Dorman-branded Chinese-made exhaust manifolds: buyer beware!
06-26-2008, 01:12 PM
#1
Burning Brakes
Thread Starter
Dorman-branded Chinese-made exhaust manifolds: buyer beware!
I've got some new manifolds. 
I'm in the middle of a body-off chassis resto, at the end of which I want to install a new stainless exhaust and mufflers. I want to fit dual 2.5" pipes so I decided to upgrade my manifolds. Since I'm in the UK, shipping and import tax on manifolds or coated headers delivered from the USA makes them very (very) expensive. But I found some new 2.5" outlet cast manifolds on eBay.de (Germany) for a good price - about USD 360 delivered - from a reputable seller. So I bought them.
These are Chinese copies, and not good ones. I wasn't expecting them to be brand new Chevrolet stock for this price, but I didn't expect them to be this bad.
Things started off OK. The new ones have brackets cast into them that I'll have to grind off. (I expected this.) They match the bolt pattern and are the right size.
But the casting quality is just appalling. One manifold evidently has a porosity problem and holes have been filled with some kind of filler. I'm assuming the holes don't go right through the metal because I don't suppose the filler will last long at manifold temperatures. Surely they should have been welded if so.
And they badly need porting to be as free-flowing even as the low-grade original manifolds I'm removing. There are huge lumps in the casting that reduce the cross-section of the inlet holes. Similar lumps aren't in the GM castings:
I'll speak to the eBay vendor in the morning and find out what's going on with the porous one. I don't think it's acceptable. Am I being unreasonable? Is this sort of repair normally acceptable for low-quality exhaust castings?
I post this story so people considering the same option are better educated than I was. The brand of the castings (evidently they've come from China to me via America and Germany) is Dorman. They're for sale in a number of US outlets for about $90 each. Buyer beware!
I'm in the middle of a body-off chassis resto, at the end of which I want to install a new stainless exhaust and mufflers. I want to fit dual 2.5" pipes so I decided to upgrade my manifolds. Since I'm in the UK, shipping and import tax on manifolds or coated headers delivered from the USA makes them very (very) expensive. But I found some new 2.5" outlet cast manifolds on eBay.de (Germany) for a good price - about USD 360 delivered - from a reputable seller. So I bought them.
These are Chinese copies, and not good ones. I wasn't expecting them to be brand new Chevrolet stock for this price, but I didn't expect them to be this bad.
Things started off OK. The new ones have brackets cast into them that I'll have to grind off. (I expected this.) They match the bolt pattern and are the right size.
But the casting quality is just appalling. One manifold evidently has a porosity problem and holes have been filled with some kind of filler. I'm assuming the holes don't go right through the metal because I don't suppose the filler will last long at manifold temperatures. Surely they should have been welded if so.
And they badly need porting to be as free-flowing even as the low-grade original manifolds I'm removing. There are huge lumps in the casting that reduce the cross-section of the inlet holes. Similar lumps aren't in the GM castings:
I'll speak to the eBay vendor in the morning and find out what's going on with the porous one. I don't think it's acceptable. Am I being unreasonable? Is this sort of repair normally acceptable for low-quality exhaust castings?
I post this story so people considering the same option are better educated than I was. The brand of the castings (evidently they've come from China to me via America and Germany) is Dorman. They're for sale in a number of US outlets for about $90 each. Buyer beware!
06-26-2008, 04:40 PM
#5
Burning Brakes
Thread Starter
When I've finished the body-off I might consider engine upgrades from the stock crate 350 that's in there at the moment. I want a new stainless exhaust to match the refurbed chassis and it makes sense to install an exhaust that can cope with any engine upgrades. Hence a 2.5" exhaust.
The original manifolds have a 2" or 2.25" outlet so installing a 2.5" exhaust system would presumably have been pointless given this bottleneck at the engine end. Thus a desire to find 2.5" manifolds to replace the existing ones.
The original manifolds have a 2" or 2.25" outlet so installing a 2.5" exhaust system would presumably have been pointless given this bottleneck at the engine end. Thus a desire to find 2.5" manifolds to replace the existing ones.
06-26-2008, 04:43 PM
#6
Le Mans Master
send them back...... get your original ones sandblasted and painted.... and ported if you want
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06-26-2008, 07:14 PM
#7
Burning Brakes
I had the same results with the same exact castings sold by Dorman. I only paid $57 each + a shipping fee, so I wasn't too upset that I had to do some porting work to make them flow better.
I did not have the porosity issue with mine though, that bothers me and I would complain about that.
Had mine coated and cured by a local guy and they came out nice.
Lotta work though.
I did not have the porosity issue with mine though, that bothers me and I would complain about that.
Had mine coated and cured by a local guy and they came out nice.
Lotta work though.
