Engine 151 Iron Duke 151 CI O-Ring location

[CJ51980]

I'm in the process of building a 1980 GM 151 CI Iron Duke and the Felpro Gasket kit has a rubber o-ring that has a square cut cross section. I can't find where it it should be installed. It fits perfectly in the Crank hub/Balancer that's behind the crank pulley, underneath the crank bolt. I don't think that's where it goes but not sure.

Thanks for the advice

 

[CJ]

Do you have the gasket set number and can you attach a pic. of the o-ring?
Have you looked at the FSM? -->> GM 151 Factory Service Manual

 

[CJ51980]

Do you have the gasket set number and can you attach a pic. of the o-ring?
Have you looked at the FSM? -->> GM 151 Factory Service Manual

I have a Hayne's 1949-1986 repair manual. It's the O-Ring inside shown in the Pulley Hub, small one next to the Timing cover seal and slid on the rear of the Crank

Photos:

 

[Patrick]

You don’t think it’s for your thermostat housing…

The gasket kit might include a description of its contents.

 

[CJ51980]

You don’t think it’s for your thermostat housing…

The gasket kit might include a description of its contents.

Could be, I was gonna check that but haven't gotten to installing the t-housing yet. Sounds like a good idea, thanks.
It did include a description but It wasn't very thorough.
Thanks again, I'll let you know if that was it..