Help me justify a new exhaust to the wife

[Entropy]

Hey all,

Been doing a LOT of work on my K5 lately to get it good and safe to drive. Most of it has been front end and brakes. A big reason for doing it all now is that I have to drive it about 2000 miles because we are moving in less than two weeks. Which brings me to the current exhaust system.

Right now, it's single pipe and only 2" diameter after the muffler. There's nothing obviously wrong with it besides the fact that it's way undersized - no leaks that I can see or hear.

I can get a new dual-exhaust put on with flowmasters from the manifold back for about $450. Money is a little tight considering what's been spent in other areas already, but I'm thinking I can make an argument on gas mileage alone. I get about 9 currently - the problem on the highway, of course, is there is no overdrive and the gearing means the engine runs at pretty high RPM even at 65. If dual exhaust can add one or maybe 2MPG, then I can justify the cost in terms of gas savings for the trip.

Any idea if that is reasonable for going from a single 2" to dual 2.25" for a stock 350?

 

[AJs72K5]

I think that's gonna be a tough sell. Especially with a straight face. I don't think you'd have an appreciable mileage gain going duals.

 

[bp71k5]

Yea, what kinda motor you got that gets 9 on the highway? I hope its a big block, and if it is, 2" pipe is pretty restrictive so a better exhaust might help.

If it's a small block, you probably could spend the money on a tune up instead. I was getting 15 with a 327+th350 on the highway with mine. But I did have highway flier 3.07 gears.

 

[4X4HIGH]

A single 3" exhaust will be much better for mileage and low end torque.

 

[dbreid]

A single 3" exhaust will be much better for mileage and low end torque.

I just took my K30 from duals down to a single 3" with a Y pipe (I had the shop build me a disconnect fitting so I could still take out the transmission if I wanted without cutting everything out...) and the difference is noticeable. It isn't as quiet as I had hoped for, but it sure woke the truck up! I did it primarily for low end torque, but the power seems to be there throughout the band. Granted, this is just "seat of the pants" dyno, so maybe I am imagining, but it seems good.

-Dan

 

[Entropy]

Yea, what kinda motor you got that gets 9 on the highway? I hope its a big block, and if it is, 2" pipe is pretty restrictive so a better exhaust might help.

If it's a small block, you probably could spend the money on a tune up instead. I was getting 15 with a 327+th350 on the highway with mine. But I did have highway flier 3.07 gears.

It's a bone stock 350 (original quadrajet 4-barrel) with a 4-speed manual (SM465) and 3.73 rear end. I just looked up a calculator and at 65mph the engine will be about 2500 RPM and 80mph at 3000rpm which doesn't sound so bad. I don't have a tach, so I've only gone by the way the truck sounds and feels driving at highway speed - and it feels fast and loud!

I just did a tune-up and it runs pretty well. I haven't checked the gas mileage in a while actually. It hasn't been driven a lot for a few years and I have 33" tires now, which throws the speedo off.


4X4High,

Thanks for the 3" single pipe tip. I checked and that would be about $100-$150 cheaper than duals to boot.

 

[Greg72]

Stop driving 80MPH and you'll get plenty of MPG improvement.

It's hard enough pushing the K5 "brick" through the air at 65.... at 80 you can bet that engine is working a lot harder and drinking a lot more dino juice.

 

[RGV72BLAZER]

If lies are game, just tell her the fumes are coming into the cab, which on a 2K trip will eventually cause dizziness, nausea, and vomiting...which in turn will cause an accident. If not, save the money, take the wife out for a really nice dinner when you settle in, then spend the rest on doubler parts

 

[70jimmy]

Tire size change throws the odometer off also. The odometer is based on rotations of the tire (stock size) to make a mile. So to get a fairly accurate figure on mpg you would need to use traveled miles like mileposts, distance between cities off a map etc.

 

[Entropy]

Stop driving 80MPH and you'll get plenty of MPG improvement.

It's hard enough pushing the K5 "brick" through the air at 65.... at 80 you can bet that engine is working a lot harder and drinking a lot more dino juice.

True enough, but I can't remember the last time it ever was at 80. 65 "feels" about right as far as max speed goes.

If lies are game, just tell her the fumes are coming into the cab, which on a 2K trip will eventually cause dizziness, nausea, and vomiting...which in turn will cause an accident. If not, save the money, take the wife out for a really nice dinner when you settle in, then spend the rest on doubler parts

Nah, can't lie to the wife - she sees right through me even if I tried!

A doubler would be REALLY nice, but might be a bit beyond my skill level.

 

[RGV72BLAZER]

trust me, it's not...very intimidating at first but not much to it. I still surprise myself that I rebuilt my own 203 w/out instructions...let's just hope it doesn't fall apart . where in TX are you? I'd be willing to lend a hand...I got to Houston quite often...and SA/Austin every once in a while.

 

[AJs72K5]

If he's moving 2000 miles away, he's not gonna be in Texas anymore

 

[RGV72BLAZER]

maybe if he's moving from the tip of the panhandle down to Brownsville... didn't even notice that. but surely there's a CK5 member that'd be willing to help...

 

[Entropy]

Haha, yeah, I'm in San Antonio now, moving up to Ohio with some sidetrips and visiting on the way. I'm also moving from a car port up to a 1 car garage! Man do I miss having a big garage, but at least it will be inside now.

 

[Entropy]

Turns out I didn't need to sell it - got the spouse approval. Single 3" pipe going in tomorrow.

 

[4X4HIGH]

Turns out I didn't need to sell it - got the spouse approval. Single 3" pipe going in tomorrow.

You will be happy with the 3" single pipe. What muffler are you going to run, a flowmaster? I hope you like a loud exhaust, if not i would recommend a Gibson muffler. I run one and it has a nice tone and not too loud until you romp on it then it does get a little throaty. I believe mine is an 8" diameter something like 21" long. They are designed almost like a glasspack but not nearly as loud.

 

[Entropy]

That's a good tip. The Truck is already loud enough with the weatherstripping the way it is! I'll see what options they have in the morning.

 

[bp71k5]

To confirm what Scott said, I've got dual 50 series flowmasters (which as supposed to be quieter than the 40's) and the interior of the truck is much louder than the outside. It's cool for a few minutes, but I do get sick of the drone...