Headers vs manifolds on a stock 454, observations - Chevelle Tech
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post #1 of 20 (permalink) Old Dec 14th, 17, 4:36 PM Thread Starter
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Headers vs manifolds on a stock 454, observations

I always wondered how much torque was added by switching from cast exhaust manifolds to headers, never had a car without headers already on. I recently did the change on my 79 C-30, and it far exceeded my expectations. These engines had a ~184/194 at 0.410 cam and 7.9:1 compression ratio, super mild and embarrassingly slow in stock form. I got really tired of the lack of torque and power, but was too lazy to pull the engine. I started by recurving the distributor, setting the Qjet correctly for best power, and yanking the smog parts. This was barely noticeable on the butt dyno, but helped. Next was ditching the OEM style mufflers, went with 20" Walker 2 1/2" turbos on the stock crimped up dual head pipes (dumps in front of the axle). I could feel the effect mid range, definitely noticeable but not really anything major elsewhere.

A few months later I noticed an exhaust manifold leak, so I removed them and installed a set of Summit headers and custom mandrel bent pipes. BIG TIME difference. Major improvement across the RPM range, off idle all the way up. I can now cook the tires from a stop, none of that before. WOT is like night and day, and the 3000 RPM cliff is no longer there. And, I went from 9 to 11.5 MPG on the freeway on 3.73 rear gears at 75 MPH. This is still with the stock cam, and the iron pancake intake. Next up is an aluminum intake, then 1.8:1 stainless roller rockers.

I'm very pleased with the bolt ons, the truck went from a gutless pig to drivable. I had seen some dyno pulls with manifolds on the old LS5 and 6 engines, you could tell there was some restriction and I guess that was it.
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post #2 of 20 (permalink) Old Dec 14th, 17, 4:41 PM
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Re: Headers vs manifolds on a stock 454, observations

Good info
Years ago,I picked up almost 5 MPH and almost 3 tenths in the 1/4 swapping from manifolds to headers with a well built 454

FWIW,there is a member on here (and good friend) "Big Block Dave" who took his stock,matching numbers 1974 454 4 speed Corvette down the track and ran a [email protected] MPH..bone stock,other than headers and sidepipes along with 3.55 gears.
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post #3 of 20 (permalink) Old Dec 15th, 17, 3:55 PM
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Re: Headers vs manifolds on a stock 454, observations

bunch of years ago, 25+ , a buddy bought a mid 70s C10 with a 454. if you didn't look under the hood you would swear it was a 305! first thing we did was headers and exhaust, night and day!
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post #4 of 20 (permalink) Old Dec 15th, 17, 4:16 PM
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Re: Headers vs manifolds on a stock 454, observations

Engines are only an air pump. If air goes in and cannot get it out it will not be efficient.
Take a deep breath, have someone grab your throat and squeeze some, there you have it and feel it.
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post #5 of 20 (permalink) Old Dec 15th, 17, 4:41 PM Thread Starter
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Re: Headers vs manifolds on a stock 454, observations

Quote:
Originally Posted by mark_follweiler View Post
bunch of years ago, 25+ , a buddy bought a mid 70s C10 with a 454. if you didn't look under the hood you would swear it was a 305! first thing we did was headers and exhaust, night and day!
Yep. I wanted to post this since there a quite a few people running these engines, and they usually get told to swap heads, cam, etc. Much can be done with the stock package, I was very surprised how much I picked up just by that change. You would think that teeny tiny FT would limit the gains. I'm sure it does but less than you'd guess.

I am going to try to get the 2_0 manifold on soon, to see what that does. Anecdotally 15-10 HP, but once again I've never swapped from an OE iron to an aluminum. Then I'm installing the 1.8 roller rockers. Supposedly the ratio is closer to 1.9 and also higher throughout the lift range compared to stock stamped units, so it ought to be like adding duration. We will see...

At that point there's no more bolt on fun, other than nitrous.
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post #6 of 20 (permalink) Old Dec 15th, 17, 5:00 PM
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Re: Headers vs manifolds on a stock 454, observations

The 2.0 manifold is a peanut port manifold


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post #7 of 20 (permalink) Old Dec 15th, 17, 5:19 PM
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Re: Headers vs manifolds on a stock 454, observations

I noticed a drop in performance when I got rid of my full length headers and went to exhaust manifolds on my 468 cruiser.

GenVI 454,Autogear M-22W,Moser 12 w/3.42s


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post #8 of 20 (permalink) Old Dec 15th, 17, 5:31 PM
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Re: Headers vs manifolds on a stock 454, observations

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Originally Posted by shovelrick View Post
The 2.0 manifold is a peanut port manifold
The 2-0 manifold is an oval port.

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post #9 of 20 (permalink) Old Dec 15th, 17, 6:22 PM
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Re: Headers vs manifolds on a stock 454, observations

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Originally Posted by oldcutlass View Post
The 2-0 manifold is an oval port.
It is an oval intake but the ports neck down to fit peanuts.
This is a 2-0 intake scribed to oval port.
An old cast iron high rise flows better.
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post #10 of 20 (permalink) Old Dec 15th, 17, 6:51 PM
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Re: Headers vs manifolds on a stock 454, observations

Is the 2.0 the same manifold as a 2-0 ?, I don't mean to hijack or anything but I'm a little confused, sorry about that, I had a 2.0 on my 454 and was told it was for peanut heads and when I pulled it off to replace it with a RPM AG the ports were smaller, they did match the pp heads I had on at the time, again I don't mean to side track the OPs thread but would like to clear it up before the OP might buy the wrong intake, rick, ps maybe the OP has pp heads


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post #11 of 20 (permalink) Old Dec 15th, 17, 8:21 PM
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Re: Headers vs manifolds on a stock 454, observations

OP you may also want to check cam timing, sometime in the late 70s or 80s they backed it off for emission purposes. There's power to be had advancing it to where it belongs.
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post #12 of 20 (permalink) Old Dec 15th, 17, 9:34 PM
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Re: Headers vs manifolds on a stock 454, observations

Quote:
Originally Posted by Stu1 View Post
I always wondered how much torque was added by switching from cast exhaust manifolds to headers, never had a car without headers already on. I recently did the change on my 79 C-30, and it far exceeded my expectations. These engines had a ~184/194 at 0.410 cam and 7.9:1 compression ratio, super mild and embarrassingly slow in stock form. I got really tired of the lack of torque and power, but was too lazy to pull the engine. I started by recurving the distributor, setting the Qjet correctly for best power, and yanking the smog parts. This was barely noticeable on the butt dyno, but helped. Next was ditching the OEM style mufflers, went with 20" Walker 2 1/2" turbos on the stock crimped up dual head pipes (dumps in front of the axle). I could feel the effect mid range, definitely noticeable but not really anything major elsewhere.

A few months later I noticed an exhaust manifold leak, so I removed them and installed a set of Summit headers and custom mandrel bent pipes. BIG TIME difference. Major improvement across the RPM range, off idle all the way up. I can now cook the tires from a stop, none of that before. WOT is like night and day, and the 3000 RPM cliff is no longer there. And, I went from 9 to 11.5 MPG on the freeway on 3.73 rear gears at 75 MPH. This is still with the stock cam, and the iron pancake intake. Next up is an aluminum intake, then 1.8:1 stainless roller rockers.

I'm very pleased with the bolt ons, the truck went from a gutless pig to drivable. I had seen some dyno pulls with manifolds on the old LS5 and 6 engines, you could tell there was some restriction and I guess that was it.
I ran my 75 C20 454 on a dyno back in July. The truck had around 53,500 original miles on it. The only thing not stock is an open element air cleaner, performance ignition module, coil and plug wires from Performance Distributors. Cast iron exhaust manifolds, 2" duals into generic turbo mufflers, turning out behind the rear tires. They did 3 pulls,

first pull.......228.6 [email protected] / 318.1 [email protected]
second pull...226.9 [email protected] / 320.8 ft.lbs @34 00
third pull......228.7 [email protected] / 323.0 ft.lbs @34 00

I was surprised at the HP numbers but I thought the torque would be a little higher than what it was. I did this to get a base line for some future bolt on mods and to see what kind of numbers I can get. First thing I did was the exhaust. It now has 1-3/4" full length tube headers, a 2-1/2" Pypes system, with an X-pipe into Dyno Max Ultra Flo mufflers, sounds killer.
I didn't get a chance to run it on the dyno after the exhaust change but it definitely made a difference. I plan on another dyno session in the spring when the weather warms back up to try and get an accurate comparison. I thought you would be interested in the numbers on basically the same motor.

Jeff
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post #13 of 20 (permalink) Old Dec 16th, 17, 3:17 PM
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Re: Headers vs manifolds on a stock 454, observations

Quote:
Originally Posted by BB68 View Post
OP you may also want to check cam timing, sometime in the late 70s or 80s they backed it off for emission purposes. There's power to be had advancing it to where it belongs.
Correct and that 70's era cam can be replaced in place without losing your A/C charge with a couple of bungee cords holding the condensor up and out of the way.So while you've got the manifold off you can just drain the rest of the coolant when you remove the W/P.Probably needed a coolant flush anyway.

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post #14 of 20 (permalink) Old Dec 19th, 17, 12:38 PM Thread Starter
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Re: Headers vs manifolds on a stock 454, observations

Quote:
Originally Posted by 72BB Nova View Post
I ran my 75 C20 454 on a dyno back in July. The truck had around 53,500 original miles on it. The only thing not stock is an open element air cleaner, performance ignition module, coil and plug wires from Performance Distributors. Cast iron exhaust manifolds, 2" duals into generic turbo mufflers, turning out behind the rear tires. They did 3 pulls,

first pull.......228.6 [email protected] / 318.1 [email protected]
second pull...226.9 [email protected] / 320.8 ft.lbs @34 00
third pull......228.7 [email protected] / 323.0 ft.lbs @34 00

I was surprised at the HP numbers but I thought the torque would be a little higher than what it was. I did this to get a base line for some future bolt on mods and to see what kind of numbers I can get. First thing I did was the exhaust. It now has 1-3/4" full length tube headers, a 2-1/2" Pypes system, with an X-pipe into Dyno Max Ultra Flo mufflers, sounds killer.
I didn't get a chance to run it on the dyno after the exhaust change but it definitely made a difference. I plan on another dyno session in the spring when the weather warms back up to try and get an accurate comparison. I thought you would be interested in the numbers on basically the same motor.
Absolutely, I'm curious to see what you see on the dyno vs my guesses. I'm thinking 50-75 ft lbs across the board and a 800-1000 RPM higher torque peak.
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post #15 of 20 (permalink) Old Dec 19th, 17, 12:41 PM Thread Starter
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Re: Headers vs manifolds on a stock 454, observations

Quote:
Originally Posted by 71350SS View Post
Correct and that 70's era cam can be replaced in place without losing your A/C charge with a couple of bungee cords holding the condensor up and out of the way.So while you've got the manifold off you can just drain the rest of the coolant when you remove the W/P.Probably needed a coolant flush anyway.
Good ideas, but it kinda violates the bolt on principal and is a big PITA to get the pan to reseal IMO. I would just pull the engine at that point. But, it's tempting...
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