Now that the new header has been in place for some months, has the combustion changed? I once bought a '73 MGB that had a steel header that replaced the stock cast iron manifold. I noticed the 2 outboard cylinders (1 & 4) ran rich, while the 2 inboard cylinders (2 & 3) ran lean. I noticed something unusual about the MGB head: The 2 inboard cylinders share an exhaust port whereas the outboard ones do not. Also, the stock manifold joins the 2 outboard cylinders in the manifold before sending them down a long headpipe. The head pipe eventually joins the 2 pipes much farther down the line. As for the steel header, it just balanced the backpressure differently even though it had no obstructions. I changed it back to a stock manifold and the problem went away.
I have not driven it much since the install. Although initial few runs were very good. Lots of power and acceleration. Good points though. I will follow up later when the weather warms up and give it some hard runs to see if there are any issues
@@AlexPlatacis It seems to me that the designers of the MGB exhaust system had their work cut out for them when half the cylinders have to share an exhaust port and the others don't. I've never seen another engine that did that. Most header designers seek to make high flow-rate pipes of equal length on each port. That doesn't really apply to this engine's head. This may be why I keep reading how the stock manifold arrangement is about as good as it gets for that engine. YMMV. You do good work. I hope these fixes you're making get your overheating problems resolved.
@wilycoyote5360 yeah, frankly, i think the carb heat issues were due to the manifold porting, and selection of the DCOE45. The increased airflow increased the manifold temp. (And reduced fuel mileage). The addition of the header seems to have re-balanced the system. In my case at least. I do feel a bit of a performance improvement. If only by the seat of my pants. Not sure it is measurable.
Now that the new header has been in place for some months, has the combustion changed? I once bought a '73 MGB that had a steel header that replaced the stock cast iron manifold. I noticed the 2 outboard cylinders (1 & 4) ran rich, while the 2 inboard cylinders (2 & 3) ran lean.
I noticed something unusual about the MGB head: The 2 inboard cylinders share an exhaust port whereas the outboard ones do not. Also, the stock manifold joins the 2 outboard cylinders in the manifold before sending them down a long headpipe. The head pipe eventually joins the 2 pipes much farther down the line. As for the steel header, it just balanced the backpressure differently even though it had no obstructions.
I changed it back to a stock manifold and the problem went away.
I have not driven it much since the install. Although initial few runs were very good. Lots of power and acceleration.
Good points though. I will follow up later when the weather warms up and give it some hard runs to see if there are any issues
@@AlexPlatacis It seems to me that the designers of the MGB exhaust system had their work cut out for them when half the cylinders have to share an exhaust port and the others don't. I've never seen another engine that did that. Most header designers seek to make high flow-rate pipes of equal length on each port. That doesn't really apply to this engine's head. This may be why I keep reading how the stock manifold arrangement is about as good as it gets for that engine. YMMV.
You do good work. I hope these fixes you're making get your overheating problems resolved.
@wilycoyote5360 yeah, frankly, i think the carb heat issues were due to the manifold porting, and selection of the DCOE45. The increased airflow increased the manifold temp. (And reduced fuel mileage). The addition of the header seems to have re-balanced the system. In my case at least. I do feel a bit of a performance improvement. If only by the seat of my pants. Not sure it is measurable.