Broken Crank in my 3FE

[Driving Daisy]

Just had my engine rebuilt and the machine shop repaired #1 and #2 of the crank. Well 1,500 miles later the crank snapped at #1. I should have known there would be a problem with a rear main leak (read lake) from day one.

My question is that the machine shop is telling me there is no reason to pull the head and check the pistons and valves.

My thought is five slugs were slinging around a few times before the engine stopped. Couldn't a piston smack a valve??

This is warranty work for the machine shop, but I have to pull the motor and re-install. I am getting fast at pulling the motor but not looking for a new vocation.

Thoughts and experiences??

Much Thanks

 

[tonkota]

Depends on how bad it broke. If it was flying around in there, then the block is probably bad too. If you need a good block/crank, I have one. I know it's not your deal but let them know. $75 plus shipping. It was turned 10 under when I rebuilt the engine, and then the rear main seal blew out and all the oil went too and the #1 and #6 rod bearigs got pretty hot

Now the block is sitting in the garage.

 

[Mark W]

Depends on how the crank actually snapped. It is as likely for the crank to stay pretty much lined up as a unit as it is for things to spin freely.

It has been a while since I tried, but IIRC you can not remove the crank without pulling the pistons out the top anyway.

Why is this the machine shop's problem.When you say that they repaired #1 and #2... What exactly did they do?

Mark...

 

[Driving Daisy]

Why is this the machine shop's problem.When you say that they repaired #1 and #2... What exactly did they do?

#1 and #2 were shot when I had the engine rebuilt. The machine shop sent the crank out to have both #1 and #2 welded and then machined to match the rest.

The crank snapped on the front side of the #1 connecting rod. The engine spins but the pulley on the front of the crank will not budge by hand.

My worry was the one once the crank snapped the valves stopped but the pistons were still in motion. If a valve was open and the piston came up could it make contact???

 

[Driving Daisy]

Depends on how bad it broke. If it was flying around in there, then the block is probably bad too. If you need a good block/crank, I have one. I know it's not your deal but let them know. $75 plus shipping. It was turned 10 under when I rebuilt the engine, and then the rear main seal blew out and all the oil went too and the #1 and #6 rod bearigs got pretty hot

Now the block is sitting in the garage.

Tonkota,
I will pass the offer along to the machine shop.
Thanks!

 

[Mace]

You can pull the crank with the pistons in it. It is a serious pain in the ass but it can be done.

I wonder if they heated the crap out of it when it was rewelded...

They will know if the valves have hit the pistons when they rebuild the motor..

 

[roscoFJ73]

#1 and #2 were shot when I had the engine rebuilt. The machine shop sent the crank out to have both #1 and #2 welded and then machined to match the rest.

The crank snapped on the front side of the #1 connecting rod. The engine spins but the pulley on the front of the crank will not budge by hand.

My worry was the one once the crank snapped the valves stopped but the pistons were still in motion. If a valve was open and the piston came up could it make contact???

I dont think the valve and piston would meet(crunch) The 3F is not an interference motor ,providing one end of the broken crank is still held down by a main bearing.

Only the newer motors have pistons that travel higher than the lowest point of a valve being open which is why it is crucial to change the timing belt at the required intervals.

I havnt seen too many 3F cranks snap

 

[Mark W]

I had a 2F crank snap at the #3 main journal. Don't remember now if it was right ahead or right behind it. The crank had never been touched. But the engine came out of a parts rig that had suffeedr a roll over before it became a parts rig. Looked like the rig caught air during the roll and came down hard on the rear tires. I assume that the engine was turning and when it came down and grabbed LOTS of traction it stopped it cold. Just like a prop strik in an aircraft. Apparently cracked the crank and it let go a couple of thousand miles later while cruising the highway at 55-60 mph.


Mark...

 

[Driving Daisy]

I dont think the valve and piston would meet(crunch) The 3F is not an interference motor ,providing one end of the broken crank is still held down by a main bearing.

Only the newer motors have pistons that travel higher than the lowest point of a valve being open which is why it is crucial to change the timing belt at the required intervals.

I havnt seen too many 3F cranks snap

Rosco,
That does make me feel better.

Seeing that the rear main leaked from day one whoever worked on the crank was where the problems started.

 

[roscoFJ73]

Rosco,
That does make me feel better.

Seeing that the rear main leaked from day one whoever worked on the crank was where the problems started.

If you have to pull the motor check the rear main seal ,you maybe able to see if its damaged then you know you have Neanderthals working in the shop.
They are relatively easy to put in,having only done 2 myself with no problems.

Otherwise it may have something to do with the crank jumping around because of a clearance problem in the bearing/machining.

 

[pvidrummer]

Just had my engine rebuilt and the machine shop repaired #1 and #2 of the crank. Well 1,500 miles later the crank snapped at #1. I should have known there would be a problem with a rear main leak (read lake) from day one.

My question is that the machine shop is telling me there is no reason to pull the head and check the pistons and valves.

My thought is five slugs were slinging around a few times before the engine stopped. Couldn't a piston smack a valve??

This is warranty work for the machine shop, but I have to pull the motor and re-install. I am getting fast at pulling the motor but not looking for a new vocation.

Thoughts and experiences??

Much Thanks

If that would happen to me I would put in a new or rebuilt short block.
Have you thought of using a 2f engine block instead of the 3f? Is it possible?

 

[Driving Daisy]

If that would happen to me I would put in a new or rebuilt short block.
Have you thought of using a 2f engine block instead of the 3f? Is it possible?

In all honesty I have thought about dropping the whole 6cyl thing and put in a small block chevy!

I can hear the purist now.....

 

[tonkota]

Have you thought of using a 2f engine block instead of the 3f? Is it possible?

It is possible.

http://www.steelnthings.com/TLCA/2Fswap/

I had to buy another crank for my first rebuild - $500
For the 2F swap I bought a 2F short block that needed rebuild - $450

And the internals were less expensive too.