Loop Engine Exhaust Systems - An Analysis
There have been several questions regarding the exhaust configuration implemented on the Quincy Welding (QW) Flathead (Loop) Engines. The siamese exhaust system, in which two exhaust ports per cylinder converge on each side into a common exhaust header pipe, was unique--at least in that time period (1964 - 1973).
Of particular interest is the effect of this port arrangement on the attached exhaust system; that is, the header pipe and megaphones or expansion chambers. Also of interest is the exhaust divider, the design of expansion chambers, and the wave action in the various systems tested. Water injection is also a favorite topic of discussion. Unless you live in Canada, then it's a favourite topic of discussion. :)
This post is a placeholder to hopefully field these questions in a central location, and may be edited from time to time to provide upfront content info or a general framework for the discussion.
Frank
Getting Back To What If The Flatheads Went To A Single Exhaust Port?
Ever time I look at a Quincy Flathead block, the amount of and the configuration of the ports of that engine back when they first came out must have blown the cans off everyone in terms of here we go! If those were the first halting steps of Loopers / Flatheads and they were it was like starting at the gate with a JATO rocket welded to hydro. It seemed like there was no slow revolution / evolution inside those blocks to think of and who knew what about expansion chambers at that time anywhere? It was pretty much nill.
The blowdown Smitty is referring to? Is the speed at which the engine released the expanding detonation of air/fuel as it approached the exhaust port on that part of the cranks spin? If so the idea was to get the exhaust out of there with such a wave gone from positive to even negative to help suck the next incoming air/fuel charge into the cylinder on the heels of the exhaust wave zapping out the pipe helping pull that new air/fuel charge so as to have a crankcase side pushing and the exhaust pulling making it the cleanest charge possible for the next detonation. Back then, it was conventional racing exhaust wisdom put in a Loop engine.
Its only since the advent of bounce/expansion/stinger pipes have we seen that the Quincy engine would adapt to yet another system not belled. It was only in more recent times with computers and software(s) where it has become clear that the Quincvy Flathead would indeed have benefitted from going to a single exhaust of given area to a single exhaust spec'd made with todays software that many believe seeing it that the Flathead design was not as dated thought. If the engine had changed to that single exhaust port and fed only one pipe, it would not have changed the way the engine looked, sounded yes! But, the performance would be also increased by what some are thinking could be within the 20%+ range in doing so.
I would love to get a Quincy C Flathead block, do the math, change the exhaust to single exhaust port liners and hang a todays modern day expansion chambers from her. I don't think there would be any surprises except to those who said a single exhaust port and expansion chamber exhausts would not go over and only because they said that decades ago.
Things and thinking sure do change but only changed with the times. You guys at Quincy were marvelous and way ahead of your times in your time! :)