Engine in question is a 350 SBCwith a 327 crankshaft. I don't know of any other mods to the engine, which was running good when I drove the car it was in. It has 2" exhaust pipes and I was wondering, for a street car, if the cost of upgrading to a 2½" exhaust would offer any benifits to balance out the cost of changing it. I want to put it in my '36 coupe project, so there's a question of fitment, too. Any input wouold be appreciated. Thanks, -Bob
No not any benefit other than making it louder., plus 2.5 inch exhaust is gonna get real tight under a 36 ford. 2 inch is plenty for a mild or stock motor.
Unless you are racing or driving the car above 5000 rpm for long periods, you won't notice the difference between 2 in and 2 1/2 in exhaust. Spend the money elsewhere.
Moving to a larger diameter exhaust system on an engine, where the use-case does not cause an increase in exhaust gas volume, simply decreases the scavenging effect. Any decrease in the scavenging effect can lead to spent combustion gases being left behind in the combustion chamber, that would have otherwise been removed by the smaller system. This unregulated exhaust gas recirculation can foul the next intake charge, leading to a decrease in performance and mileage. I made tidy money in the 1990s taking dual 3-inch systems off of 350 equipped Chevrolet/GMC trucks, that ran poorly, and saw a loss of low-end torque, and a decrease in mileage.
I know we all like dual exhaust. However, I’ve often wondered how much extra performance is ACTUALLY gained from going to a stock type single exhaust, 2” head pipes to a 2-1/2” single with a stock type muffler, to dual 2” pipes with turbo type mufflers. This would be on a stock, or stock with a little cam, small block engine. I think many guys confuse more sound with more power. Obviously, on modified engines, this all goes out the window.
No one mentioned looks. I think over large pipes look wrong on traditional cars. Especially when not needed. JMO
I put 2.5pipes on my mild 327. Spent more time reworking them to fit and not hit the underside than the hoursepower gains I obtianed.
I have 2 inch in my 36 and it is tight like Nailhead Jason said. Now if you ran fenderwell headers you may use a short peice and mufflers run under the running boards
My rules over the years have been 2" for engines up to 383ci, then 2.25" for 383-427ci. Only using 2.5" on motors larger than 427ci and only then if they're performance motors. A motorhome with a 440ci Big Block only needs 2.25-2.50" exhaust since it's never under excessive RPMs. ~Peter
Hello, When my wife and I were looking for a station wagon or woody, we knew it had to have a v8 Chevy motor. We knew we were not going to race it, so steel custom made headers was not called for in the v8 motor scenario. My previous sedan delivery had an 80 hp Flathead and that was not going to do it this time. Although, the Flathead gave me thousands of reliable road trips, in various places, sometimes it was first gear going up the steep incline in the traffic lanes. In our teenage years, we took off the stock “y” manifold and put on several different steel header systems on different Chevy sedans. But, in looking back, the 57 Chevy Bel Air Hardtop needed some extra "oomph" and the Hedman Headers were easy to put on and made some good flow for more power. There were never testing areas where we could get certified results, but the smooth bends and flow of the exhaust would just make it seem like it does better than stock. Later on there were magazine articles that proved the smoother flowing exhaust pipes were better than the cast iron “y” manifolds. Jnaki Our purchase of a project 1940 Ford Sedan Delivery with a 327 for power was the starting point. It ran well through the stock “y” cast iron manifold and there was nothing to make us change the smooth running motor for all of our short and long distance cruising road trips. There was no need for larger pipes. It was smooth, quiet and gave us enough power to go up steep coastal hills and even into the higher elevations of the local mountains to 8,000 feet. So, if the stock “y” manifolds work for you, unless you are building a specific style or type with steel custom flowing headers, there is actually no need to change anything. It would seem large is better, but in the long run reliability and no need for worry about rusting through is a choice. YRMV
I stepped my system up from 1¾" at the beginning to 2" for the mufflers, then 2½" after the axle, tucked it all inside the frame. Holy **** that was a job. I may yet dimple a spot or 3 once fully mounted to ***ure no rattles. It's a fresh 239 flatty so why the 2" you might say. Because there was no way I was gonna do that job again if it got a SBC some time in the future. And as to why the big tails, it's the only exhaust you can see from outside the car and they're polished stainless.
Depends on your steering box and header design........2-1/2 inch pipe might not fit if you have the stock box.
That's what I was wondering about the 1 3/4". The system in my '47 is still in good shape and just in case for a 283 in the future I can just rework the head pipes.
That's what I did. I flange mounted from head pipes which extend to just about the back of the trans. I used a 1¾ ID to 2" adapter trying to keep transitions inside in flow direction. Not a that a stock flathead will notice. I used generic 2" Walker gl***packs which are probably not the best, but $48 for both vs others at $110 each, fine by me.
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