Review on 🚀 Improve Performance with ATP Automotive Graywerks 101140 Exhaust Manifold by Troy Jennings

How do I start. I chose this manifold for my Chevrolet 230 because it came with studs and gaskets. The outlet was about 1/4 inch narrower than stock. I had to crush it to open it. I spent an hour screwing in the screws and found that the dowel holes were preventing me from aligning the other screw holes. I had to grind the holes for the pins 1/8 inch. I also had to machine one of the stock clamps to fit properly. Add at least $10 for a good carbide carving tool when you buy it, and be prepared to spend a lot of unnecessary machining time to get it working. Update: After driving around a bit with the jet installed, I noticed the vibrations in the motor when I stepped on it. I believe this is due to excessive back pressure from the smaller exhaust port and intake ports against the engine head. Will be replaced with the original manifold which had a split leak. Update 2: I've added photos of the intake side comparing the original GM manifold. You can see where at the new sewer the area should be opened more. I've measured the difference in ports up to 3/16 inch.