Exhaust Manifold Help

[tj43]

So, after swapping the engine on my 88 350TBI Suburban, I have a recurring exhaust leak. After about 3000 miles, the manifold on the driver's side (rearmost cylinder) developed a leak. I replaced the gasket, re-torqued, and everything was fine . . . for about 3000 miles until it happened again.

What am I doing wrong? I am using OEM style hardware with the locking tabs. Is there a better gasket or upgraded hardware that I should be using? Any tips or trick would be appreciated.

Thanks,
TJ

 

[fast 99]

Get the manifold milled or sanded flat, high temp RTV. NO gasket.

 

[Snoots]

As @fast 99 said but I've doubled up on the exhaust gaskets and everything has been happy for many years. No RTV used.

 

[Craig Nedrow]

Pardon Our Interruption

Dont use the cheesy skinny steel ones, use a good thick gasket.

 

[bucket]

It's simple, don't use gaskets. GM didn't use them to begin with. Manifolds seal fine without gaskets.

 

[fast 99]

Gaskets [unless stainless] will tear from expansion of manifold when hot. Manifold will initially seal but won't last over the long term.

 

[Bextreme04]

Remflex gaskets will not leak and will last forever. Stay away from felpro and other cheap, thin exhaust gaskets. Remflex or nothing(like bucket suggested) would be my recommendation.

 

[tj43]

Thanks. I’ll check the flatness (is that a word?) of the manifolds and then try them gasketless with some high temp RTV.

The gaskets I was using were the metallic 3 piece ones.

Side question: any experience with the Hooker SBC manifolds. They look great. If they are high quality, fit these trucks, and will work with my OEM AC/PS bracket, I may buy a set.

 

[Rustisbest]

Pardon Our Interruption

Dont use the cheesy skinny steel ones, use a good thick gasket.

Those are what I've always used with headers

 

[Gander]

Side question: any experience with the Hooker SBX manifolds. They look great. If they are high quality, fit these trucks, and will work with my OEM AC/PS bracket, I may buy a set.

I’ve wondered about this as well

 

[Old Guy Bill]

I've been running the Hookers for about six months now.
Worked fine with Vintage Air A/C brackets.
No problems with them at all, fit & look great.

 

[xm20k]

Check to make sure all the bolt holes will line up and that all three surfaces are flat with each other. I've seen these things warp to point you could only ever get two bolts in them when you tried to remount them the end ports spread away from the center or vs versa. Not as often but I have seen them twisted as well. Somehow, they were on the engine fine but after being off for a while they seem to have shifted.

I've scrapped a lot of SBC exhaust manifolds over the years due to warping.

 

[tj43]

I've been running the Hookers for about six months now.
Worked fine with Vintage Air A/C brackets.
No problems with them at all, fit & look great.

Awesome. Thanks for that info. Any chance you could snap a pic of that Vintage Air bracket? I’m not sure how close it is to the OEM bracket. This is the OEM bracket:

 

[TomR10]

Copper coat. Works great on head gaskets and exhaust. Currently on the header gaskets on my truck. Blew the head gaskets twice on my Harley before using it. Cummins guys use it on the head gaskets before throwing on a big turbo.
Permatex Copper

 

[bucket]

Check to make sure all the bolt holes will line up and that all three surfaces are flat with each other. I've seen these things warp to point you could only ever get two bolts in them when you tried to remount them the end ports spread away from the center or vs versa. Not as often but I have seen them twisted as well. Somehow, they were on the engine fine but after being off for a while they seem to have shifted.

I've scrapped a lot of SBC exhaust manifolds over the years due to warping.

They typically pull together, rather than spread apart. You can buy a specific spreader tool to use while installing, to get the bolt holes lined up.

At any rate, it's likely not the issue in this case, since the manifolds have already been removed and installed a couple times.