Technical > Matt Shaff's Engine Shop
Zoomies vs collector headers
wideopen231:
If anythinhg I hope that 5500 to 6500 is only place you loose.My combo is setup to leave at 6800 and shift at 7600 and cross finishline around 8800 to 9000.I can see zoomies loosing out on bottomend and have no problem with that.
noslin:
--- Quote from: Roger on February 14, 2017, 06:56:39 AM ---
After talking with 4 different cam companies (who all had a little different idea of what was needed) they all pointed to a cam that needed more exhaust duration, an increased lobe separation angle, and minimum overlap as compared to a similar cam used with headers. Jones Cam Designs told me they did some tests years ago using zoomies and were emphatic that the exhaust side of the cam needed 10 degrees more duration than the intake.
--- End quote ---
one thing ive learned from hangin with my buddy who is the gearhead when it comes to engines. he is a n20 guy, from what i understand the n20 guys move the exhaust lobe depending on how much hp they plan on making. i think technically, they add the duration for the added exhaust from the n20 but then have to move the lobe to get the overlap back where they want it. so, maybe in the sense of what the cam gurus are trying to do is help the scavenging of the exhaust by haning it open longer and also as the n20 cam guys do, move the lobe to get the overlap where it needs to be. i dont know if this is correct thinking but its something to discuss.
i wonder if its really fair test if just changing the headers and not changing the cam. if setup is designed for collector style header setup and put zoomies on or visa versa, is it really an accurate assessment if one makes less/more hp then the other.
dreracecar:
Exactly, If only we could build our motors from the Jegs or Summit catalog based on advertised HP gains listed with the parts, one could build a single carb 350 Chevy that made 1200 HP for $2500
noslin:
--- Quote from: dreracecar on February 17, 2017, 08:08:11 AM ---Exactly, If only we could build our motors from the Jegs or Summit catalog based on advertised HP gains listed with the parts, one could build a single carb 350 Chevy that made 1200 HP for $2500
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you sure your on the right thread?
Roger:
My view of how to maximize power output with zoomies falls in line with what wideopen231 & noslin have said. If Stahl’s concept that you lose power between 5500-6500rpm is correct, then have a convertor that flash stalls to at least 6,000rpm to minimize the hole in the power curve might be a wise move just as wideopen231 mentioned.
As far as noslin’s thoughts, they might be right on the money. If you don’t have the effect of a collector headers to help evacuate the cylinder then you have to do something like opening the exhaust valve longer to do a better job of clearing the cylinder of burned gases. And to keep exhaust reversion, that’s exhaust flowing into the intake, to a minimum then add a few degrees of lobe separation in order to reduce the amount of overlap time for the reversion to occur. That’s the way it was explained to me by some very experienced (didn’t want to call them old!) and well known cam designers. Of course, this has little if anything to do with supercharged engines. But they weren’t the focus of my original question, I probably should have made that more clear.
As far as changing a cam and headers, the best I can do is use the same cam designed for zoomies with more exhaust duration and a wider lobe center angle and then put the headers on and see what happens. But it’s a good point.
Picked my updated car up from the chassis shop today so here’s a quick photo. Will post more in the Altered section after I get back from a short leave.
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