welded 277 crank has issues. What to do?

[gggGary]

It's on a vee block and clamped down hard enough to keep it from wandering around on the table, but not hard enough to deform the bearing shells, as you can see it spins freely.
I made the mistake of buying it off a forum or facebook more than 5 years ago. Guy had it and a cam but never installed. Hughes has a date of 2014 on it. He just tossed it loose in a box to ship so have no idea when where it achieved this state of "true".
Supposedly fresh rods n bearings but no way to know for sure. Small ends look new inside.
Have an opportunity to put together a motor, would like to use this, but?

So somewhere around 8 thou out of true. the high point is at the rod.
Again, the pins are all welded.
My current thought is to squeeze the flywheels opposite the big end see it I can get it "true"
other side has "some" wobble also mebby 2-3 thou.
It's January, thought this might be fun to debate.

@hooser
You other guys are looking anyways!

 

[Jan_P]

Dont know the specs but is it 0.008 mm -- That feels small on a non ground object
Is it not pressed together stock.
How much on the outer end .. Hammer blow ?

 

[Mailman]

This guy had a similar story,

https://www.xs650.com/threads/sos-some-crank-truing-help-required-please.59899/

 

[gggGary]

.0008" or about .02mm It's enough to be visible. Was thinking more along the lines of a very heavy duty C clamp to squeeze. shrug.

 

[WideAWAKE]

We always used a big chunk of brass and a mallet to knock them true when rebuilding a crank.

But yours seem like it’s the actual crank body that’s bent, not run out in alignment on the pin since it’s already welded???

Might need a press.

 

[jpdevol]

very heavy duty C clamp to squeeze

...If runnout at or opposite crank pin. Is the rod side play in spec?

 

[jpdevol]

Hammer blow ?

If 90* from crank pin

 

[gggGary]

...If runnout at or opposite crank pin. Is the rod side play in spec?

haven't checked for excess but they have room to turn freely.
Seems I need to squeeze the fly wheels opposite the rod to bring it in.
Yes with the pins welded would be interesting to know where the bend happens...

 

[jpdevol]

Might need a press.

To squeeze....

 

[jpdevol]

Not getting much "debate" out of me today: I'm all thumbs

 

[gggGary]

Might need a press.

There's a 50 ton press out in the shed....

 

[WideAWAKE]

There's a 50 ton press out in the shed....

Sounds like you got it covered!!! That reminds me, I need to find a press haha!

 

[Signal]

Trueing cranks was explained to me this way:
With the bearing on V blocks (it is different when between centres).
If the run out is max when big end pin is parallel to the bench then the crank wheels are not concentric.
If the run out is max when the crank pin is vertical the crank wheels are not parallel.

Mostly its a combo of the two and after looking at you video I think its the same with your crank.

My weapons of choice for crank trueing are a heavy copper faced hammer for hitting the wheels.
An old cold chisel and a ball peen hammer for spreading the wheels.
A large G clamp for squeezing the wheels. If I have a helper a bench vise is good as well just tricky balancing the crank on your own. I was suprised how well the G clamp worked with an extender bar on the tightening handle.


When you have it right check the crank in a case half, I have had 2 welded cranks that pulled so that the centre bearings lifted when it was rotated. I made a tool to bridge the cam drive sprocket to let me press the crank true. I found using centres in the lathe helped a lot.
I was not easy.
I gave up on one recently and asked an expert to true it.
I have posted on this forum a PDF document from the UK about crank rebuilding and trueing it is full of good info.