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Headers on ebay

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WALTER

WALTER

Jedi Hopeful
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I would like to get input on the headers that were on ebay recently. I would like to put them on my BJ8 for the potential extra power. THe car currently doesn't have the two flex sections anyway and they are included. I have a second chance to buy them.

I attached a photo.

Thanks,
Walter
 

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Hi Walter, simply adding headers to an engine does not assure an increase in power.However, there might be a slight decrease in overal weight of the exhaust system..--FWIW---Keoke
 
Hi Keoke ,
If the air flying through the engine is less restricted, Isn't there a really good chance it will gain power?

W
 
Seems like they were poorly designed (or built), being modified that much just to fit. The question you may want to ask before you buy is will the collector fit a stock exhaust. My headers are for a 2" exhaust. You can step the diameter down, but there's not a lot of room to do so. Or maybe you're thinking of a whole new system.
 
[ QUOTE ]
Hi Keoke ,
If the air flying through the engine is less restricted, Isn't there a really good chance it will gain power?

W

[/ QUOTE ]

Hi Walter
Yes, but you have to look at the whole system. If you have a stock intake, stock mufflers, cam, etc, you're still flowing the same volume.
 
[ QUOTE ]
Hi Keoke ,
If the air flying through the engine is less restricted, Isn't there a really good chance it will gain power? ------------ Nope Walt, no body did anything to make the air fly through the engine and the headers will not do it alone.---Keoke /ubbthreads/images/graemlins/driving.gif


[/ QUOTE ]

Thanks for that Greg /ubbthreads/images/graemlins/thumbsup.gifKeoke
 
Thanks Greg and Keoke. Thats why I threw it out there. Going from two inch back down to 1.75 seemes to defeat the purpose. And replacing the whole system with 2 inch defeats the bargain. They sure are pretty though.

W
 
Well Walt, ifin they so pretty and the price is right you can hang um on the wall as garage art.---Keoke /ubbthreads/images/graemlins/cool.gif
 
Dennis Welch seems to think differently. On his site he says the headers will give the single biggest improvement in power for the money spent. (ok he's marketing, but isnt polishing and porting really about the same thing. Improving gas flow through and out of the engine.) The stock exhaust manifolds were very primative.

cheers
 
As with any flow system [in this case right from inlet manifold, through engine, exhaust manifold, silencer and exhaust pipe] either it has been designed perfectly or, more likely, there will be a single point of restriction somewhere. Only by knowing where this restriction is, and removing it, will any performance improvement result.

Rgds

Mike
 
[ QUOTE ]
Dennis Welch seems to think differently. On his site he says the headers will give the single biggest improvement in power for the money spent.

[/ QUOTE ]

That could be interpreted a couple ways (typical advertizing). /ubbthreads/images/graemlins/crazyeyes.gif The way I read it, once you buy your DCOE's, hotter cam, freeflow exhaust, multispark ignition, high ratio roller rockers, forged high compression pistons, pay the machine shop to skim the head and balance your ports, the price of the headers looks pretty good. On another note, at the top of the exhaust page on Dennis' website they say "All our exhaust systems are manufactured to the highest tolerances and specification". I had to cut out a portion of the collector and weld a flatter piece in to clear the pedal box. Also had to add 2" onto the end of one header to clear the outrigger. All that to say you can't always trust what you read when money is on the line. /ubbthreads/images/graemlins/cryin.gif

Best Wishes,
Greg
 
On a sorta related note.

I just re-installed my manifolds after having them jet-hot coated. Besides looking really clean compared to the rust bombs they were, the coating is supposed to keep the heat in. At any rate I am very pleased with the results at a fraction the cost of a header set.

Disclaimer-no financial interest etc blah blah
 
I bought into that for may MGB many years ago. The idea was to get equal amounts of exhaust out of each port and not creat eddies for a free flow. I also put on an Abarth sxhaust system. I found no imporvement except in sound.
 
Derek ,if I was selling headers I think I would think that way too.---Keoke /ubbthreads/images/graemlins/laugh.gif
 
Are we really knocking headers here?
The way I understand it: the way to make more power is to improve volumetric efficiency.
A good set of headers is designed to EXTRACT the exhaust from the combustion chamber, and as a result, help to move more volume though the cylinder. If the exhaust manifold is the weakest link in the exhaust, a good set of headers will pull more volume though the chamber, even into a stock exhaust, which could flow more than the manifold.
So, a good set of headers and re-jetted carbs would be a good place to start.
For what it's worth- the headers I bought for my BJ8 from DW fit fine. They lined up to the original type exhaust nicely but I went a step further and welded a section of the original type flex pipe to the header and had it Jet-Hot coated.
 
MH67,

Headers look good & sound good. Whether they help power or just make more noise depends on how restricted the original system is, AND on several other related items.

They can only let out what the rest of the engine lets in. "Extract" implies pulling a vacuum on the exhaust ports. Except in rare instances, headers cannot pull a vacuum on the rest of the system to increase the amount of flow into the engine. There IS such an effect, over a narrow rpm range, with some very highly tuned engines. Exhaust "extraction" on the average engine is just advertising hype. The Healey's exhaust is not particularly restricted in the first place.

To take full advantage of headers; the intake, port flows, cam timing, compression ratio, & exhaust ports all need to be changed as a balanced system. This all implies sacrificing some low rpm power to gain more at higher rpm. No doubt that headers on a stock engine look impressive & are fun though. Maybe perception IS reality.
D
 
I think I agree with Motorhead on this one. I understand also that the original exhaust manifolds are pretty primative and do restrict flow so they are a form of blockage in the system which headers help to alleviate. All performance engines use headers.

On the related and maybe more interesting point re the look and the sound. (we're all big kids really!). Yep they look good, particularly with the big bore side exhaust.

Regarding the sound, this is interesting, because the sound definitely changes but Im not sure its better. The standard Healey sound changes noticeably around 2500 rpms? to that distinctive Healey rasping sound. This doesnt happen with the headers..(evidence of freer flow?). The headers have a deeper rumbling sound all the way through the range. Not sure its better,,,I miss the rasping sound.

The other difference is resonance. the cast iron manifolds act as a big resonance sink. With the headers the resonance is very noticeable.

cheers ( & happy with headers...sort of! /ubbthreads/images/graemlins/driving.gif)
 
I find the original manifolds not bad as far as manifolds go. I and a few other Southern Californians installed Kirk headers 20 plus years ago and noticed immediate improvements in mid range torque. The Kirk headers are much longer than the Welch/factory team style. For racing, I would use the Welch items.
 
Hi Motorhead,
I don't think anyone is dissing headers. I'm just saying that to realize the full potential of the headers, you need to modify the engine and/or exhaust to how you want to use your car. This is my understanding of exhaust scavenging: When the exhaust valve opens it creates a positive pressure pulse, which goes out the tailpipe. When it reaches the atmosphere, the pulse reflects back to the valve as negative pressure. Each time it passes through the muffler, the pulse looses energy. The more restrictive the muffler, the greater the loss. When the negative pulse reaches the valve, it can pull exhaust gases out of the combustion chamber if both valves are open. This creates a low pressure in the combustion chamber which helps pull fuel/air mixture in. You need a cam with the right overlap to get this. The pulses move at a relatively constant velocity so changing the length of the pipes effects when the pulse returns to the valve. When you increase RPM, the valves open and close in a shorter period of time, so a valve that is open at a particular RPM range will not be open at another when the pulse reaches it. That’s what Dave is talking about. Hope this makes sense.

Best,
Greg
 
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