Regular torquing of exhaust manifold nuts?

[Guest SteveAS]

Gentlemen, the previous owner of my '38 Special wrote the following, which surprised me:

"I would strongly recommend retourqing all the

exhaust

manifold nuts about every 250 miles or so. If I remember correctly, they take 25lbs.( the retourquing procedure is in the shop manual ) If you don't do this they will loosen and then your manifold will move too much and destroy the gasket creating leaks. If you overtighten, the manifold won't be able to move at all and it will crack!"

I've never heard of having to re-torque exhaust manifold nuts regularly. Is he right about that? Thanks for your help.

[Guest Grant Magrath]

Hmmmm. Maybe once or twice after a rebuild? Doesn't hurt to check I guess!

Cheers

Grant

[Joseph P. Indusi]

After several uses, I retorqued the manifold to head nuts and probably had to do it 2 more times. After that it seems to hold. I had to torque to 30 ft-lbs on a 53 Special using the copper clad gasket set to quite everything down.

Joe, BCA 33493

[Guest SteveAS]

Thanks for your thoughts, gents. I was unsure whether I should loosen and re-torque or simply re-torque the nuts. It sounds like the latter is sufficient.

[Mark Shaw]

The original heavy spring washers (convex) should keep everything at the right tension.

[NTX5467]

The original heavy spring washers (convex) should keep everything at the right tension.

Usually, there is some "retention mechanism" for exhaust manifold bolts. The referenced washers are "it" in this case. We've all probably seen the thin steel straps which go between the exhaust bolt holes on Chevy V-8s, with the tabs which are bent over after the exhaust nuts are given their final torque. PLUS, in the Chevy's situation, the flat "heat" washers which go under the manifold nuts . . . to allow the nuts to torque-down enough to keep things tight, but the manifold to also move during hot/cold cycles to prevent cracking.

If the owner mentioned re-torqueing the nuts that often, then something might have changed from the OEM spec nuts/washer situation. I do concur that when you rebuild an engine, it's always a good idea to re-check the torque of manifold nut/bolts after there's been several complete cold/hot/cold cycles.

Just some thoughts,

NTX5467

[Guest SteveAS]

Thanks for the information on the spring washers, gentlemen. I'll check for the presence of the washers. If they're missing, am I right in thinking I could remove the nuts (one at a time) and install the washers without replacing the gasket?