1990 454 exhaust manifold replacement

[ProFarm]

I need to replace my exhaust manifolds on my 1900 454ss. I am looking at the doorman manifolds at summit. They come with gaskets, but are gaskets necessary since they didnt use them from the factory? TIA

 

[ProFarm]

Anyone please?

 

[studigggs]

The service manual for my 1990 doesn't show any gaskets, but with the reputation of Dorman, I'd be willing to bet that the mating surface isnt a factory fit. I'd use the gaskets if it were me.

 

[Supercharged111]

Why not do headers instead?

 

[Duvall]

I second the remark of using some sort of gasket. Im not sure of the quality of the Doorman gaskets. May want to get a set of Fel-Pro or similar quality.

 

[ProFarm]

Yeah thats what I’m afraid of. I dont want to go with headers because i want to stay as close to stock as i can. I wanted to replace them because the studs on the flanges are so rusted there is no way i can get the remainder of the stud out…is there a con with using gaskets? Thanks

 

[Schurkey]

EVERY Dorman exhaust manifold I've purchased--four of 'em, so far--has had piss-poor casting, rough machining, and the gasket flange has been at the maximum allowable warpage--or more.

Photo 1. Trailblazer exhaust manifold gasket surface--terrible rough machining, plus bonus casting flaw.

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Photo 2. Dorman "427 Corvette" exhaust manifold with cast-iron din_gle berry inside port. (Note--forum software won't let me post "din-gle" as one continuous set of letters. Fookin' censors.)

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I'm told that the Dorman manifolds that are cast in China (like the ones I bought) are actually better than the ones cast in Viet Nam. Holy crap, those must be TERRIBLE.

EXPECT to haul your "new" manifold(s) to a machine shop to get the flange acceptably flat. When I had my guy do mine, he puts them in his parts-cleaning oven for a few days, so they heat cycle a few times before getting machined.

ONCE YOU GET THEM FLAT AND SMOOTH, yes, avoid using gaskets.

 

[ProFarm]

EVERY Dorman exhaust manifold I've purchased--four of 'em, so far--has had piss-poor casting, rough machining, and the gasket flange has been at the maximum allowable warpage--or more.

Photo 1. Trailblazer exhaust manifold gasket surface--terrible rough machining, plus bonus casting flaw.

You must be registered for see images attach

Photo 2. Dorman "427 Corvette" exhaust manifold with cast-iron din_gle berry inside port. (Note--forum software won't let me post "din-gle" as one continuous set of letters. Fookin' censors.)

You must be registered for see images attach

I'm told that the Dorman manifolds that are cast in China (like the ones I bought) are actually better than the ones cast in Viet Nam. Holy crap, those must be TERRIBLE.

EXPECT to haul your "new" manifold(s) to a machine shop to get the flange acceptably flat. When I had my guy do mine, he puts them in his parts-cleaning oven for a few days, so they heat cycle a few times before getting machined.

ONCE YOU GET THEM FLAT AND SMOOTH, yes, avoid using gaskets.

Wow thanks

 

[454cid]

Yeah thats what I’m afraid of. I dont want to go with headers because i want to stay as close to stock as i can. I wanted to replace them because the studs on the flanges are so rusted there is no way i can get the remainder of the stud out…is there a con with using gaskets? Thanks

Wait what? The studs are rusted.... so why are you trying to replace the manifolds?

 

[ProFarm]

Wait what? The studs are rusted.... so why are you trying to replace the manifolds?

there is no way (with the tools and know how i have) I can remove the remainder of the flange studs from the flange holes. I assume they are threaded...