Review on Dorman 674 777 Exhaust Manifold Kit by Chad Baio

Well it fits. That's the only positive thing I can say about this product. I worked as a mechanical engineer in the automotive industry for almost 30 years and should have known better than to buy this aftermarket Chinese junk but I was just trying to get the truck back on the road to sell it. Unfortunately my decision started to haunt me because my daughter drives now (she has an accident with her car). Who knows if cast iron might be close to the right grade. The processing is very coarse compared to the original. Good luck with a good head gasket unless you have a better part than me. Laminated metal gaskets used in this engine require a much smoother sealing surface than this manifold. If you can get your fingernail on the ribs, that's too rough. I had to tweak it just to give it a chance to seal. If you buy this manifold, do yourself a favor and take a good flat file or hand sander to the surface of the seal to smooth it out. Also, ditch the 3 muffler nuts they give you and either buy better ones or reuse the original GM rust nuts. They are better than new ones because the threads are so loose they hardly tighten. Later they get free and you find yourself under the truck again cursing and throwing things (ask me how I know). Also add some washers under the bolt heads holding the manifold to the engine. This manifold is poorly designed because it is very long and the difference in expansion between the manifold and the aluminum cylinder head puts a lot of stress on it during heating and cooling cycles. That makes it bang. Flat washers allow for slight slip rather than excessive loading. My recommendation: Don't be tempted to drop the price on this part and buy the GM part. It can be bought online for about 40% more and you don't have to spend hours preparing to fix the part before you can install it. Sometimes you really do get what you pay for.