Headers

I see a few questions posted about headers.

For those of you who are allowed to run them, are your RPM's limeted to a certain amount or percentage over stock?

I've built several headers and helped on several more. I've had people tell me that there is no way a header will help. But that's not the truth. A well designed and built header is one of the most important (possiably the most important) components of a performance minded build. A poor header isn't much if any better than a stock manifold. And those nice sets of "zoomies" or individual pipes are the worst, great for a blown application but terrable for naturally aspirated.

On my own tractor I had used a friends header, I was waiting on parts for mine to arrive and time to build it so I simply put his shorty header on the engine for the time being. It worked alright and when the parts arrived and time allowed we built a tuned length, equill length runners with a good paralell merge collector in rotational fireing order. Did a lot of figureing on tube diameter, length and collector sizeing. I gained 25% hp and 1200 RPM on top speed with a "good exhaust header", not changeing anything else other than tuneing adjustments. There's likely more to gain, but one can only try to fine tune something to a point but then the real work has to get done and the fun projects have to sit. The first time out with the new header we tried it in the normal gear for the class and then came back and shifted up a gear and the engine still lit hard and went for a win.

here's a couple forumulas for intake length you gear heads,

L=(90XV) divide by N
N= engine speed in RPM, V = speed of sound, L= length


another simple one is

length=93,500 divide by engine RPM


a couple simple ones for exhaust length

L=205,000 divide by N where N = RPM and L = length

or

Lft=(135XS) dived by N where N=RPM, Lft = length in feed, S= number of crank degrees from exhaust valve opening to intake valve opening

In all instances length is tuned to the middle of the desired power band. As an example Iknew I had enough airflow to support a certain sized shortblock at a certain speed for peak torque, tuned my intake and exhaust for 4500 RPM, the engine was planned to top out at 6000, and make it's power from 3500-5500 RPM. It ended up topping out at 6500 RPM with light load, but makeing good power from 3500-5500 RPM, and below 3000 it falls off fast, above 5500 it came down fast.

Thanks for all the information! Do you have any formulas for the intake? Thanks!

there's two simple ones above for each intake and exhaust.


I'll try to post several more, some use camshaft specs, and some get pretty involved. Some for tube diameter, some for length, some for collector length. If you wish I could easily copy a few pages and send you.

None of these are right, none are wrong. There's many different ways to get an end result. It's alright to use a few different ones and take an average.

Yeah that would be great! My e-mail is: [email protected] Thanks!