Exhaust Manifolds, C3, LS4

[Raymond W.]

I'm planning to replace the attaching bolts, 16 in all, for the exhaust manifolds. I have the Chassis Service Manual, but can't seem to locate a sequence for removal and re-tightening. Is there a bolt pattern that should be followed? Am I correct in identifying the torque specs at 20 lb. ft.? I was planning to remove one at a time and replace with new, but would want to follow a pattern if available? These manifolds were previously installed using gaskets for which I do not intend to remove or replace. I'm hoping for some suggestions...thanks.

[Patrick H.]

Re: Exhaust Manifolds, C3, LS4

Ray,

I'd highly recommend getting rid of the exhaust gaskets, having the manifolds surfaced, and then reinstalling. I thought I "knew better" than GM and put exhaust gaskets on my SB when I rebuilt it. After burning through a set every year and countless leaks I took off the manifolds, resurfaced them, and used no gasket. Zero issues since then. Even if they're not leaking now I'd suggest they will in the future.

I usually tighten from the center outward in 10 lb-ft increments.

FYI, I've got your pics, but have to get them ready to e-mail.

Patrick

[Joe L.]

Re: Exhaust Manifolds, C3, LS4

Patrick------

I agree; the exhaust manifold gaskets are not necessary and, certainly, were never originally used. I'll bet Ray's manifolds will check out ok to use as-is.

As far as your gasket experience goes, they burned out because you used the wrong kind of gaskets. I'm assuming here, though, that you used the "sandwich" style gaskets that are supplied with many engine gasket sets, including many GM gasket sets. If so, those ain't the ones you want to use. If one is going to use gaskets, the ones to use are MLS (multi layer steel). I don't know how to obtain these for a small block, but I do know how to obtain them for a big block.

[Patrick H.]

Re: Exhaust Manifolds, C3, LS4

Joe,

Yes, I even tried a few different brands, types, and qualities. None of them worked.

No gaskets works exceptionally well.

Patrick

[Raymond W.]

Re: Exhaust Manifolds, C3, LS4

Patrick and Joe...I understand all your saying about the gaskets, just not sure I'm up to taking that next step in the process. The car was rebuilt back in 1997, which predates my ownership by 6 years. I'm looking at the receipt dated that same year from Summit Racing in Tallmadge, Ohio where a Gasket Kit is listed. Whatever's on there now, they've been leak free for 10 years, as is the entire current exhaust system that I added to from the front pipes back. I'll probablly leave well enough alone for now...maybe winter job. With no removal pattern to speak of, I'll follow the suggestion of working from center bolts outward. Thanks, Ray