Dropped my crank!

[87witmoreboost]

To all who have experience with this or work with bottom ends FREQUENTLY:

I took my motor apart last week and have had my crank sitting in my block since, no main caps.

A friend came over tonight and I rotated my stand (!!!) forgetting the crank was just resting, and it fell. It fell about two feet to my garage floor. None of the journal surfaces touched, aside from the rear main seal surface.

This is the bad scratch - I think it's on the other side of the seal but feel free to give your 2 cents:

The next here is the dent that occurred on the seal surface. It takes up about half of the seal surface, so I don't know if it's a deal breaker or not. It is right on the red mark (the color of my engine stand, dur)

Aside from surface defects, would this instantly bend the crank? What are my options? I can give it to a machine shop to check it, but if I need another I assume it's better to buy a used crank? But the that has to be checked and maybe ground/machined.

I'd really appreciate some feedback from someone with experience and not just "I heard".

 

[dumbo]

When I was in school the group beside me dropped there cam and crank about 4 feet of a cart. Amazinly the BOTH "V" blocked ok, they were out of a Detroit 4 banger though, bit more beefy. Get it v blocked at a machine shop and just hold your breath. As for the seal surface, it'd have to see it in person to make a call. Good luck dude...won't do that again.

 

[Suprapowaz!(2)]

Our cranks are forged steel cranks. Would it really do any damage internally by dropping it two feet??

 

[87witmoreboost]

When I was in school the group beside me dropped there cam and crank about 4 feet of a cart. Amazinly the BOTH "V" blocked ok, they were out of a Detroit 4 banger though, bit more beefy. Get it v blocked at a machine shop and just hold your breath. As for the seal surface, it'd have to see it in person to make a call. Good luck dude...won't do that again.

I will be v-blockin tomorrow. In either case, i'll talk to the machinest and get an opinion. I bet having it checked by him would be pricey, but i'll look at all options. I wouldn't fret over it but too many people say to not even store it without hanging it or supporting by the bearings so I would think a drop would be pretty bad.

Calling all builders...

IJ?

 

[dumbo]

I will be v-blockin tomorrow. In either case, i'll talk to the machinest and get an opinion. I bet having it checked by him would be pricey, but i'll look at all options. I wouldn't fret over it but too many people say to not even store it without hanging it or supporting by the bearings so I would think a drop would be pretty bad.

Calling all builders...

IJ?

It shouldn't be pricey if he's a decent guy, maybe charge you one hour shop rate. If he feels for you a nice guy would do it for free. As long as he has V blocks, and a dial indicator.

http://cygnusx1.net/supra/Library/TSRM/MK3/manual.aspx?S=EM&P=83


I'm sure you've read that, but I'm curious is that for the 6M or 7M crank?

 

[87witmoreboost]

It shouldn't be pricey if he's a decent guy, maybe charge you one hour shop rate. If he feels for you a nice guy would do it for free. As long as he has V blocks, and a dial indicator.

Sounds about right. I have v-blocks and a dial I can grab from work. I will do it tomorrow and post results. This is a good idea because it's really unlikely that a rod bearing surface would be bent if it dials out within spec on a main bearing surface. I don't even know how a shop would measure a rod bearing surface. And I of course don't mean surface finish - just if they are straight.

I'll dial it tomorrow and see how it goes.

 

[dumbo]

Sounds about right. I have v-blocks and a dial I can grab from work. I will do it tomorrow and post results. This is a good idea because it's really unlikely that a rod bearing surface would be bent if it dials out within spec on a main bearing surface. I don't even know how a shop would measure a rod bearing surface. And I of course don't mean surface finish - just if they are straight.

I'll dial it tomorrow and see how it goes.

Read this, its run out your concered about with the fall. You need a PERFECTLY(I think) level surface, V blocks, and a mag base dial indicator.

.0024" isn't a lot...

http://cygnusx1.net/supra/Library/TSRM/MK3/manual.aspx?S=EM&P=83

 

[mk3ukr]

I received recently crank by mail and woman in the post office dropped it from the shelf in front of me :icon_mad:
I took it to the crankshaft guy, he measured 0.12mm radial runout. TSRM specs 0.06mm max. The guy took the hammer and gave few blows to the crank. It took him less then 5 minutes to bring it to 0.025mm out of straightness :icon_bigg

 

[IJ.]

I'd just check it for straightness most are out a bit anyway and need a hit with an air chisel to get back in line

 

[staticpage]

I would think it would be ok. These iron blocks support the crank a lot when there caped in, not like the Honda's I use to work on, where it's the crank that supports the block. In the Honda world your crank must be perfect for a great build.

 

[IJ.]

I would think it would be ok. These iron blocks support the crank a lot when there caped in, not like the Honda's I use to work on, where it's the crank that supports the block. In the Honda world your crank must be perfect for a great build.

WTF are you on about?

In ANY engine other than one with roller bearings the Crank rides on a film of Oil and should never touch the bearings so how would a crank support the block? :nono:

 

[dumbo]

WTF are you on about?

In ANY engine other than one with roller bearings the Crank rides on a film of Oil and should never touch the bearings so how would a crank support the block? :nono:

Thank you IJ. :nono:

Straighten with a hammer eh, they don't teach you that in school lol. I wish the groups crank was outta round, woulda learned something new.

 

[adampecush]

Read this, its run out your concered about with the fall. You need a PERFECTLY(I think) level surface

e.g. a granite table.

 

[Mk3runner]

reminds me of taking a chevy cam to a granite table and seeing how warped it was.

lol at honda boy.

 

[IJ.]

Thank you IJ. :nono:

Straighten with a hammer eh, they don't teach you that in school lol. I wish the groups crank was outta round, woulda learned something new.

Pro's use a blunt air chisel
(I was horrified when my crank shop gave me a tour as I expected there to be some high tech press involved)

 

[87witmoreboost]

Pro's use a blunt air chisel
(I was horrified when my crank shop gave me a tour as I expected there to be some high tech press involved)

Ha! I'll leave that to the pros. Hammer works for me

 

[staticpage]

WTF are you on about?

In ANY engine other than one with roller bearings the Crank rides on a film of Oil and should never touch the bearings so how would a crank support the block? :nono:

thats a pretty aggressive post in my opinion.

look man i don't clam to know more than any one here so I don't want this to get ugly, just saying. but i would like to state what i believe happens. In both weak blocks and rigid blocks. You asked “what I was on about”

we both agree that the crank rides on oil. But then why bolt the heck out of the crank caps if it just rides on a thin film? Because that thin film is transferring the cranks load to the bearings then the bearings transfer that load to the block. In a weak block like a sleeved open-deck block (honda) what actually happens is the crank keeps things together while the block flexes. There fore you must have a perfect crank to make the build last. In a rigid block, I would assume like the toyota's iron closed block. The block holds the bearings more firmly in place then on down the line to the oil film then the crank. There for I think its not as critical that the crank be perfect.

I have a article that touches base on this issue by Larry Widmer some place. This is where I got to thinking about it years ago when I built a b18. I used a dart block because dart claims that there blocks are more rigid with more webbing to stop block flexing.

 

[IJ.]

thats a pretty aggressive post in my opinion.
look man i don't clam to know more than any one here so I don't want this to get ugly, just saying. but i would like to state what i believe happens. In both weak blocks and rigid blocks. You asked “what I was on about”

we both agree that the crank rides on oil. But then why bolt the heck out of the crank caps if it just rides on a thin film? Because that thin film is transferring the cranks load to the bearings then the bearings transfer that load to the block. In a weak block like a sleeved open-deck block (honda) what actually happens is the crank keeps things together while the block flexes. There fore you must have a perfect crank to make the build last. In a rigid block, I would assume like the toyota's iron closed block. The block holds the bearings more firmly in place then on down the line to the oil film then the crank. There for I think its not as critical that the crank be perfect.

I have a article that touches base on this issue by Larry Widmer some place. This is where I got to thinking about it years ago when I built a b18. I used a dart block because dart claims that there blocks are more rigid with more webbing to stop block flexing.

So what?

Don't post garbage and I won't call you on it.

ALL cranks need to be "perfect" anything less why bother?

You "assume" too much, the 7M while being iron is a big wet noodle at anything over 8000 rpm/500 rwhp and no amount of stiffness in a crank is going to change that. (if anything it would promote catastrophic failure, guess what the Damper on the end of the crank actually does)

Trust me it won't get "ugly"

 

[suprarich]

I would think it would be ok. These iron blocks support the crank a lot when there caped in, not like the Honda's I use to work on, where it's the crank that supports the block. In the Honda world your crank must be perfect for a great build.

What IJ is doing is protecting the other readers who might read your mis-informed post, then go out and try installing a bent crank into a straight hole, then having the bearings wear funny. When I read your post, it sounds as if you think bolting down the crank into the mains will make the crank straight. Now we don't want people thinking that it will be "ok" do we?

 

[87witmoreboost]

So I grabbed a dial indicator, stand, and v blocks from work. The v-blocks were too wide to fit on the crank.

As I sat and stared at the crank sitting in the block, I wondered how I would be able to measure it without good v-blocks. And then it hit me - why not do it right in the block? If it measures true in it's future home, it's all that matters.

I set up the dial on the edge of the block and measured them all. They were all dead nuts, under 0.001" runout all around. I was expecting a ton of runout after the fall but checked all three times - still dead on.

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