5.0 mag: BBK longtubes make LESS power than shorties

I've gotta throw the BS flag on this one. Sounds like a pay off or a fluke. It's a proven science that LTs make more power or people wouldnt have been using them for the last 40 years in racing. One dyno run by 5.0 means nothing in comparrison.

Hey guys... the long tubes are better for power!! and IF the mag did a bolt on and run, there is a good chance the long tubes DID make less HP!! With the lean running 5.0 and increase the exhaust flow and engine scaveging the engine WILL loose power and run SLOWER!! When I did my first set of headers, I ran to the track expecting POWER FROM hell!! ahhh the sound, the power, the low end!! Duh... went .3 SLOWER!! But after tuning the carb and ign timing, I made up that lost .3 and knocked another .5 off!! We all know there is no such thing as Bolt on and go!! Huh??!! You have to really READ those articles, and see if you can see the whole story!! Like the 20 HP from those Valve springs... Hell any valve spring that would stop the valve bounce would have corrected the problem... but I'll bet a lot of readers of that article think those Valve springs are a 20 HP Bolt on!! LOL

Just me.........................

Thumper

ive always been under the impression long tubes dont neccecarily equal more hp
but they do equal GOBS OF TORQUE.

GroverDill said:

peak numbers are not everything, what did the curves look like?

its all about the area under the curve.

Click to expand...

Exactly. The LT's should have more area uner the curve.

On the subject of BBK LTs, what is the size of the collectors on one?

You will usually make more horsepower with shorty's BUT you will make more TORQUE wuth LT's.

If you have a mostly stock engine accept for simple bolt-ons you wont see the bennefit of LT's. The only way you will see big gains if you get the fuel curve remaped or you have a power adder. A mostly stock N/A car simple isnt flowing that much air unless its properly tuned. Otherwise there is no sense getting away from shorties. Which I'm gonna go back to or switch to BBK LT's....havent decided yet.

Long tube headers work just like the tuned runners on the intake manifold. The column of hot gas has a resonant frequency just like the intake does. However, it is a lower frequency and takes more length to get it into the resonant range. Measure the tube length from the valve to the point that the individual tubes come together at the collector and that is the resonant length. One of the engineering types should be able to come up with the formula to determine the perfect length for the 3000-4000 RPM range that matches the intake tuning of most Mustangs. Tune both intake manifold and long tube headers to the same RPM range and you'll get a real spike upwards in the torque curve. Offset the RPM range so that one tunes just slightly after the other starts to fall off and you'll get a broad, smooth torque curve.

I had LT's but had to take them off for the smog nazzi's. After putting my shorties back on and having the system tuned for best flow and velocity, I think i'm just going to stay with them. My BP is extremely low with the shorties & it's plenty loud. I can't justify the hassle involved, the collector's scraping over speed bumps etc etc plus cost of welding everything up every 2 years for just a few extra HP & TQ. The N20 more than makes up for that.

Ed C has run 1 5/8 headers on some VERY quick cars. Like what was said, it's all about the area under the curve.

Here's a Quote from Ed with regards to internet myths.......

How about another Internet gem?

"You need 1-3/4 tube headers on a 306 to make big horsepower...."

I work with two extremely fast NMRA Pure Street racers that run 1-5/8 headers on their 400+ rwhp cars.... Guess we're doing something wrong!

Ed

Oh and it seems like I'm always under the torquing the bolts at the header to h-pipe flanges...never had a problem with the shorties vibrating lose.

with my o/r x-pipe - will the computer tune the engine enough to take advantage of the improved exhaust flow - or do I need a diablo chip installed to do that?

your computer should relearn somewhat in a few days to the changes, just give it a chance and a few wot learning experiances for it. after my exhaust it took several days before it truly came to life.

The reason why the long tubes made less power is because of the size of the collector. BBK uses factory type ball joint collectors. It deosn't matter how big the tubes are, if you can't get through the collectors you can't make power. My friend just got BBK 1 5/8" LT's put on his 331. It made the same power as the shorties that he had on which were FRPP 1 5/8. Since he couldn't return them he decided to cut off the collectors and put on race type 3 bolt collectors. He picked up 15 hp and 12 ft. lbs. of torque. Now his power is at 405 RWHP and 393 ft. lbs.

Is this the artical that put Hooker headers with weld on flanges on and picked up 15 hp over any of the BBK? I thought I read this magazine artical? What issue is this?

ball and socket LT's are not an optimal setup.
BBK LT's are neither 'tuned' nor true equal length.

Thumpers gains at the track of 0.5 are most impressive.
Likely carb'd cars need more user input than EFI cars.
Long tubes netted me 15+hp(forget actual number) but at the track I gained 0.3seconds.
Clearly, the peak number tells only a portion of the story, as my average power/tq must have been way up.

Wow, fiery topic. I just have to interject, too. I have some experience there, and all I can say, is that my current setup makes butloads more low and mid range power, and I think that the LT's are no small part to that. And even if the did make more peak power with that engine with shorties, it doesn't really matter, since ever engine will respond to different setups differently. Just because AFR 185's make 530 horse on a Ford Racing 392 crate motor, doesn't mean they'll do the same on a stock 5.0. Like I said, every engine is different. But I do say long tubes a coolio!!

89sleeper he welded on a biger collector on his bbks and made more power? hmm i have the bbk long tubes and may be that would be a fun project after my new motor goes in. do you have any more info on what he did?

Thumper460 hit the nail on the head about 10 replies ago. If the mag was just bolting on headers and making pulls, that's not even a comparison. Shortys do not make more horsepower than longtubes. I had alot of tuning to do when I went from BBK Longtubes to my Bassanis. They all scavenge different which has a direct effect on how much fuel the engine wants.

jrichker said:

The column of hot gas has a resonant frequency just like the intake does....... One of the engineering types should be able to come up with the formula to determine the perfect length for the 3000-4000 RPM range that matches the intake tuning of most Mustangs.

Click to expand...

Some interesting reading on the subject..............

Drone in the exhaust is due to the engine driving the exhaust system
at its resonant frequency. You can't get rid of it, any length of pipe has
a natural frequency, but you can change the frequency (RPM) it happens at.
Stock exhaust systems are tuned to put the resonant frequencies outside the
normal RPM range the engine is run in. Sometimes they add resonators for
this purpose. To raise the resonant frequency of a system, shorten its
length. To do this, you can try tail pipes that exit by the wheel (like
GN's have), or you can try a muffler with a shorter internal flow path. If
you have a true dual system, you can change the natural frequency of the
system dramatically by adding a balance tube. If you can't shorten the
system, then you can add slightly less than one wavelength of pipe. This
will also raise the resonant frequency of the system. The wavelength in a
single converter system (not true dual) is a little less than three feet at
3000 RPM. Shortening the system by a foot or so will move a resonance at
2000 RPM to about 3000 RPM.

To move a resonance, calculate the wavelength at the RPM that gives
the resonance you want to move. Then calculate the wavelength at the RPM
you would rather it be at. The difference is the length of pipe you need to
add or delete. Add to lower the RPM, delete to raise it. If you want to
raise it but you can't cut any pipe out, then add one wavelength of pipe
minus the amount you calculated. This will have the same affect. If you
add or subtract a multiple of a wavelength exactly, you will not change the
resonant RPM.


Wavelength = 1100 X 60 X 1/RPM X 1/4 X 1/2

or

Wavelength = 8250 / RPM (=16,500 / RPM for dual system)

Wavelength = standing wavelength
1100 = speed of sound in air in feet per second
60 = convert RPM to Revs per second
RPM = RPM
1/4 = four cylinder firings per revolution (make this 1/2 for "true dual")
1/2 = standing wavelength is half the wavelength of a "normal" wave

yea, what tmoss said