What's new
CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.

Straight pipes and valves

CherryK5

CherryK5

1/2 ton status
Joined
Jul 3, 2010
Posts
1,340
Reaction score
2
Location
Austin Texas
Is running straight pipes REALLY bad for your valves, or any part of your engine for that matter?

I keep seeing the "its bad for your valves.. cold air sucked in... blah blah... well thats what ive heard"

theres always the "thats what ive heard"
 
Maybe running without manifolds or headers...even so how does the cold air get there, and how does it stay cold enough to do anything detrimental? Last I checked exhaust flowed away from the engine, you'd think that "cold air" would have to be damned determined, and well insulated to flow the wrong way up the exhaust and straight to your valves...

I say BS.

Rene
 
tRustyK5 said:
Maybe running without manifolds or headers...even so how does the cold air get there, and how does it stay cold enough to do anything detrimental? Last I checked exhaust flowed away from the engine, you'd think that "cold air" would have to be damned determined, and well insulated to flow the wrong way up the exhaust and straight to your valves...

I say BS.

Rene
Click to expand...
Well engiine off one would assume..


When air cools it condenses and "sucks" up through the exhaust... well thats what ive heard..

haha
 
i've heard that too, i have seen a truck w/fresh set of headers that wouldnt idle, but as soon as the exhaust was hooked back up it idled just fine. what it was doing, i dont know, but it was doing something the motor didnt like.
 
OK, lets say you shut down your straight piped engine. The pipes are still hot, as is the engine. Again you need some super insulated cold air to flow up the length of the hot pipes...

Another thing is air is lousy for quickly quenching heat out of something, and "ambient air" is truly pathetic. Compressed air is OK but even that has nothing on a pint or so of water.

Open headers have almost no back-pressure, so unless a motor is tuned and jetted for it you will likely have idle issues.

Rene
 
I have ran my daily drivers with just manifolds and another with 2' pipes, no problems. I have ran an engine with no exhaust manifolds either. Air temp was about 60 degrees. I think it is a myth.

Most street engines run better with mufflers too.
 
god i love ck5.

We should be on mythbusters.


Well it does seem a little more responsive with 2.5 straight pipes than with headers. but not as good as my ghetto fab exhaust. time for some pepboys cheapo mufflers

Here's how mine is run, didn't take one of the pass side, but i will tomorrow or something.

CIMG0025.jpg
 
i burnt an exhaust valve due to a bad leak at the exhaust manifold. so i think it has merit
 
I call bs too...most competition engines run open exhaust, its a matter of tuning the engine to run that way. If you take a street tuned engine with stock type full exhaust and run open headers it will run lean, and possibly burn a valve or piston that way, but sucking up cold air to "burn"????? a valve? I Don't buy it.
 
well if anyone has ever seen a small block with just manifolds on it at night you can see the cost blue flame coming out of the manifold, i highly doubt any cool air is getting passed that lol.

i ran open mainfolds for awhile and never hurt anything except my ears.

just curious what is this goin to be in
 
Engines like 2 have at least a slight backpressure to help in scavenging exhaust gases and equalize exhaust pressures across all cylanders.at least thats the way I learned it from my shop teacher thats been building and racing cars 4 at least 40 years.he said for every foot of the header or manifold,u should have double that at least 2 give the engine the right amount to breath.so for 2 ft long header 4 ft of strait pipe or 2 a muffler is needed.ive always done this.i ran open header once just 2 the muffler shop and the engine ran bad,so I belive it.ive heard it can burn the exhaust valves after extended periods because the fuel flows through faster and the extra oxygen can richen the mixture making it hotter.its never happened 2 me.but open headers are loud and illegal 2 run on the road,so ive never done it for an extended amount of time.
 
it comes from people removing a stock (possibly single) exhaust system, putting on headers, then running the sh!t out of it without adding some fuel to the mixture.

look at some mid 80s exhaust manifolds on 3/4 ton and up chevys and fords. they have tubes that inject air from the a.i.r. pump directly at the back of the valve (they actually stick out of the manifold and down the exhaust port). if burning a valve was possible i doubt they would do that.
 
The only way you can damage anything is if your engine is tuned for a full, probably restrictive, exhaust system, and you then open up the exhaust. You can create a lean condition that causes heat and you can burn a valve.
I hate it when people say that you will "suck a valve". It only shows that they have no idea what they are talking about.

Engines DO NOT need any backpressure at all. It is about velocity, and creating low pressure/ partial vacuums behind the exhaust pulses to help pull out the next one, which is known as scavenging. However this is a dynamic phenomenon. It works differently at different rpm ranges, just like airflow coming into the engine. So the idea is to maximize scavenging while minimizing restriction, and here is the key, at the rpm range that you intend to use the engine.
 
I always thought this was a saying for the cooler weather climates and running headers only, no pipes, and not so much burning the valves while the engine is running, but people being more paranoid about the cold air going back up the headers when the engine is off and essentially cooling the valves off too quickly. Then firing it back up a short time later with cylinder temps still on a hotter side.

I dunno, I had a burnt valve issue in an old 4 cyl Datsun pick up truck a long time ago, not sure what ever caused it, we did have an exhaust manifold leak/crack, but I really don't remember what cylinders it was near or if that was even the reason for the problem.

I really don't worry about it though, I don't run open headers or exhaust systems without mufflers anymore. too old for that sheot.. :D
 
Straight headers with turndowns + motor running rich = ticket in high school by our SRO for throwing 2 foot flames in the parking lot
 
Well i doubt the motor will run lean, it has a 650 edelbrock with 700 cfm secondaries. But the plugs are showing fine so i run it, it smells like raw fuel when i stomp it and let off but i think that's normal. No pops or cool flames though.

Anywaysss, thanks for all the help guys!
 
You must log in or register to reply here.

Latest Posts

Top Bottom