340 headers vs. factory manifolds

[Alaskan_TA]

Great article. Going from the 340 manifolds to the best headers they had access to resulted in less than a 7 HP gain with the combination they had.

Headers are not worth the trouble in my opinion for that minimal of a gain for a street car.

[71chally416]

I never said that every car should have headers. I said I'd never go out of my way to seek out 40 YO iron manifolds. It's obvious if you look at the different combos on exhaust in that crate motor test that none seemed to make very much difference. Why is that? Probably because of the very small camshaft they used, .385/.410" lift - much smaller than a stock 340 cam. That limits both the operating range (notice it's 5400 RPM redline in the test) and the HP peak of the motor. I believe those crate motors also have 9 to 1 compression, so any comparison it would have to a high winding 10.5 compression 340 with it's healthier stock cam (if anybody even uses that antique 40 YO cam grind anymore?) is not really valid. It's only valid on THAT motor if anybody uses it. It's not period correct for any 70 Cuda or Challenger so.... 

The best test would have been the one they didn't do. They should have installed the headers on this motor as the last step in this article>
http://www.compcams.com/Community/Articles/Details.asp?ID=-738676943

That way you could see how much difference they really make in a stock motor with the typical bolt-on parts like a good intake and carb and cam, even though the cam they use is the same size, but just an updated grind.

So it's up to what you want. Stock performance or an extra 110hp with a few bolt on parts. I think it's worth it for 110hp that never needs the bottle filled to use.     

[bb71challenger]

I like headers but I am stuck inbetween 2 different places. I have a set of shorty headers but they were rubbing on the engine bay. No big deal until I got it painted, now its not an option to have little or no clearance between the primary tubes and the inner fender. I am either going to cut and reweld the set I have which I modified with ball flanges and O2 sensor bungs, or I am going to blast and use a set of HP manifolds. The bad thing is I set the exhaust up for a stroker motor which I dont have yet. I have a dual 3" exhaust system and way too little motor for it lol.

[340Challman]

Best ET: 11.57 @ 123 MPH through the manifolds;


http://www.fastraces.org/members/fastraces/fastraces.nsf/00000000000000000000000000000000/0a9b33b9ae13f00e8525728f00424bf8!OpenDocument

 

I'm with you Barry. If he can run those times thru stock exhaust, why hassle with headers, especially with a 4 speed.

[Alaskan_TA]

For any street car, I am a manifold guy all the way. I have owned street cars with headers, the floor under my feet gets hot, they hang up on speed bumps, they are in the way if you have to replace a starter or steering box & on & on.....

Headers are just miserable, hateful things on a street car IMHO.

For a full out race car, different story.

It would be a cool experiment to see how fast Tom's car would go with open headers vs. through the manifolds & T/A exhaust system.

[Topcat]

For any street car, I am a manifold guy all the way. I have owned street cars with headers, the floor under my feet gets hot, they hang up on speed bumps, they are in the way if you have to replace a starter or steering box & on & on.....

Headers are just miserable, hateful things on a street car IMHO.

 
When my car had a 340, I went thru 2 sets of headers within 3-4 yrs. First set the low tube got smashed really bad. I first had 14" wheels on my car at the time. Then I switched to 15"s to bring up ride height. Still seeing that it was threatening to scrape on high spots on roads like speed bumps etc. I added leafs to the rear springs to help jack the angle up on the low header tube to lessen scrape point. Still seeing a scrape threat, I then welded a reinforcent metal on the suseptible low tube. Throughout the years while I had them, burnt wires, melted cable, cooked foot, constant re checking header gaskets.
Switched over to 70 manifolds and was way happier after that. I liked (and still do) to cruise for hours at a time so manifolds seem to be the answer for me.

[Topcat]

BTW, If still determined to run headers and want to loose the hot foot, this might be the answer. It's the highest heat reflective insulation material I've heard of. I saw a show on it and it's like a thick foil made by NASA originally for the space shuttles when coming in for re entry.

http://www.eagleshield.com/products-reflective.htm

[71chally416]

The "FAST" cars share nothing in common with typical restored muclecars except external appearance (if you don't look too close)

[moper]

Headers, as part of a balanced package, will make drastically more power, from idle to red line, on every engine they run on. Period. The key is the package. Stock engines with no mods dont rely on the characteristics that headers create on a performance engine. The fast cars are not a good example of anything but tenacity for detail and huge check books. If one were to disassemble a FAST car, not just the engine.. but the whole car, you'd see nothing is what it seems, and if headers were used, they would be FASTER cars..lol. It still boils down to the owner's choice. But for anythign that I need to make power on the street, or do better at emissions, or get better milage, I put headers on it and set the engine up to take advantage of them.

[71chally416]

This article/research appears to be outdated (2001).  HP2's link seems to provided current information.

You'll notice the same guy (Steve Dulchich) did both tests. The difference was one motor was a rebuilt HP 340 like a typical Cuda or Challenger owner would have and the other was a garden variety low compression undercammed 300hp  budget crate motor (Think "Goodwrench 350") that they wouldn't. Of course headers will make more difference on a higher compression motor with bigger valves and cam and a better Intake and carb. That's a no-brainer.

I linked a new Charger Hemi that knocked a half second off the ET with just headers and cat-back exhaust (NO OTHER CHANGES) when this header topic came up before. That's about as current as there is, and with 5.7L (345 cubes) and a comparable stock exhaust system to the old E-bodies (probably even better...) it is indeed a valid comparison

As a disclaimer I should mention that HotRod magazine bolted a supercharger on a late model GTO test car and went the same exact time they did without it, so your results bolting on any performance part may vary according to your mechanical expertise 

[priderocks]

Thanks guys for your input. Alskan T/A, I think I agree with you. I am going with the original manifolds. I will not run this combo hard enough to ever notice the minimal hp gains headers would give. I assume the factory mainfolds might also be a little quieter. Plus, I do like the stock look. Plus they are already paid for. Thanks again.