Well that's a scarry thought! However if I keep eating like I am I'll make a good Ollie. But then, my personallity is more like Chico.
So, how do like it in these United Snakes? You two are ready for primetime...along w/Evel, Wingnutz, Plowboy, HRP... Help me out here Bros!
Ya just gotta love family: Say the majic woid and win a cigar. Chico, Harpo, Groucho and Zeppo Snakes did someone say snakes?
That is Zeppo's other name. When I was little I thought his name was Zippo and told my dad that his friend a had a Groucho marks cigarette lighter. The Ol' Man kept telling me that Groucho didn't smoke cigarettes. When I was an adult he got me a Zippo for Christmas one year and I said, "hey a Groucho Marks lighter," then he figured it out.
hotroddon is right small long tubes an 3" collector Doug headers are good easy to install. comp headers get more complicated and costly and harder to install. did some dyno test on a 350ct crate with headers recommended by GM and a set of 1 5/8" long tube with a 3" collector which made more hp and torque up until 6000rpm flatter curve
Most everyone making serious power " nowadays" is running a tri-y setup. Long tubes with THREE 2-1 collectors on a side towards the end. According to the dynos that I've seen, they produce an increase in average HP and Torque, presenting a much higher and broader curve. The peak might be less but the average is higher.
I'll briefly touch on some facts to respresent here just how much science actually goes into designing a header. These are just some " food for thought " scientifics for those interested. The I.D. or cross section of the primary tubes determines what's called the " mean flow velocity ", this is a function of RPM and cylinder displacement. Changing the length of this primary tube has a great effect on torque above or torque below the torque peak. Keep in mind, when fabbing your own exhaust system you are trying in effect to create a " optimum pressure balance " between the intake and the exhaust tracts. Through " tuning " the Pipes I.D. and length, we find this balance. A simple matter of too large of a diameter primary tube, and you reduce the " velocity " of the exhaust gases. Reducing " back pressure " is important for high RPM power, but at the expense of killing low end torque. So in a nut shell, the key is too " balance " back pressure and velocity for the RPM range you will be optimizing the engines power to be at. I haven't even touched on V.E. or volumetric efficiency, valve or cam timing, overlap, reversion and a host of other variables. We could also touch on the " collector ' and stepped headers theory, but that will really take up some HAMB hard drive.
You folks with a caculator can work on this formula I have: If we want to keep our exhaut gas velocity in the 275- 300 ft per second range, and have this happen at the RPM chosen say at the peak shift point, to determine if the pipe I.D. is correct we can use this formula: piston speed { over } 60 TIMES bore{2} {over} pipe I.D.{2}. Not for the faint of heart, all the best, TR
31 you can change the torque curve with a try-y setup by changing the primary length, the most important pipes in a try-y are the primaries. Also with the tie firing order of an SBC (and similiar fireing orders) you want to tie #3 with #7 and #1 with #5. On the even side you pair #2 and #4 and #6 and #8. trad I am not getting the entir equation it is: piston speed/(bore(60))(2) ________________________ pipe ID(2) Correct?
the try y gives the best (if built right) broad band power, and the true 180 even more so. but hay going to BI or GC or even TED 3 to 10 times a YEAR might not be worth the HP gain during those times. or even all the money to get it. now race car race, car headers might not be worth talking about in this application. hotroddon has a handle on good info here today... +1 our so cal guy gets the win today... small tip having larger headers than the port will impede exhaust backflow.
The header length application that I posted a link to above, came from Hedders by Ed. If you really want to get confused, look at the headers on a newer serious racecar. A friend of mine races an old Jim Stevens prostocker in Top Sportsman. I was shocked at how small the merged collector was in the venturi area (I don't know what else to call it).
Now I just went from a set of Sanderson shortys to a set of Patriot Tri Ys, 64-68 Mustang , Boy what a difference!!!!! Sandersons were about 450 bucks - Patriots were 178 bucks This was on my roadster, I'll never use a set of shortys again.
Shorties are great for solving fitment issues and aesthetics of nasty manifolds. I think manifolds perform about the same as shorties
Benno, here lets see if a 2" I.D. primary pipe would be good for this engine your building. The engine you are building is a 302 SBC, that will be geared to go through the traps at 7200 RPM and shift at 7000 RPM based on the Power Peak. The engine is a 4" bore and 3" stroke. First we need " piston speed ". So stroke in inches times RPM and divide by 6. 3 X 7000 = 21,000 divide by 6 = 3500. Next is bore of 4" squared or 16. this will be over the following: 60 which is a " constant ". and now Pipe I.D. squared = 4. 3500 X 16 = 56,000 60 X 4 = 240. 56,000 divided by 240 = 233.3333333 ft/sec. This fiqure will be our " exhaust gas velocity " . This shows now that the 2" ID pipe is too large for this engine, as we want ultimately the " gas velocity " to be in the 275-300 ft/sec range. This buddy is only 1 of many formulas that apply to this scenario, TR
To my old friend benno and anyone else playing along, please take note: If you change the primary pipe ID to 1 5/8, you will see that with my formula, the exhaust gas velocity becomes well over 350 ft per second- this pipe is way too small. Change the formula again to a 1 3/4 ID pipe and the gas speed is almost a perfect 300 ft/sec. I don't think anyone would argue that this formula produces results and would also agree on the 1 3/4" primary pipe I.D. to be correct for this engine. I hope everyone enjoyed the lesson, all the best to my friends on the HAMB, TR
quick comment on the shortys, i read somewhere ( i believe it was a thread on here ) that some shortys actually rob more power than running rams horns. i find this hard to believe. anyone else ?
GG people who know a lot more than me have said Dyno runs have proven that shorty headers are just a touch above stock exhaust.
back before everybody had a computer on their desk, secondary tube length was "tuned" by painting them with white paint. where the paint stopped burning off was where you cut and installed the collector.
Shorty headers are no more than sheet metal manifolds and some times because that are not a log and the length is so short that you get exhaust reversion inot the othert tubes, basically the exhaust travels back up the tube to the other open combustion chamber keeping the exhaust from traveling down the pipe and contaminating the following intake charge. Traditions formula works real well, for tube diameter. But needs to be usied in conjunction with a formula to calculate tube length for a given size and RPM peak. Something that a lot of people don't understand and is obvious but the headers that we have seen built on here is that clocking the primaries is as important as length and diameter. one of the things that hurts on a lot of shorty headers for instance is that the tubes are not properly colcked in the collector. You use the exhaust from one cylinder to help scavange the other so you want the tube next to the cylinder that is is scavanging. that is part of the reason that 180 degree headers properly built will out perform standard 4 into one headers. Ideally you want the tube scavanging the next cylinder to be 180 out.
Benno, I have formulas for EVERY reasonable aspect of design you could ever want. Headers, Intakes, Ports, Quench{ your favorite}, Turbo, Blower, you name it, I don't want to get into trouble here as formulas aren't really traditional. I probably have 40 formulas just for header design. I respect that of course and also enjoy sharing the " seat of the pants " testing as much as the next guy. I'm very cool with time slips, and flag drop starts/stop watches, or what have you as these methods were done in the day to prove or disprove performance gains from modifications we made to our jalopy's. I enjoyed getting some cob webs out of my brain for a hour yesterday, hope you had some fun with it too bud, Trad.
treb, this method is still used today as a way to determine the correct placement for a dual exhaust " crossover " point, such as a X pipe or a H pipe crossover, works pretty well too sir.
I apologize to anyone having trouble with the formula. I am a engine builder and not real good with the computer and I'm having trouble " writing " the formula w/ the fractions and equations on the computer. I gave some examples to show that it indeed works and possibly to help undestand what I am unable to correctly write out.
Here benno, I did one with a 4 1/4" stroked Harley engine for you ol' buddy. Bore= 3.500" Stroke= 4.250" Pipe ID = 2" RPM= 5600 Piston speed= 3967 Results= 202 ft/sec exhaust gas velocity= 2" primary header pipe too large for this combo! It doesn't matter 2 or 8 cylinders, oversqaure or undersquare engine bore/stroke doesn't matter.
Put it down chalkboard style and take a picture of it. What are you useing for piston speed ? Calculated average ? Its quite different all along its stroke.
When everyone thought that you had to have 2" pipes on their harley I was running 1.875 x 40" pipes on my 101. Came after a long discussion with a very close friend and engine builder, he said just try both sets and tell me what you think, the smaller pipes produced an extra 3 on three dyno. Go figure.
I concur with your results 100%. You lose way too much " velocity " with the large pipes, no different than velocity lost with excessive porting. Harley's present a mul***ude of their own unique issues due to the firing order, and the common crank pin and are extremely sensitive to pipe diameters and length's and collector diameter/length when used. The intake track is another designers nightmare all together. Again being very sensitive to intake runner length/diameter, even air horn length. Always remember the two key V's to engine building, componant design, and acheiving peak volumetric effieciency: V = Volume V = Velocity
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