Ever start an engine without headers ??

[puppster]

Muffler bearings? Are they expensive? That takes me bake a long way, we had a good friend in high school convinced he needed new muffler bearings. Seriously, I originally posted that I had heard that you could do damage by running no exhaust headers, but I don't really know. However I do know that if you have a refrigerator on your front porch, you can run an engine without headers. Remember I have done this before, but we did have to mow around car when we cut the grass.

[onefastmustang]

$49.99 for muffler bearings.. Good deal here..

http://kalecoauto.com/index.php?main...products_id=10

[Excaliber]

eh eh, thats funny.

[michel schryer]

I guess I will wait 'till I get my stuff,It's no big deal to wait a couple weeks,I'm on my second summer already building so what's a week or two.
Thanks for your comments guys !

[HI Cobra]

Loved the "O" pipe dual pipes for only $99.95.
This Kalecoauto has some great deals.

[Double Venom]

Ernie,
I thought you really stepped on my toes needlessly, BUT, I decided to do a little research and YOU are basically right. What normally happens when the engine is run with no exhaust, it will and can cause all the listed problems BUT.... it is normally the fault of the air/fuel mixture leaning out! This is what can casue all the damage in time.

The old wives tale is -at least partially true- but is not a hazard in itself!

Copied from "exhaust" tech.......
Destroying a myth.

Some say that "an engine needs backpressure to work correctly." Is this true?

No. It would be more correct to say, "a perfectly stock engine that cannot adjust its fuel delivery needs backpressure to work correctly." This idea is a myth. As with all myths, however, there is a hint of fact with this one. Particularly, some people equate backpressure with torque, and others fear that too little backpressure will lead to valve burning.

The first reason why people say "backpressure is good" is because they believe that increased backpressure by itself will increase torque, particularly with a stock exhaust manifold. Granted, some stock manifolds act somewhat like performance headers at low RPM, but these manifolds will exhibit poor performance at higher RPM. This, however does not automatically lead to the conclusion that backpressure produces more torque. The increase in torque is not due to backpressure, but to the effects of changes in fuel/air mixture, which will be described in more detail below.

The other reason why people say "backpressure is good" is because they hear that cars (or motorcycles) that have had performance exhaust work done to them would then go on to burn exhaust valves. Now, it is true that such valve burning has occurred as a result of the exhaust mods, but it isn't due merely to a lack of backpressure.

The internal combustion engine is a complex, dynamic collection of different systems working together to convert the stored power in gasoline into mechanical energy to push a car down the road. Anytime one of these systems are modified, that mod will also indirectly affect the other systems, as well.

Now, valve burning occurs as a result of a very lean-burning engine. In order to achieve a theoretical optimal combustion, an engine needs 14.7 parts of oxygen by mass to 1 part of gasoline (again, by mass). This is referred to as a stochiometric (chemically correct) mixture, and is commonly referred to as a 14.7:1 mix. If an engine burns with less oxygen present (13:1, 12:1, etc...), it is said to run rich. Conversely, if the engine runs with more oxygen present (16:1, 17:1, etc...), it is said to run lean. Today's engines are designed to run at 14.7:1 for normally cruising, with rich mixtures on acceleration or warm-up, and lean mixtures while decelerating.

Getting back to the discussion, the reason that exhaust valves burn is because the engine is burning lean. Normal engines will tolerate lean burning for a little bit, but not for sustained periods of time. The reason why the engine is burning lean to begin with is that the reduction in backpressure is causing more air to be drawn into the combustion chamber than before. Earlier cars (and motorcycles) with carburetion often could not adjust because of the way that backpressure caused air to flow backwards through the carburetor after the air already got loaded down with fuel, and caused the air to receive a second load of fuel. While a bad design, it was nonetheless used in a lot of vehicles. Once these vehicles received performance mods that reduced backpressure, they no longer had that double-loading effect, and then tended to burn valves because of the resulting over-lean condition. This, incidentally, also provides a basis for the "torque increase" seen if backpressure is maintained. As the fuel/air mixture becomes leaner, the resultant combustion will produce progressively less and less of the force needed to produce torque.

Modern BMWs don't have to worry about the effects described above, because the DME (car's computer) that controls the engine will detect that the engine is burning leaner than before, and will adjust fuel injection to compensate. So, in effect, reducing backpressure really does two good things: The engine can use work otherwise spent pushing exhaust gas out the tailpipe to propel the car forward, and the engine breathes better. Of course, the DME's ability to adjust fuel injection is limited by the physical parameters of the injection system (such as injector maximum flow rate and fuel system pressure), but with exhaust backpressure reduction, these limits won't be reached.

So, now we (I) know and will adjust posts acccordingly!

Ya got the part numbers for the muffler bearings by any chance ?

DV

[Excaliber]

Well that was an interesting reference Ed, good post with a nice balance between the myth and the facts.

Sounds like you would have to run the engine for some time before a valve burned, I'm not sure how long that would take. It reminds me of running unleaded fuel and burning a valve designed to run with leaded fuel. Yes, you could burn a valve without the lead IF you ran down the highway at sustained cruising speed for many many miles. Perhaps several hours.

I suspect a larger concern, and this may be an oft repeated myth, is cold air entering the exhaust chamber and warping the hot valve immediately after shut down?

[4RE KLR]

When I started mine, with the headers and no side pipes I could still see the flames coming out if the headers.

I would NOT recommend starting without the headers.

[Excaliber]

I think it's safe to say the thread originator has been sufficiently "frightened" as to not start the engine without at least the headers in place.

BUTTT, I'm still wondering, "What's the real problem if he did?" It's unlikely he would run the engine long enough to burn a valve, due mainly to the great noise (a very valid concern with hearing any knocking or other bad engine noises). Other than the noise factor in running the engine long enough to see if it DOES fire up, idle, etc. why is this a problem?

Fire from the exhaust? OK, but that could be handled with proper planning. Cold air valve warp? Maybe, how long would you have to run the motor? How cold would the air have to be? Is it even a reasonable consideration for a short time frame? What could possibly go wrong (here, hold my beer and watch this)?

[trularin]

Is this a Darwin award thingy???

[Zoom This]

You will do severe damage to your valves by starting a motor of any kind without headers as tcrist noted. I ruined a Chevy motor when I was 16 by running around the neighborhood one afternoon without exhauist headers. If you value your motor, don't do it.

[mr0077]

Ernie, when I was 15 I did the same thing to my brother's Olds as Zoom This did...warped 7 of 8 exhaust valves and lost my summer job money rebuilding his motor after a 10 minute joy ride with the exhaust manifolds off and wired to the side...I found out it doesn't take long to warp valves, and it took him even less time to get REALLY PI$$ED at me. I thought I was at the end of my life...

[Excaliber]

Well were making progress. We seem to have it narrowed down to somewhere around "10 minutes" to "going around the neighborhood". This assumes you don't burn a piston (good tip Ed) by going lean before the valves get damaged.

So, keep it under 10 minutes, watch out for the fire, run it rich (that will make for even better flames) and fire that mother up!