I have a 87 Monte Carlo LS with what I believe to be an HO 305. The reason why I'm not sure is because it's made of so many different car's parts. Not sure if the engine is stock but the head's casting was 081 so I assume it's an HO. From research I found that it's an LG4 which was machined for a roller cam but was flat tappet. I had an old cam laying around so I threw it in. It's a comp cams 08-300-8 (Camshaft, Hydraulic Roller Tappet, Advertised Duration 262/264, Lift .450/.480, Chevy). I did that as well as put an Edelbrock torker II intake on it. It has a stock q-jet on it as well. Just to mention I used a head gasket from a 350 so I know that lowers compression but I didn't care at the time. I couldn't get all the exhaust manifold bolts in and knew it was going to leak. I started it anyway and took it for a spin. It felt slower than before and I'm wondering if this could be a result of the manifold leak. It's so bad you can see flames coming out of the head. I plan on fixing it tomorrow but I'm just wondering what you guys think. Im not 100% that the timing is dialed in either so it might be that. Just give me your thoughts.