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I have an exhaust manifold that splits the 1 & 4 cylinders from the 2 & 3 cylinders and thus has 2 outlets from the manifold - It was on the back seat of a '63 544 parts car that I purchased last year. What is that manifold from? Also included in the purchase was a B-20 block with no head so I thought that might have been for that engine. I would like to have a split exhaust and wonder if the 1-3-4-2 firing order lends itself to a split exhaust with the 1&4 in one pipe and 2&3 in the other per the manifold I have - there is a 4 into 2 into 1 exhaust down pipe available and it seems I could cut that before it goes into 1 and run the 2 pipes separately. A friend of mine who is a superb mechanic advised against it because of "the exhaust pulse" is wrong. I'm too slow to understand what he meant - that would be nice to know but mostly would a split dual exhaust, as I described, work and would it make a wonderfully sporty sound and not destroy the performance? I'm not up to speed with including photos in this form but I can email them if anyone wants.

Thanks. Mike
 

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Mike;

I think your mechanic is referring to the sequence and timing between exhaust pulses, as they hit the exhaust manifold and system downstream...ideally, as with headers, the equal length tubing causes them to be equally spaced and sequenced at the collector, so because of this equal length, and hopefully some length and frequency (aka RPM) tuning, this will lead to scavenging at the collector which would serve to help extract exhaust from other cylinders...for the 4 into 1 manifold, flowing through a stock exhaust system, there is so much flow restriction downstream anyway (even if you did have more than an A Cam), that worrying about it here is totally misplaced effort IMO...for the 4-2-1 manifold its a lot better, and the 2-1 pipe combines the flow far downstream of that (also with some scavenging effect), so that is the desirable exhaust manifold, but still nothing to worry too much about if you have a stock exhaust...if you need to wring the absolute most out of an engine, a much hotter cam, a ported head, a header, separate intake manifold, a much freer flowing Exhaust System, and hours on an engine dyne to optimize carbs, and ignition curve, are what you need!...if you are building a good roadcar (with bearable exhaust noise level), use the standard setups and don't let your mechanic friend make you crazy with details which are fun to discuss over a beer, but pretty much irrelevant unless you're on the racetrack...!

See also: http://www.sw-em.com/manifolding_notes.htm

Cheers
 

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One thing I've learned over the years - the fewer cylinders you have going through an exhaust pipe, the louder / harsher the exhaust will sound. Your car will sound better, run better, and be lighter with a 4-2-1 setup with a decent muffler, than with 2 mufflers and two tailpipes.
 
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