When should I add headers?

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Anonymous

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Has anyone calculated the maximum intake allowed before the stock exhaust manifold becomes the restricting factor (assuming the log is divided into two partions)? What is the intake vs. exhaust flow rate?
If I'm pulling in 1000 CFM how much should I be exhausting?



-Chris
 
u should add headers...even with a stock system its a good idea because the breathing ability of the inline really sucks...so headers would definitely be a good thing if u are pulling 1000 CFM
 
I know I should add headers but it would be cheaper for me to add carburation than headers and carburation. I just wanted to know the limits for a basically stock 200.


-Chris
 
depends...a 1bbl carb would be cheaper but wont give u the CFM u want...to upgrade a carb would cost about the same as getting a header...i suppose higher CFM would be a good place to start and just use less exhaust pipe or less restrictive stuff anyways. i dont really know what would be better...a carb will give u more power over a header since the header wont make too much of a difference with a stock system. I think the highest flowing carb for a stock engine is about 300-350 CFM or something like that...not sure...maybe someone else can help
 
I would say to add headers after you are set with carburation, intake, and cam work. Those will yield the best results for the money. The sometimes forgotten cost of headers is possibly getting a new exhaust system like I did. I went from a stock single out to a dual out. The headers were the cheap part of that equation. But even running a stock head with 2V carb, I don't think you'll notice much gain and I think you'll get more going from a 1V to a 2V then changing to headers on a 1V

Slade
 
Howdy Chris and all:

Know that the air/fuel going in is wet and cool. The exhaust going out is hot/dry. Intake is sucked in from vacuum. Exhaust is being blown out from the combustion burn and piston push on the exhaust stroke. All this, theoritically, makes the exhaust system more efficient than the intake. The air/fuel mixture expands rapidly as it burns, pushing the piston down and blowing itself out the opening exhaust valve. The volume of exhaust goes up fast as rpms increase. A stock exhaust may be adequate from idle to 2,500 rpm. After that, back pressure build to the point that it inhibits performance. Header, header pipe, muffler and tailpipe are all part of the exhaust problem. Improving the most restrictive part, usually the muffler, improves the efficiency of the whole system. An improvement here helps performance/efficiency from idle up.

Typical performance intake valve diameter to exhaust valve diameter and port volume is 75%.

I did not answer you question, but this may help you find your own best answer. I don't remember the details of your engine, but in general, a bigger cfm carb will be noticeable. When you improve exhaust you may not notice a performance increase until you tune and/or rejet to take advantage of improved scavenging.

Slade hit the nail on the head. With improved carburation and cam timing, a header system will allow you to move up the rpm/power scale. Remember the air pump analogy of an internal combustion engine. More air in+more air out=more power. If the displacement is fixed, then the critical variable is rpms.

What do you think?

Adios, David
 
I ran some numbers through Engine Analyzer and came up with some interesting numbers.

If I just added a 2V caburetor and left everything else stock, I would see about a 6-8hp increase and about a 5-8lb/ft of torque increase. Like you said Slade, not much. However, if I keep the 1V and add headers, I'm looking at again about a 6-8hp increase BUT about a 10-12lb/ft more of torque. Interesting. Detectable, maybe? Hmmmm....



-Chris
 
Ignore the last post. I pressed the post button right after your reply. ;) :D

I see what your saying. But did I do something wrong when I ran those numbers. I mean, how come I saw a jump in torque just by adding headers?


-Chris

P.S. My exhaust system consists of a 2" dia. exhaust pipe, turbo muffler and 2" dia tailpipe. All this is connected to a stock manifold.
 
im not sure who but someone did dyno test with a completely stock 1v 200 six, the headers cameout to I believe 1 or 2hp increase and about the same, but with the 2v aussie head/cam/2v carb/ and then adding headers it added like 20hp/30torque...
 
From Mike's Ford Six Parts site:

"Dyno test have shown that a completely stock 200ci engine with only the OZ 250-2V head/manifold, a two barrel carb, and headers yielded a forty percent increase in horse power"
 
I'd go with the headers first. I've always considered headers the foundation of any series of engine mods. Put a set of headers on an injected japanese engine (say a Honda for example) and you get a big boost in performance. However, I did this with my falcon and didn't notice the huge power increase I was expecting. That said, the engine ran smoother, cooler, had a longer power band, and my highway cruising speed increased noticeably. When I added the duraspark and advanced the timing a bit things got even better. When I finally put the weber 38 on, it really took off.

What's my point? An engine is a system. Whichever mod you do first will make some difference, but not as much as you expect. It's not until you have both the intake and the exhaust done that you will realize the full benefits of either. Since you are going to have to do both my preference is to start with the header which has broader overall benefits, but that's just a preference.
 
Depends on the carb type, FF. Mr X has estimated my constant-depression side-draughts at 265+ cfm each, and guesses maybe 15% more with a detail. That's 8-900 cfm total. :shock: Or should I say :eek: ?

Regards, Adam.
 
falcon fanatic":1osy5cbp said:
I'd go with the headers first. I've always considered headers the foundation of any series of engine mods. Put a set of headers on an injected japanese engine (say a Honda for example) and you get a big boost in performance. However, I did this with my falcon and didn't notice the huge power increase I was expecting. That said, the engine ran smoother, cooler, had a longer power band, and my highway cruising speed increased noticeably. When I added the duraspark and advanced the timing a bit things got even better. When I finally put the weber 38 on, it really took off

You are talking about 2 different types of systems. The advantage of the injected engines is they have an ECU that can really take advantage of headers. By increasing the flow, the ECU can now increase injector timing. Like CZLN said, you won't notice the difference of headers until you retune and rejet to take advantage of them.

Think of it this way. You can have a huge exhaust system, but if you have the intake a size of the straw, it will do you no good (like so many import tuners love to do). To take full advantage of the headers, you really have to have the intake ability to see max performance. Which will gain more? Without side by side dynos...we'll never know.

Headers always loook cool though, especially long tube headers on a 6.

Slade
 
I've started in different places (intake and exhaust) on different 200 sixes, and I found the headers to be the more noticeable difference, and it was ALL about the torque. I know a lot of guys on here say just run the larger OEM exhaust manifold with a good flowing muffler and it's not much different than headers, but I personally have not found that to be true. Based on the difference I've felt (and admittedly have never measured on a dyno) I believe the OEM exhaust manifold is a horrible flowing unit.

When I've started on the intake side, I did gain upper end RPM/horsepower, but no noticeable torque.

Since I feel the torque every time I start from a stop, but only feel the upper RPM power when I rev it over 4000, I find the headers to be the way to start. Besides, my mileage has always gone up slightly with headers, never done anything better than stay even with more intake/carburetion.

Just one guy's experience...
 
does the adaptor for converting the single to double barrel carb actually give any noticable gains? or is it just all in the magination..if its getting sucked through the same size hole than does it actually do anything other than dump in more fuel?
 
Howdy Chris and all:

This thread brings to mind Principle #3 of the Porker Principle. The Porker Principle is a set of principles for rotund people to live by. It's is for anyone who has ever been on a diet; for anyone who has lost 25 pounds- the same 5 pounds five times. Principle #3 says, "When given a choice between a fattening food item and a non-fattening food item a Porker will eat both!" Same here Chris. The header and exhaust will provide a great foundation for whatever comes, but the order is up to you and your budget. Ultimately you will want, and need, both.

Dave- It's the size of the hole in the venturi of the carb that is the limiting factor in a stock, OEM engine. An upgrade to a larger carb would be noticeable even through an adapter. For max performance, the funnel function of the adapter would be a limitation.

Adios, David
 
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