill
 

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Ps: To answer all your questions in one shot: GET A NEW BLOCK & CRANK!! I dont care if someone as reputable as Jim Justice said you could re-use it, fuck that. Call it superstition, but I would never trust that block to be true. Im sure that has caused a gross misalignment in that main cap, and the mains will at least need to be honed. Then you will be using off the shelf bearings, band-aids, etc... Id man up and do the new SB from Elmhurst, and then go through it before putting it in the car. The pickup and pan need to be thoroughly cleaned as well as all the hardware in there.

Agreed, reusing a walked block/crank is asking for problems down the road.
 
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