Question brought up by "Better size header"
 

In reading the thread on "Better size header" the concensus was that for a mostly stock engine, 1 5/8 were too big.

My question is this. Will my car benifit for bbk 1 5/8 longtubes?
On my 92 gt, what I have right now is cats cut out, black magic electric fan, underdrive pulleys, and a k&n box filter.

During spring break, I have to install an explorer upper and lower intake, a 65mm throttle body and 67mm egr spacer, and the ceramic 1 5/8 bbk longtubes with matching h-pipe.

I am saving up for 96 explorer heads and dynomax ultra flo weld mufflers.

I am pretty sure that the car will wake up when I get the gt 40 heads, but will I lose anything with the headers and the things I am going to do during spring break?

???anyone???

1 5/8 headers too big??? Think of it this way,try breathing thru a small straw underwater,then go to a larger size,which one has less restriction?,exhaust gasses need to FLOW,backpressure of any kind makes your engine work harder to rid itself of them,I run Hooker super comps on mine and gained a TON from the upgrade,keep the long tubes on and breath easier.

"Think of it this way,try breathing thru a small straw underwater,then go to a larger size,which one has less restriction?"
That doesnt make sense to me. Your trying to compare apples to oranges. If say for instance your mouth is 1 1/2" in diameter why would you compare a straw to a 1 1/2 header? To use your comparison you would start out with a 1 1/2" straw. If the ports on a 5.0 head were say 4" large I could understand your logic? But they are not.
And backpressure plays a big part in an efficient engine "velocity" . Why do you think tech articles report a loss in torque with a header primary that is too big for the combination?

i agree squid, just going to a larger dia header and large exhaust will not pick up power. its all about the combination. for a car that will stay stock forever then i would say go with the 1 1/2" size but if you have any upgrades in the future planned that are not way to radical, then the 1 5/8" size will be perfect.

basically, you will have a GT40 intake setup and a 65mm tb and 67mm spacer but still have the stock E7 heads until you can get enough money for gt40's.

you may lose a little torque if you put 1 5/8" pipes on with the E7 heads.

so your question is with all the mods above which would be the better longtube pipes: 1 1/2" or 1 5/8" ?

not sure if you would really benefit from 1 5/8" tubes with regular GT40's......anybody got some numbers they could post?

So, should I leave on the stock headers and sell the bbk longtubes? What type of heads would those headers benefit?

I thought longtubes would be better all the way around over stock headers, for low and high end and torque. :confused:

If you already have the longtubes then stick them on. The point I was trying to get across is that you should match your purchases to the combination you are going to have for a decent amount of time. If you put long tubes on an engine with stock type heads your only going to see an increase in horsepower just before the heads give up in rpm. Stock type heads would need some serious porting to utilize the power potential of long tubes. If you know your goint to slap on a set of high flowing heads in the "near" future then you have exactly what you need in long tubes. The factory headers even though they seem very restrictive are not one of the bigger gains in horsepower or torque to replace when your early on in your mods.
If your going to stick with your longtubes then have that explorer intake ported, the gt40 heads really ported especially on the exhaust side , better valve springs,(or get some already done like thumper heads) slap in a custom cam, bigger meter and hang on. I hope some of this helps.

I'm not usally that big a fan of the mags, but if you have noticed recently they have tested a couple of decent combo's that did not gain any power w/ 1 5/8 shorty headers over stock headers. These were not stock combos, one was a complete edlebrock package the other was trick flow intake, anderson cam and powerheads. i think for a long time you didnt see these dyno comparisons w/ the headers because the advertisers had hyped headers up so much that the mags did not want to expose the reality and lose the advertising dollars. Now w/ the 4.6 market expanding and 5.0 market saturated it's different. How many 5.0's could possibly be adding shorty headers now as compared to several years ago. Next up is throttle bodies on milder packages showing little to no gain I'd assume.

Back pressure in any form is a power killer, thats a force the engine has to work against in order to produce power. There are no positive benefits to back pressure what so ever.

That said....

Primary pipe dia. seems to be dependant on the volume of exhaust that the cylinder is capable of expelling during the exhaust cycle.

Here is a formula for determing the needed dia.

(CID / # of cyl) x RPM /Pi x ^2 + (pipe wall thickness x 2) = desired primary pipe O.D

Notice that its all volume related.

You can plug in whatever rpm your looking to work with, be it peak torque, or peak power or whatever. Also note that an engine reaches peak volumetric efficiency at peak torque (100% or better), but this isn't nessecarily the highest volume of gas that then cylinder is trying to expel (anybody with a dyno sim could monkey with this and determine the best possible pipe O.D over the widest range of operating rpm by pluging in the observed VE in the first part of the formula then plug in the rpm where it occurs).

Now onto header length. I haven't the foggiest on how to determine proper primary tube length, however I bet the more accurate formulas use some info from the cam timing events (or not??) since a header design is governed by the same princples used to tune an intake manifold.

Then again primary pipe length could also be tied with pipe diameter as it relates to cylinder volume? (but not in the resonant tuning capacity which is length dependant)

Anywhosit, I assume the formula is tuned (no pun intended) for the proper dia needed to maintain proper gas velocity at the desired RPM.

all i can say is, stick with the stock headers if you are planning on running stock heads or GT40's. i put the 1 5/8" Mac unequal shorties on, and i LOST a considerable amount of low end, but gained it on the upper end around 5200. Useless if you ask me for my somewhat stock motor. Those stock headers are not restrictive at all for what the application is used for. My opinion, Ford did it well with those headers for the application. Trust me i wasted my money. Yeah they look cool, but that is about it. As for long drops on a stock motor(E7's) we are talkling about something different cause of the design.

I have do disagree with you MiracleMax. On a stock or mildy stock motor, you need back pressure. Run straight long drops on a stock motor and i will run my stock headers with aftermarket exhaust on mine. i will produce a better "useable" torque curve than you. Dont ask me for equations, cause i dont have them!:D

Went to the track last night to test the car w/ the headman 15/8 equal's. Surprisingly I ran the same consistent 13.40-50's that i did witht the stock headers. MPH was down about .5 from normal. Car weighed 3160 w/me and 3/4 tank of gas. i honestly thought the car would lose a couple of tenths, because i fealt like I had lost so much on the low end. Probably swap back to stock saturday and go back out to the track sunday to test again. I will post the results.

What kind of heads should I be hunting for to maximize what I have?

What should be ported on the explorer intake?

Should I even bother putting the things I have on next week, or should I wait until I have the heads also?

I guess it depends on how long until you get the heads you want. If I was going to spend as little money as possible I would buy some thumper or powerheads and have your intake ported and slap all of that on together with your long tubes since you already have them. It really comes down to money and time. You say your saving up for heads and mufflers right. What about forgetting the mufflers and pipes unless of course yours are shot, take that money and put it towards your heads. The big restriction is your heads. Not the headers or mufflers.