Exhaust System

[goodnigh]

Installed a new exhaust system.

The old system had straight pipe

structure, no "curves", just a pipe.

The new system has several bends

and deflections which seem to serve

no purpose, or do they?

I can say the engine's performance

has changed much to the positive.

Crap, have to learn how to drive this

car again. There IS a difference in

pedal response. And it sounds

The picture of a tailpipe is representative

of the rest of the system.

mike

 

[mustang7173]

Hello goodnigh,

I would say that the new pipe created some back pressure that helps in scavenging the exhaust gases from the engine.

mustang7173

 

[jeff8877]

Mike,

What system did you go with for your car...have been looking at them for my 73 Mach 351C 4V...looking for nice sound and an increased pedal response would be great.

Jeff

 

[Mister 4x4]

Wow - looks like some of those bends got smooshed pretty good - probably dropped the overall diameter in places, which would restrict flow slightly and create that back-pressure.

Normally, you don't want something like that (pipes should be uniform diameter - even through the bends), but in this case it sounds like it's good for the engine. Maybe your original set-up was just a little too free-flowing, eh?

Glad it worked out for ya! ::thumb::

 

[goodnigh]

Mike,

What system did you go with for your car...have been looking at them for my 73 Mach 351C 4V...looking for nice sound and an increased pedal response would be great.

Jeff

Contact Don of OMS, a site vendor. www.ohiomustang.com

The car has a different sound and "snappy" pedal.

mike

 

[mdan575]

Unfortunately an exhuast is a very particular animal. Depending on the engine and the use free flowing is not always the best thing. Look at alot of cars and you will see pipes range alot in diameter. Back pressure does have its uses. Unfortunately car makers have engineers who can spend alot of time figuring this stuff out. But they also balance cost, fuel efficiency and a host of other things to. We are not so fortunate.

 

[goodnigh]

Hello goodnigh,

I would say that the new pipe created some back pressure that helps in scavenging the exhaust gases from the engine.

mustang7173

Not that long ago some forum members lambasted my mechanic

for extolling the virtues of back pressure in the exhaust. The picture

is the tailpipe. Bends also present in H-pipe and connecting pipes.

The engine is a quench 351C 4V with a "mild" cam and 770 Holley.

Don got it right on this setup.

mike

 

[72HCODE]

the bends are basically for ground clearance in areas like the center of the car so you don't get hung up on a speedbump.

the bend in the back is clearance over the axle and is different if you have a staggered rear shock setup because you need clearance for the sway bar back there also.

back pressure increased so you get much more throttle response on the bottom end under 3000rpms. it can also cause a effect where it feels like timing gets retarded about 1-2 degrees basically the engine richens up across the throttle curve. so you get more low end power and more drop off at higher rpms. with the open straight pipe exhaust, the engine would be lean, flow too much exhaust be ping happy or sluggish off the line then after 3000rpms it opens up. great for drag strip with a high stall convertor, bad for the street, unless you have a deep rear gear ratio that forces you above 3000rpms all the time.

there is also a sonic aspect to the bends in the pipes. sometimes they tune the pipes to knock down resonance at some rpms ranges.

cars after 1974 had resonators but the early cars didn't. this would produce a drone in the system so they would add bends in an effort to cut resonance at certain frequencies.

 

[Steven Harris]

Glad to hear the good report Mike.

It all looks very similar to what I have to put on mine.

What type of muffler did you use?

 

[OMS]

Wow - looks like some of those bends got smooshed pretty good - probably dropped the overall diameter in places, which would restrict flow slightly and create that back-pressure.

Normally, you don't want something like that (pipes should be uniform diameter - even through the bends), but in this case it sounds like it's good for the engine. Maybe your original set-up was just a little too free-flowing, eh?

Glad it worked out for ya! ::thumb::

Eric, that is old school hand held / loaded into the machine - mandrel bent just like the factory pipes in 1971

That particular system is duplicated from a original 71 Boss 351 exhaust system he has at the shop.

 

[CZ-75]

Do I spy a Miller High Life?

 

[Mister 4x4]

Eric, that is old school hand held / loaded into the machine - mandrel bent just like the factory pipes in 1971

That particular system is duplicated from a original 71 Boss 351 exhaust system he has at the shop.

It looks like some of the bends I tossed out when using a Bend-Pak machine to make the 'stinger' for my Jeep's bumper (took me 3 times to get it right - crease-less bends).

However, I'm not knocking it in the least - proof is in the pudding. Or in this case, the gas pedal. Nice work, nonetheless!

 

[goodnigh]

Do I spy a Miller High Life?

Actually MGD and that is the sizing standard here.

mike

Glad to hear the good report Mike.

It all looks very similar to what I have to put on mine.

What type of muffler did you use?

It is called a "Precision Performance Muffler" on the invoice.

mike