New motor not passing leakdown test

[smithrookie]

just put together my new motor (61x head on 62T cases). I sealed it all up and let it sit for 24 hours before doing a leakdown pressure test. I've found that my brand new front crank seal (oem) is leaking pressure. It will drop about 1-2psi a minute when i pressurize to 8psi or so. Is this worth taking the whole motor apart again? Is there anything that could be interfering with the seal?

Thanks
Mike

 

[yamabro]

New crank? Rebuilt crank? Used crank? Need just a little more info.
The flywheel snout of the crank could be worn...

 

[smithrookie]

It was a rebuilt sbt crank purchased from jetmaniac last year. I ran it about 20-25 hours in my 61x motor last year. I failed to grease the crank seal last year when rebuilding due to being a rookie and not reading the manual correctly so it definitely could be worn...

Any options if it's worn? Replace the crank? Run it and pray it doesn't become a problem (seal the crap out of the flywheel cover)

Thanks
Mike

 

[yamabro]

Then your crank could be worn. Really hard to say without a tear down.
If you want "Peace" of mind,... Then tear it down. It's better than a 5 hour run time and a rod hanging out the side of the block.

 

[Big Kahuna]

If you try and run it, it could start sucking air and cause a lean condition.

 

[DAG]

In my opinion its risk vs reward. You have to evaluate that for yourself. Nearly all motors fail leakdown test. Even motors that pass the test and then ran a season and retested will more than likely have a leak. Every 701/760 motor I’ve pulled from a couch has leaked and I’m sure it has leaked for years…


If you have time to fix it, then defiantly fix it. If you did not grease the seals that is definitely suspect and it’s a cheap fix especially if you already have the motor out.

 

[bach6177]

It was a rebuilt sbt crank purchased from jetmaniac last year. I ran it about 20-25 hours in my 61x motor last year. I failed to grease the crank seal last year when rebuilding due to being a rookie and not reading the manual correctly so it definitely could be worn...

Any options if it's worn? Replace the crank? Run it and pray it doesn't become a problem (seal the crap out of the flywheel cover)

Thanks
Mike

Crank seal is probably baked . Just reseal the lower end, new crank seals.


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