Chevy Nova Forum banner

1 - 8 of 8 Posts

·
Registered
Joined
·
34 Posts
Discussion Starter #1
When i purchased my car it had a glass pack and some hokey welded parts to it. I took it off and put 2'' straight pipes on the thing. Will having less back pressure make the motor run hotter? Anything helps.
 

·
Registered
Joined
·
2,600 Posts
Oh boy, here's a thread that can get out of hand and open yourself up to conjecture and ridicule.

I never understood where people came up with this back pressure thing, I really think it's confused with exhaust velocity. There's no such thing as a motor needing back pressure to run correctly, if there were how would one quantify how much was needed? There is no way, my FEELINGS are that a system that is too big can trap heat, the gas doesn't keep moving fast enough to expel correctly. Same as using headers that are too big for the heads, velocity will be low and result in poor scavenging.

These are my unscientific thoughts not facts so go easy on the flames.
 

·
Registered
Joined
·
3,895 Posts
Oh boy, here's a thread that can get out of hand and open yourself up to conjecture and ridicule.

I never understood where people came up with this back pressure thing, I really think it's confused with exhaust velocity. There's no such thing as a motor needing back pressure to run correctly, if there were how would one quantify how much was needed? There is no way, my FEELINGS are that a system that is too big can trap heat, the gas doesn't keep moving fast enough to expel correctly. Same as using headers that are too big for the heads, velocity will be low and result in poor scavenging.

These are my unscientific thoughts not facts so go easy on the flames.
No flames here. You're right on track.:yes:

When i purchased my car it had a glass pack and some hokey welded parts to it. I took it off and put 2'' straight pipes on the thing. Will having less back pressure make the motor run hotter? Anything helps.
There's only ONE way a "Free'er Flowing" exhaust system will make a car run hotter.......

It can (in the more extreme cases) make the engine run LEANER because it is able to move more air and thus requires more fuel. A leaner running engine will make more heat.

Another way to look at it is.....if the engine makes more power---it will make more heat.
 

·
Registered
Joined
·
1,167 Posts
A buddy of mine believes if you dont have backpressure you will mess up your exhaust valves? :p
He cursed me when i told him im gonna run the engine with nothing but headers, until i can afford someone to weld up my exhaust!!!
But its gonna sit in driveway till then, cause i dont need a noise ticket!
 

·
Premium Member
Joined
·
4,365 Posts
A buddy of mine believes if you dont have backpressure you will mess up your exhaust valves? :p
He cursed me when i told him im gonna run the engine with nothing but headers, until i can afford someone to weld up my exhaust!!!
But its gonna sit in driveway till then, cause i dont need a noise ticket!
We need a "scratching your head" smiley for this one. Have your buddy explain the physics behind this falicy.

On a separate note. If you can't weld, you can always get a pipe kit, such as Pypes X-Pipe kit and two muffers of your choice and dump it at the axle. you will be able do drive it for about $250 and have a good stainless exhaust
 

·
Registered
Joined
·
1,167 Posts
We need a "scratching your head" smiley for this one. Have your buddy explain the physics behind this falicy.

On a separate note. If you can't weld, you can always get a pipe kit, such as Pypes X-Pipe kit and two muffers of your choice and dump it at the axle. you will be able do drive it for about $250 and have a good stainless exhaust
I got a quote for $200 to weld up the exhaust, I just dont have the money just yet with the vacation next week, and those pesky bills... I just want to fire it up and break in the cam, then do the 500mile thing, and park it for the fall/winter to do the ground up restoration... so no hurry on the exhaust.

As to the exhaust idea my buddy has, i've asked him before on "why" and he stumbles with an answer and finally say something like "thats just what i heard"... BLAH
 

·
Registered
Joined
·
1,286 Posts
As to the exhaust idea my buddy has, i've asked him before on "why" and he stumbles with an answer and finally say something like "thats just what i heard"... BLAH

If you ran the engine without any headers or manifolds there would be a chance of ruining the exhaust valves but you should be OK running with headers on.
 

·
Registered
Joined
·
1,047 Posts
Oh boy, here's a thread that can get out of hand and open yourself up to conjecture and ridicule.

I never understood where people came up with this back pressure thing, I really think it's confused with exhaust velocity. There's no such thing as a motor needing back pressure to run correctly, if there were how would one quantify how much was needed? There is no way, my FEELINGS are that a system that is too big can trap heat, the gas doesn't keep moving fast enough to expel correctly. Same as using headers that are too big for the heads, velocity will be low and result in poor scavenging.

These are my unscientific thoughts not facts so go easy on the flames.
Dead On :yes: Your feelings serve you well,,may the force be with you:D

With tuned headers the primary tubing ID size affects the velocity of the exhaust pulse and the timing of the return negative pulse.I've had engines slow down after the pipes got hot :eek: when the primary ID was slightly on the small side.Small pipes look good on a short (20 sec) dyno pull but a few laps on the racetrack tells the tale.:eek::devil:
 
1 - 8 of 8 Posts
Top