TBI big block exhaust manifold brands?

[someotherguy]

Looks like 4 available choices - 2 that look like your typical white box Chinese offerings with a 1 year warranty (SKP, Davico) and then there's Dorman (also likely Chinese but probably actually produced by Dorman), and ATP, with those choices offering a "limited lifetime" warranty. ATP boasts improved metallurgy in their marketing stuff. They cost a little bit more than Dormans, a little under $100/ea.

Anybody here bought/installed any of these in the past few years? Fitment, quality issues?

Thanks,
Richard

 

[packer0440]

I did try one of the China ones, they fit fine and do work, the only issue I had was that there was excess casting slag in between the runners that interfered with the heat shields for the plug wire boots, which in turn made it hard to put the spark plugs in. A few minutes with a grinder could probably fix this pretty easily.

Also, for some reason the aftermarket ones have slits cut between each port, while the stock ones don’t have this slit. Don’t think it makes a difference, but interesting.

 

[Schurkey]

Wild Guess with No Evidence: All of those manifolds come from the same foundry.

The only aftermarket iron exhaust manifolds I've bought have been Dorman-branded. Every one has been a victim of crappy casting/machining techniques. Every one has been Chinese. I'm told by my favorite automotive machinist that the Dorman "Vietnamese" manifolds are even worse than the Chinese-sourced units.

The Dorman Trailblazer Six-Popper manifolds are all warped when they come out of the box. Theory is that they're machined when still-warm from casting, then the manifold "settles down" as it cools, and warps from residual stresses. I've never had one crack like the Genuine GM manifolds are infamous for, but they've leaked after a couple of years. The gasket surface is rough--high-speed machining--they look like they were machined by kicking them across a concrete floor by ten-year-olds until they were "flat".

Here's a photo of Dorman "Corvette big-block" replacements, complete with gigantic iron booger on driver's side manifold, hanging out into the exhaust flow:

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This is a manifold runner from the passenger's side manifold, 674-505.

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Note that the gasket surfaces have been re-machined by my guy. They were unacceptably rough out-of-the-box. When buying any Dorman manifold--and by extension all the other aftermarket iron manifolds--you'll need to check the casting for defects, and the gasket surfaces for flatness and smoothness, and don't be surprised if they have to be touched-up with a die grinder and rotary file, then planed before you can install 'em.

Humans have been casting iron for more than a thousand years. You'd think they could take some pride in their work instead of churning out junk.

 

[Erik the Awful]

Holy crap, that last picture looks terrible. Did they lose their sand and use gravel as casting media?

 

[someotherguy]

Wild Guess with No Evidence: All of those manifolds come from the same foundry.

The only aftermarket iron exhaust manifolds I've bought have been Dorman-branded. Every one has been a victim of crappy casting/machining techniques. Every one has been Chinese. I'm told by my favorite automotive machinist that the Dorman "Vietnamese" manifolds are even worse than the Chinese-sourced units.

The Dorman Trailblazer Six-Popper manifolds are all warped when they come out of the box. Theory is that they're machined when still-warm from casting, then the manifold "settles down" as it cools, and warps from residual stresses. I've never had one crack like the Genuine GM manifolds are infamous for, but they've leaked after a couple of years. The gasket surface is rough--high-speed machining--they look like they were machined by kicking them across a concrete floor by ten-year-olds until they were "flat".

Here's a photo of Dorman "Corvette big-block" replacements, complete with gigantic iron booger on driver's side manifold, hanging out into the exhaust flow:

You must be registered for see images attach

This is a manifold runner from the passenger's side manifold, 674-505.

You must be registered for see images attach

Note that the gasket surfaces have been re-machined by my guy. They were unacceptably rough out-of-the-box. When buying any Dorman manifold--and by extension all the other aftermarket iron manifolds--you'll need to check the casting for defects, and the gasket surfaces for flatness and smoothness, and don't be surprised if they have to be touched-up with a die grinder and rotary file, then planed before you can install 'em.

Humans have been casting iron for more than a thousand years. You'd think they could take some pride in their work instead of churning out junk.

I have low expectations of the Dormans, but I think they actually do cast their own parts; not sure where it was I saw it but some of their stuff actually has their logo in the casting. I have even lower expectations of the 2 brands with the short warranties and cheaper price than Dorman. I'm leaning towards the ATP's.. just hoping someone here has been down this road like you have and has some info on that particular brand.

Richard

 

[Schurkey]

The Dorman logo is cast into at least some of the manifolds I've bought. Doesn't mean that the foundry doing the casting can't put someone else's logo in the mold next week. I doubt that Dorman "owns" the foundry. I'd expect they have a contract with whoever they can get product from the cheapest. (Which may be why we're seeing Viet Nam-sourced manifolds.)