A car buff friend (a GM guy) was looking under the hood of my M GT and said, "they put headers on this thing!"

They obviously are cast iron exhaust manifolds but they are shaped in form and design like headers. So are they a hybred exhaust manifold / header?

 

No they are not but flow extremely well for stock manifolds. Shorty headers will only increase about 3-5 RWHP. For large improvements you need long tube headers.

 

exactly what tmcole said.For cast manifolds you can tell just by looking at them that they flow pretty well due to their "header like" design and I kinda figured all along that shorty headers were not gonna make much of a difference performance wise over the stockers

 

Yeah I was planning on keeping the stock manifolds even with the offroad pipe and cat backs. I might eventually pick up a set of shorties if I find them used or really cheap down the road.

 

Ok, I'm going to ask it.... what exactly are the benefits of headers and how do they differ from an exhaust manifold?

 

The purpose of a header is to facilitate faster flow out of the engine. A header will have a smooth curvature and will come straight out of the block before turning toward the rear of the car.

Many exhaust manifolds are very tight and have sharp turns right off of the block. This restricts the through flow.

The Mustang GT exhaust (stock) has a smooth profile and doesn't make any sharp curves. These are shaped like most headers. If you look at the exhaust manifolds on the GT you will see a straight out with a gentle turn before connecting to the exhaust pipes. This is why my friend said they put headers on that thing!

 

Also, I think most headers have tubes that are all equal in length from the head to the collector, which reduces backpressure and improves breathing.

At least that's what I remember from my old hot-rod days.....

 

Long tubes and equal-length shorties have all equal length tubes for each cylinder. Shorties don't, so the cylinders at the end have little short tubes whereas the first cylinders have the longest, and so on, and so forth...

 

I also thought that headers actually were designed to get hotter faster and stay hot longer to keep the exhaust gasses from expanding due to a drastic temperature change compared to the head port. some racers actually wrap their headers with thermal tape in order to keep them as hot as possible.

 

Yes, this is also why most headers are available with a ceramic coating.