A long time back I remember hearing something about running open headers for long periods of time can damage the engine... any truth to this? Difference between shorty style and full length?

 

I've not heard that with headers necessarily but I remember back when I was a teenager in the 60s that I was warned not to drop pipes from the factory exhaust manifolds and run the engine hard for fear of warping an exhaust valve when shutting it down - due to air backing up the exhaust. I guess I could see a possibility of that on running an engine without manifolds or headers at all, but I don't actually remember anyone saying such a thing ever happened to them. But with headers - I think not for sure.

 

Also...you have to watch were you dump them....fiberglass dont car for the heat.....

jack

 

Same thing I've always heard.....urban legend ? or fact ?
I don't know...

 

I heard the same thing many years ago but I figured that if drag racers could run hard and shut their engine off without a problem, it must be more of an urban myth than fact. I never heard of it actually happening to anyone either.

Jim

 

Typically, an engine will run leaner through open headers. If the engine is already on the lean side, then yes, it could be harmful. I would expect shorty's to have a lesser effect but not by much. If the purpose of running open is to maximize power, the carb should be jetted appropriately.

 

I bought a set from Sanderson that are similar to block huggers.. not sure if the sidepipes will line up with them exactly and may have to either tow it or run them open...

 

Have never had any damage except to eardrums.

 

%%%%%%%%%%%%%%%%%%%%%%%%%%

Trying to learn but just how does this work. The engine gets the air/fuel mixture through the carb on a normally aspirated engine not the exhaust. Why would it lean out simply by opening up the exhaust??

Steve

 

I used to take my car to the strip and run it. It was a Chevy II with a 327/375. As I remember it, headers (undercar) weren't available for it at that time so I just unhooked the pipes from the manifolds and ran it that way.

I'd been told the same thing about warping the valves. I didn't have any problem. Race cars are run everyday with open headers without damage so I don't know why you'd have a problem driving a short distance that way, especially since you won't be wide open throttle.

 

There is always some unburnt mixture left in the cumbustion chamber after the exhaust valve closes, contributing to the next cylce's charge. If the open header evacuates this fuel better then the incoming charge has less fuel/leaner. At least that's the way I understood it. Drag race cars(open exhaust)are usually jetted fatter( more air...more fuel).

 

If your exhaust system is restrictive, and they all are to a greater or lesser extent, then running the car for long periods of time, especially at higher rpms, with no other changes to the car, could burn exhaust valves. Happened to me once. The carb is jetted for the closed exhaust system. When you uncork that, the engine wil run leaner. If it runs too lean, for too long, at high rpms or at high loads, you could burn some exhaust valves.

 

I've heard this many times over the years and the most common reason that I've heard is that the exhaust valves need a certain amount of back-pressure to function properly. Allegedly, headers do not allow the required back-pressure. But I'm not an engine guy, so, like you, I don't know if this is true or not.

- Pat

 

Maybe someone needs to submit this as a story idea to Mythbusters.

 

It's never been a problem or concern on these engines, and I guarantee you they're a whole lot more expensive than several Vette engines combined!!!!!!!!!
You can't get much shorter than these ex stacks!

 

I heard the same thing back in the 80's. Someone told me the cold air would cause the valve to warp during the cold month's of the year...

 

Shouldn't that P-51 have an Packard-Merlin engine rather than a RR? Also, is the last photo an A-26?

 

Agreed, my hearing has a dip at 8 Khz from open headers

 

I believe the D model is what came with the Merlin... the others were RR. Or might be the opposite of that.

 

The ORIGINAL Mustang airplane WAS NOT a P-51. It was an A-36 (and originally named an Apache), and ORIGINALLY built with Allison engines (as used in P-40s and P-38s). ORIGINALLY ordered, designed and built for the British to suppliment their limited numbers of Hurricanes and Spitfires.
A hotshot US Army pilot, Major Tommy Hitchcock, along with some influential RAF officers, were able to go before Gen 'Hap" Arnold and tell him about the superior performance of the RR Merlin over the Allison. The Merlin was 300lb heavier, developed 600hp more than the Allison and it had a 2 stage supercharger. This 2 stage supercharger was a BIG plus over the Allison because it provided comparable performance at higher altitudes that the Allison only had down low. This information was emphasized to Gen Arnold, who conceded to allow a small quantity of A-36 Mustangs to be converted with RR Merlins. The XP-51B with a Merlin made its first flight in Nov 42, and as the old saying goes, "The rest is history"!!!!! The Mustang was redesignated P-51 and subsequent production was built with Merlins as well as some earlier A-36 were converted with Merlins.
The P-51B and C were the same plane. The B models were built in Calif (on the site where LA International sits today), and the C models were built in Dallas. These were the "Razor back" versions and the later D models had the bubble canopy design.
B-C model


D model


The Merlin was a Rolls Royce design. Because of insufficient quantities of Merlins to keep up with P-51 production, Packard Motor Co. was contracted to build the Merlin. Thus, the "Packard" Merlin vs the Rolls Royce Merlin---same engine. This was VERY, VERY, VERY common during WWII. For example, the B-17 was a Boeing designed airplane. FOUR airplane companies built B-17s. BOTH General Motors and Ford built Grumman designed TBM (TBF at Ford plants) Avengers. The Wright engines used on the B-17 were built by several companies--------------INCLUDING Studebaker, as seen below on Liberty Belle.




The B-24 Liberator had Pratt & Whitney designed engines, and many were built by Ford. One of the old timers in our group was a B24 pilot, and he said the Ford built P&W engines were constantly having problems (that should make Chevy lovers happy ).

After Dec 7, 1941, MANY, MANY US companies converted to building all kinds of military machines and equipment.
One of the most famous pieces of WWII military weapons, the M1 Garand rifle, was built by MANY companies (and not necessarily firearm companies), one of which was Singer Sewing Machine Co.!!!!
Sooooooooooooooooooo, a P-51 could have either a Rolls Royce or a Packard built Merlin.
Here is one of each.
This is the "Race" (Rolls Royce) Merlin for Dr. Hisey's race modified P-51 (Miss America)

And this is the "Crusing" (Packard) Merlin.




Yep, that's the A-26 that I'm a part time crew member on (and ocassional co-pilot).




And this is the A-26 that my volunteer group is doing a total restoration on.




http://www.youtube.com/watch?v=UIrZWimmN_0