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Old 09-09-2011, 12:25 AM   #1
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Exhaust Manifolds vs. Headers

Need some advise on replacing my exhaust manifolds vs. headers. I need to replace the manifolds (87 Allegro w/454 big block - 60K miles), but what benefit, if any, would I get by replacing my manifolds with new headers instead?

Just need some insite to this.

Thanks
Arnold
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Old 09-09-2011, 05:01 AM   #2
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A good set of headers, will improve exaust flow and not get quite as hot, therefore, not as prone to warping. Banks makes a very good set of headers and gaskets, additionally if you add a free flowing exaust system from the end of the headers on back you will gain a little HP, and fuel mileage. This is a common problem with older motors with out fuel injection.
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Old 09-09-2011, 06:27 AM   #3
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When you read the claims of "Up To" so many HP. Keep in mind it means if you change the cam, carburetor, intake manifold, muffler, compression, etc, you might see that "up to" HP.
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Old 09-09-2011, 06:59 AM   #4
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I had put a set of headers on my old 454 (carburetor) engine. I had to throw them away because they kept burning out spark plug wires- too tight on clearances of plugs and wires (they were "Redmonds", or something like that).

I then put on Banks headers and no more problems.

They are louder in the cockpit than original cast iron exhaust manifolds.

The difference in power was immediately felt. Never noticed much improvement in MPG.

Good luck,
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Old 09-09-2011, 07:12 AM   #5
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Haven't seen a set of headers since, well lets just say a long time ago. I must say at the very least headers will make your rig sound great. I miss those days when fast cars sounded powerful, not like a sewing machine on steroids.

Heat wise I'm not sure about for an RV application but back in the old days some hot rod cars had heat proof fiberglass (I think) tape on the headers to shed the heat from the engine back toward the exhaust.
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Old 09-09-2011, 07:33 AM   #6
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I think Taylor makes hear-proof plug wires.
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Old 09-09-2011, 07:57 AM   #7
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May I ask why you need to replace the exhaust manifolds?
Are the cracked? Or are they just leaking?

If they are not cracked, replacing the gaskets at the heads and new donut gaskets at the pipes should solve any leak issues.

The passenger side manifold on these older 454's are prone to leaking. I have one, I know. My biggest issue is the donut gasket - bolts wiggle loose (even with doubles nuts) and leak.

Don't spend money you don't have to. It is a tight fit, but you can replace the gaskets yourself with the motor in the RV, usually.
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Old 09-09-2011, 09:50 AM   #8
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Yea I have one that is cracked and the previous took the smog equipment off, but didn't do it correctly (just bent them over). Thats why I'm replacing them. I'm having my mechanic do it because I don't have the expertise to do that type of work and he has quoted me a very reasonable price for that and other work. Just wanted to get some input.

Thanks
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Old 09-09-2011, 11:06 AM   #9
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Take it to a performance shop, one that actually builds race cars, street cars, and engines. The right headers and exhaust, with some carbeurator adjustments, timing and fuel flow can make all the difference in the world if done correctly. We had the complete Banks system on our '05 Winnie (8.1 vortec) and, even though it did make a difference, it wasn't worth the money. I took it to a "racer guy" who did his thing and man, what a difference. There all kinds of header products and spark plug accessories to deal with the heat issues now by the way. And yes, it does sound way cool when you're done!
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Old 09-09-2011, 02:09 PM   #10
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Quote:
Originally Posted by HD4Mark View Post
Haven't seen a set of headers since, well lets just say a long time ago. I must say at the very least headers will make your rig sound great. I miss those days when fast cars sounded powerful, not like a sewing machine on steroids.

Heat wise I'm not sure about for an RV application but back in the old days some hot rod cars had heat proof fiberglass (I think) tape on the headers to shed the heat from the engine back toward the exhaust.
Wrapping headers is good for hot rodders, but DO NOT PUT HEAT WRAP ON ANYTHING DRIVEN MORE THAN 1/4 MILE AT A TIME!!

I speak from horrible experience-- years ago I put a set of Hooker headers on our '78 Cruise Air's Dodge 440. The reason for the change was that someone had changed out the left side manifold with a car-style, which was taller, which was causing the dog house to melt! Because of the melting, I thought wrapping the headers would be a great idea.

It was, for about 500 miles. At that time, half way to Tahoe on vacation, I had a quarter-size hole blow out of one pipe right at the top of the first bend, about 2" from the head. I had plenty of tools and was able to make a reasonable patch. Less than 100 miles later, 2 more holes blew thru... It became painfully obvious the problem was the heat tape-- it was insulating the head pipes at their hottest points from air-cooling, and the heat quickly disintegrated the pipes...

I replaced the with another set of headers, which went several years without issue...

I did notice a bit more power on the hills--
They did seem to keep the engine bay cooler--
Not one bit of help in the gas mileage department!

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Old 09-09-2011, 03:25 PM   #11
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I don't know about now, but Hooker headers used to be about the bottom of the line for quality. Poor man's headers, so to speak.
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Old 09-09-2011, 08:02 PM   #12
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If you go with the headers. Get them coated with a product like Jet-Hot, which will provide a performance bump and a temperature reduction
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Old 09-09-2011, 09:35 PM   #13
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I have a set of Thorley headers on the 8.1 GM with a custom fab exhaust. Much lower temps, better flow (along with the banks air box) better power but not much increase in fuel economy. I try to not pay attention to the mileage. For a car it get really poor fuel economy, but great mileage for a condo !

If you have to spend the money for the labor, go ahead and do the headers as well, but spend the right money on good product as you pretty much get what you pay for.
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Old 09-09-2011, 11:44 PM   #14
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I talked Doug into selling me headers for my Dodge Ram 5.9L gasser before they were in production. If I heard right, he designed headers for a major company before going off on his own.
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