anyone have a link on the performance diff. between shorty headers and long tube headers. i read a lot of talk about them but no testing readings. a dyno chart of the two would be nice. ...frank...
Frank, There isn't always a huge horsepower difference. Long tubes move the powerband up allowing the motor to make it's peak HP at the appropiate RPM. If you are putting headers on the "Frankensteiner" Go shorty. Your car is set up with an RV cam and isn't gonna spin to the point of needing Long Tube headers. I have seen actual dynos showingthe difference. It all just depends on the motor set up.....
thanks Buddy, Note how this shorty header minimizes the collector length. Generally, this is done to make it easy to fit the headers in the chassis. This mini-collector generally costs low-speed torque. If you have room to extend the collector length by 8 to 10 inches, this could improve torque.
You got it backwards. Shorter tubes, just like shorter collectors, move the power band UP. Longer tubes create lower rpm power. The idea behind using shortys on the street is SOLEY for fit. They are better than manifolds and they have good ground clearance. They are a compromise. If you don't have ground clearance issues, LTs are always best. Dave
The graph you have here is a little misleading. The top (A) is about pipe diameter, not length. If you use same diameter pipe, long tubes make low rpm torque, short tubes make high rpm power. The lower (B) appears to show pipe length comparisons, but is a little vague. It appears that the blue line is a baseline tube length, and the red line shows what happens if you shorten the pipe, while the green is lengthening. To read it like that is the only way that makes sense. Dave
http://www.carcraft.com/techarticles/header_basics/ Okay, I found the text for that graph. The link is at the top, and the text pertaining to the graph is in quote. The entire article is in the link and seems to be good reading from the few paragraphs I read. Dave
Dave, I am refering to the Horse power. A basic rule on collectors is that shorter, larger diameters favor top end while longer, smaller longer diameters favor the low end. Horsepower vs torque. In Franks case he doesn't have the RPM capailities to use the Long tubes. He does have lotsa torque and matching parts is one of the best things for any combo. Concerning primaries Big pipes flow more, so is bigger better? Answer: absolutely not. Primary pipes that are too big defeat our quest for the all-important velocity-enhanced scavenging effect. Without knowledge to the contrary, the biggest fear is that the selected tube diameters could be too small, thereby constricting flow and dropping power. Sure, if they are way under what is needed, lack of flow will cause power to suffer. In practice though it is better, especially for a street-driven machine, to have pipes a little too small rather than a little too big. If the pipes are too large a fair chunk of torque can be lost without actually gaining much in the way of top-end power.
I don't know if we are talking about 2 different things or what. Your post refered to "tube length". The baseline of the engine's peak power is regulated by the diameter of the primary pipes. Larger diameter will place the peak higher than smaller diameter. On a 350 engine, 1.625" tubes peak about 4100 rpm, 1.75" at around 4600, and 1.875" around 5100. Now the primary length determines how much of the power band is going to be above and/or below the peak. It does not change the peak, just shifts the best power around that peak. 1.625" tubes will peak torque at 4100 rpm. If they are short, the power band will be peaky up to 4100 rpm, then flatten out. If they are long primary pipes, the power will be flat to 4100 rpm, the fall off drastically. Now comes collector tuning. Longer collectors will add torque to a point, between 2500 and 5500, HOWEVER, unlike primary pipe changes, they will NOT decrease power in high rpms. Going by this, and Frank's RV cam, he should be looking at 1.5" to 1.625" primary long tubes with collector extentions. IMO 6901s with some extentions and H-pipe. Shortys will work, but will not provide the lower rpm torque of LTs with the same primary diameter. Not to mention the short collectors. Dave
Oh no dude, you're totally wrong. Bigger is better.....with everything. Don't you know that??...:evilsmile
I noticed a slight drop just above idle with longtubes over manifolds, but the power increase over the entire range up to valve float was great. I've never run shorties, so I can't add much, but the longtubes were not a hinderence to low end power, the size of the primaries vs the restriction of the manifold probably caused my slight loss from 800-1200 RPM. I can tell you this, bolting long tubes on a 92 GT showed improvement at all RPM over the factory shorties. Probably a good 20lbs of torque increase all the way across the board.
Here is a thread from another site that shows the opinion on this from a somewhat "knowledgeable" person ...note his signature credentials. http://www.mustangsandmore.com/ubb/Forum12/HTML/011417.html
Shorties are much better than manifolds, longtubes are better without a doubt. I don't think the difference between good shorties and longtubes is near the difference of manifolds to shorties.
The differences in long to short are intresting. Glad someone pointed some things out (ratio). As for the other stuff...
