Exhaust leak at gasket (I think)

[Jeff Berk]

I did a lot of miscellaneous work on my 260z to get it ready for the Summer. I was ecstatic that it started after rebuilding the dome-top carburetors. While I was working on the carburetors, I removed the intake manifold to polish it up and coat it with a clear heat resistant paint.

A minute or so after the car started, smoke from around the manifold gasket began to appear. 

I'm assuming I need to pull the intake and exhaust manifolds off and reinstall it but I'm not sure what I did wrong the first time. One thing I think I did wrong was to not  use a torque wrench because it was difficult to reach the bolts.  Are there any other pointers you could provide? 

[Reptoid Overlords]

I'd say there's a pretty good chance that the existing gasket might have torn, or at the very least become unseated from removing the intake manifold.

I've never used a torque wrench on the bolts. Only heat cycled and re- tightened. I plan to use the stud kit when I put the engine I'm rebuilding back together.

It might be time to replace it.

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[Dave WM]

did you use any kinds of lubricants when loosening the exhaust manifold nuts? if so likely they are just burning off, see if it continues to smoke after several minutes. If you have a leak I would think you could hear it. use a rubber heater hose, listen to one end and move the other around near the exhaust manifold. if its leaking you will hear it. And yes you should try to use a torque wrench, and then go back after a couple heat cycles and check again. did you reuse the manifold gasket?

[Dave WM]

oh and there you go differing opinion on using torque wrenches. Granted not very accurate when swivel and ext are installed, but I still used one IIRC.

[Jeff Berk]

Thanks for the opinions.  I replaced the gasket with I think a Felpro brand gasket.

I think I used an antiseize everywhere so maybe that's where the smoke came from.

[Captain Obvious]

Yeah, it's going to take a little while for that to burn off. Unless you can hear a leak, it's probably fine. Stinky, but fine.

After everything has heated up once or twice, maybe re-torque everything to make sure it's still tight.

[Zed Head]

Don't overtorque.  It's hard to find a good reference, and there are different types of "anti-seize" out there but this references implies that 2/3 of normal is a good rule of thumb.

http://www.alliedsystems.com/pdf/Wagner/Forms/80/80-1057.pdf

I spent extra time torquing mine to just right but when I detected a small leak I went right back to crank it down until stops mode. 

[Jeff Berk]

FYI... Thanks all

After running it outside for a half hour, it stopped smoking so all the oils and anti seize must of burnt off. 

I was sure I screwed up something.

[Captain Obvious]

18 hours ago, Jeff Berk said:

I was sure I screwed up something.

Don't sell yourself short. You may still have.  

Seriously though, glad the smoke wasn't anything serious.