Header question

[skippyf15]

I was talking to an old timer about puttting headers on my truck. He said it would be a mistake because the engine wouldn't warm up because the headers would pull the heat away from the engine. I thought that was the point of headers. He says thats why the factory uses cast iron manifolds, to hold the heat and to slow the flow. Am I missing something or has he had a stroke or something. My momma told me that I should always respect eldery people.

[DanSanDiego2000]

I'd be willing to bet that part of the reason exhaust was largely made in cast iron was that it was cheap, durable and could be mass-produced with consistency. Imagine trying to bend smooth, consistent headers for the millions of vehicles produced. Long before CNC computer numerically controlled benders, or even the massive powered hydraulics of today, earlier generations could never have cranked-out the billion plus vehicles over the last 100 years, and could have never hand built all those headers with any degree of consistency or accuracy.
The headers are going to improve your power through reduced restriction. Reduced restriction also means better exhaust velocity. So, the same amount of exhaust is able to maintain it's speed exiting through headers (due to decreased restriction). If the exhaust gasses are able to retain their heat on the way out, they also maintain a higher velocity. So, header wraps keep exhaust gasses hotter, and keep exhaust velocities higher, netting more power. The cast iron was able to keep more heat in the exhaust gas, but are restrictive. A cast iron header has been used in some vehicles successfully, but if you combine the low-restriction headers, with the header wrap, you will outperform most any other stock or aftermarket combo. I have also heard it said that Ceramic Coated headers help to keep in the heat, lower under-hood temperatures, and provide at least a little of the advantages afforded by the header wrap. The wrap can look cheesy (cheese-cloth pun intended), but Jegs offers black wraps, white, copper and even reflective shields (like aluminum foil blankets).
So, as you mentioned, respect the elders, but respect Mother Nature, and the laws of nature and physics. I think he may have tried to give you an over-simplified version of what I just said.

Recently, I added Ceramic Coated Clifford Headers on my inline 6, 240cid engine. They were too pretty to wrap, and the ceramic coating seemed to keep the engine bay cool enough. The Clifford Water Heated Intake, and Demon 2bbl Carb all woke up my sleepy 6 tremendously. I had a carb problem, and I am just awaiting to get my carb back from Demon, put it back together, and see if I can get the 45% increase in torque, and the jump in fuel economy they bragged about. I used to max out at 3000 RPM (it sounded like it was going to grenade if I pushed it further), but with the increase in CFM in, and the decrease in restriction through exhaust, with no other mods, the engine now readily, willingly revs to 4000. Obviously, I am making a lot more power than I ever was before, just from the 1000 rpm increase.

Pheeeew!! That was more than 2 cents worth, but I am excited about this transformation, and I believe you'll enjoy a similar swap, too.

Regards.

Dan

[douglloyd]

Great post Dan! No apologies for length necessary.

Now for the counterpoint/product warnings<g>.

As much as headers boost engine performance, there are things to watch for if you go that route. Our trucks have pretty wide engine compartments - you can practically climb inside and stand up alongside a six - but you will give up much of that room with headers. Many trucks get crossmembers butchered to clear the pipe clusters, a bad thing for a truck you intend to 'drive like you stole'. Also, basic parts removal & installation like starters, trannies and clutch setups takes on a whole new angle. Be sure your driver's side setup clears the steering gear - this is no fun to relocate<g>

Doug

[skippyf15]

Header wrap, improve that much?

[ethan_lanning]

I have a 360 in my 1965 f-100 and it has headers.It seems to run and drive with them alright.but if you do get headers you will be limited on room.because on mine if you need to change the starter then you have to jack up one side of the motor and take off the header.so there are pros and cons when you have headers.

[The Big M]

The headers are going to improve your power through reduced restriction. Reduced restriction also means better exhaust velocity. So, the same amount of exhaust is able to maintain it's speed exiting through headers (due to decreased restriction). If the exhaust gasses are able to retain their heat on the way out, they also maintain a higher velocity. So, header wraps keep exhaust gasses hotter, and keep exhaust velocities higher, netting more power. The cast iron was able to keep more heat in the exhaust gas, but are restrictive.

It should be noted that in this case "reduced restriction" means smooth bends, rather than an increase in the cross-sectional area. If the same volumetric flowrate exists in two different-sized tubes, the flow in the smaller-diameter tube will have higher velocity. This is an important factor in header design.

The advantage of headers is the principle of scavenging. The flow in the collector helps to draw exhaust gases out of the ports.

There may be clearance issues and other design considerations associated with headers, but I'm sure the engine will still warm up.

[DanSanDiego2000]

Going back to the original comment made by the "old timer". He said the engine wouldn't warm up because the headers pulled heat away from the engine. I am not so sure that he was worried about the engine not warming up.... if he was on the same track as I am suggesting, he may be worried about the heat loss from the exhaust, through the headers, into the atmosphere, and the reduction of exhaust velocity. He may have said what he said because it was simple, but may have been suggesting something far more complex. "Scavenging", as The Big M mentioned, is key to the free breathing of an engine. You can't fit 3 or 4 cars into a single lane, and expect them all to merge onto the freeway smoothly. They bump, they grind, they bottleneck, and they slow down.... what a traffic mess (this is a cast iron manifold). Set up 8 lanes, one car per lane, and have them enter the freeway equally spaced apart, and they enter smoothly, no bumps, no deceleration, and no tie-ups, and they can accelerate down the road (this is the header). In fact, the millions of cars that went ahead of them would have caused such a tremendous pull of air, that the following car (or the following exhaust pulse) would be able to "draft" behind the momentum of the car ahead. The exhaust pulse from one cylinder, running through equal length header tubes, will always reach the collector evenly spaced behind the previous exhaust pulse, and equally spaced ahead of the next exhaust pulse. Scavenging, and tuned, equal length headers are all about traffic management.
Yes, they cause extra (or excessive) under-hood temperatures (all the more reason to wrap 'em), they cause starter overheating, steering box interference, etc, etc, etc,.... but if you buy a set specifically designed for your application, or pay the extra coin for custom, buy them coated (Or have them coated), buy them in stainless, but buy equal length, or "tuned", headers, you will feel a seat of the pants improvement, and maybe less pain at the pumps (provided you don't begin to drive like a bat out o' hell with your new-found power).

This is exhausting, too.



Dan