The Stovebolt Site Forums The Shop Area Engine Shop Does larger exhaust pipes increase power?

Hey guys, Got my 55.2 finally running for the first time- pretty cool. So now of course that Im happy, the wife is complaining about the noise (always something, right?). oh yea - it has no exhaust pipes or muffler at this time. So my question is it a good idea to increase the size of the exhaust pipes compared to stock. Will that by itself increase horsepower or screw up how the engine runs if that the only modification I make and keep the stock cam, lifters, intake & exhaust manifold etc? Very interested in your experience here since it time to buy the pipes & a muffler. Thanks

Shank

Forgot to include, engine is a 235 with single pipe

Helps top end hurts bottom end. I line 6 right? Maybe 2" max.

A 2" pipe with a flow through muffler at the end will let it breath and give good sound.

Anything bigger than 2" will have to be reduced at the manifold anyway.

Thanks. Yes its an in line 6. Any recommendations to muffler for this set up? Is flow thru the same as straight thru?

Shank

I would not use anything bigger than 2", You would find better results with pipe a little smaller than going bigger. I would get a generic round muffler. If you want a little rumble with your exhaust you could put a glasspack type muffler on.

This is the opposite end of the question: "will dual carbs improve the power on my otherwise perfectly stock 235"?

And the answer is basically the same: go back to the post by Hollow55, and reread.

Will probably give you more issues with trying to get a smooth idle. You might gain 5 HP at wide open throttle. How often will you be at wide open throttle???

Since you mentioned the wife is currently unhappy with the noise, and you aren't making any additional engine mods; would suggest going with stock exhaust.

(Opinion) MUCH better to impress the wife that you listened to her concerns than to impress the 15-year-old across the street with the noise!

Jon.

I'm with Jon!

When I was a younger man the motto used to be "If it's too loud, your too old." Well guess what......

I run 3" and have the equivalent hp of 6 of your motors

Because I am cheap. I used the front pipe from the ex manifold to the muffler. It was there and in good shape OK? The muffler came from some Hot Rod project that got new headers and pipe so it was just under the bench and in the way. It had 2 1/2 in and out so I added a reducer bit from Autozone and the up and over bent part fit rather well. So with 2 clamps and that reducer, I spent less than 20 dollars. It sounds OK, it fits, and now you tell me I gained some HP? Cheap is good. Maybe less than Hollow65 but I will take what I can get.

no Steve, because you used the stock diameter head pipe, you don't have any gain, just effectively shorter

Bill

:(, that sucks

Appreciate the feedback guys

Shank

To really gain hp, you need to put more air into the engine. As it is now, the exhaust is not the restriction point.
You will need to start with the intake ports in the head to free up some air movement, then the intake manifold and carburetor.
Now you have more coming in, but the camshaft is still stock, so it now limits how much air can fill the cylinders. At this point you change to a cam with more lift and duration.
Great, the motor now has all the fuel and air it needs, only the exhaust won't let it out. While cutting on the intake ports, you might as well open up the exhaust ports and add bigger valves.
This in turn means a bigger exhaust manifold is needed. Can't find one, go to header style manifolds, and now, finally you need bigger exhaust pipe. But wait, you didn't increase the rpm in which you drive most in so you still have the same hp and probably less torque then you started with. Not until you raise the rpm, will the extra power come into play.

Joe

Insightful - makes a lot of sense to see the whole package. Thanks!

Turbo?

Great post Joe. You have just made it real easy to just leave everything stock.
If these engines cannot be revved up to the level where they would show any benefit of the high performance modifications, then what's the point?
Carl

Quantify "equivalent hp." 1955 235 = 123 horsepower.
123 hp x 6 motors = 738 hp

Just curious.

Brad

the best way I can think of to increase horsepower is turbocharging, which would also have the benefit of being fairly quiet. I haven't done it yet, but I have one on the list.

Claud, I dynoed 741 at the crank. It is stupid fun... Maybe 580 at the wheels after the th400 and 2 piece driveshaft soak up a little. Nothing like a 60mph rolling burnout. Yes I am immature. We're all big kids playing with our trucks.

OK- gotcha, Hollow... you're not talking about a 235.

But the burnout does sound cool- enjoy it if'n you can afford it!

Still a kid, too.
Brad

Brad, I believe 65 has never even seen the inside of a stovebolt engine, and apparently never intends to. We have an arrangement where together we can pass everything on the road. He passes all the cars with his hotrod, and I pass the gas stations with my GEO Metro!
LOL!
Jerry

You're right Lincoln, I probably won't see the inside of a stovebolt. My heater actually does quite well with mpgs. Roughly 18 on the highway.

A video of you and the "60mph rolling burnout" would be an impressive argument for going to 3" exhaust pipes; should someone ever stumble on this thread & take it out of context. I can see it posted now:

gulliblespeedjunkie
New Guy- moderated

hey all this is my first post. i love this site but i read if i put on them three inch pipes out my 235 i'd have bout 700 horses under the hood. that dog dont hunt cos my 0-60 speed turned into 0-45 speed...is it the gas I'm running? do i need to grease the rear axle?

All in good fun
Brad

ho-hum

It is boring to read about a high-performance unknown power plant in an unknown vehicle in a forum about "normal" engines in pre-73 Chevrolet trucks.

It is less interesting than learning about an Advance-Design truck with a diesel engine producing 505 horsepower and 885 pound-feet of torque and it has 8-inch stacks ?

Ah, but, the original question was about larger pipes; so, this is still on topic?.

Did the stack increase power?

The "8-inch stacks" are necessary on the diesel to carry away all of the black smoke from the diesel!!!

A smaller pipe would quickly be stopped up from the pollution!!!

Do the diesels still have the tap on the bottom of the stacks to draw off the carbon, now that computer software has dramatically cut the demand for pencils?

Jon.

18 gallons per mile?

Jerry

The first restriction is fairly difficult to reduce: the relatively small volume in the exhaust manifold when the exhaust valve opens, since it's already pressurized by the previous cylinder's exhaust strokes.