I searched here and elsewhere... found loads of examples, but haven't really found the 'why'? Just for the sound? Or is there some sort of performance theory?
I split the manifold on my flathead Plymouth I/6 and added dual exhaust. It seems to increase the power band and the little engines need all the help they can get. I also have dual carbs and a mild cam and milled the head .100 which also helps.
Mainly for that rapping sound but it also helps the engine breath better so you get a little more pep.
Have you ever heard the sound of a split manifold on an old six? A sweeter noise you will never experience.
To better control exhaust manifold pulses. My Dad's 1967 Pontiac LeMans Sprint with the OHC-6 4 bbl had splits, sure sounded good:
Well, why not? If it's good enough for the first Vettes it's should be good enough for Dads old sedan! Besides, like it's been said, they sound cool. Dom
That's the same question my dad asked me when I was in HS and I wanted to put duals on my '49 Fleetline. I told him it made the engine run cooler, last longer, and get better mileage. He then loaned me the $30 to get a split manifold from Sears and Roebuck (yes, they used to carry lots of hot rod stuff) Real reason = you can't beat the sound of an inliner with duals. That was 50 years ago, I still run Fentons and 22" Smittys on my 235. Still love that sound!!!
so - everyone has a traditional 3-3 split front to back? i understand the performance gain from that. BUT - i have always thought that the 'rappy' split exhaust was a 2-4 split, which i'm not ever sure what it is (other than 2 out one, 4 out the other) - which seems like it would have some sort of bizarre pulse stream. so what split is it that makes the sweet sound? if it's the 3-3 split, then what is a 2-4 split? oh - and why?
I think what your talking about is the way the cylinders are split into the exhaust manifold? The 2 4 split would be the fact that the first cylinder is exhausting out on it's own and the second and third cylinders are sharing the second pipe of the manifold. Three and four share a pipe with the last cylinder on it's own. Right? The six exhaust valves are split up amongst four outlets in the head. Dom
There is no "2-4" split. A stock exhaust manifold has a common plenum. When it's "split", there's simply another opening for the exhaust to exit. The only time the exhaust is actually split, is when an after-market set of dual manifolds is installed. I honestly can't say that I've heard a six with a modified stock manifold, and knew it. I have heard dual manifolds, and I'll tell you, they rap. Maybe you can find a running car on youtube with the modified stock manifold, and compare it to a video of a car with dual manifolds.
I allways used the 2-4 split, I never had to do anything to the heat source under the carb. by staying away from it . The why is , because I can . I liked the sound to.
Wrong. A stock straight six exhaust manifold has a common plenum IN STOCK FORM. A very important part of splitting it is to, once the second outlet has been added, internally divide the manifold into two separate chambers so that three cylinders dump into the stock outlet and the other three dump into the new outlet. Simply adding a second outlet doesn't make any additional sound at all. A friend added a second outlet to his '54 Chevy truck without dividing the manifold and, even with dual glasspacks, it was still whisper quiet. I cut open the back of the manifold and inserted a steel divider plate-----BIG difference in decibel level! The "2-4" split was usually done on manifolds that were difficult or impossible to split evenly; the Ford 223 comes to mind, since its center two exhaust ports both dumped into the stock outlet below the heat riser.
I stand corrected, HEATHEN. I wasn't aware that a separator plate was traditionally involved. So without the plate, it is a common plenum, but with the plate, it's a 3-3 split...correct? So there is, in fact, no 4-2 split on the Chey. I like this place. 100,000 heads is better than one.
Right. Because of the 216/235/261's 1-2-2-1 exhaust port arrangement, it's ideal for an even 3-3 split.
153624 usual firing order .on our old stockcar we made a header flange ,153 ran to a cone and back via 3 feet of 2inch pipi 624 did likewise . sure sounded cool but pulled a tad harder out of the bends when the two 2inch collectors were joined at about half their length and had half what was left welded on . didnt sound as evil but we left it as this .Blueflame six ,destroked to 221 ,600 4bbl dirt track in New Zealand .
I ran cylinders 1-2-3 into one collector, and 4-5-6 into another collector. What you end up with is equally spaced exhaust pulses in each individual collector 240* apart that are easily tuneable by the length of the collector. The open headers at RPM have the sound of a radial airplane engine. The reason V-8 collectors sound rough have to do with the uneven firing pulses emitted from each collector.
I split my flathead six with tube headers and a crossover just ahead of a pair of smithys. No rapping or rackackack cackling, just smooth music to my ears...
When I had them split we cut the manifold in to two seperate parts . Capping each one off , then making a outlet for the short one that came off of two cylinders. We were not concerned about a good flow of exhaust , just lots of noise . This was back in the 1950s
<object width="425" height="344"><param name="movie" value="http://www.youtube.com/v/smyHCN2DNC8&hl=en_US&fs=1&"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/smyHCN2DNC8&hl=en_US&fs=1&" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="425" height="344"></embed></object> This is why
but, on a chevy 216 or 235, the exhaust ports are set up as 1 - 2 - 2 - 1... not sure that could be cut the way you are describing it. it must have been something set up like 1 - 1- 2 - 1 - 1? ford?
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