Psyko Posted March 31, 2009 Share Posted March 31, 2009 (edited) Well, there isn't much information on the dual carb EA81s around here, so I thought I might share some pictures of the DC cam next to a hydro one. Be warned. Just a few large pictures. Hydro "76" stamp. Very awesome "77" for the DC. Rather astute pupils should see the main difference between them now. Hydro: top - DC: bottom Not totally obvious yet, but pretty easy to see. Hydro: top - DC: bottom Main difference is about as obvious as possible now. Hydro DC When I took the DC cam to Delta Cam to look into a grind, Qman told me the hydro actually was a bit hotter. Easy to see the truth of that, with the pictures. Hydro to the left. The lobe is fatter all the way around. Hydro Bigger lobes. DC Sleeker and, uh, sexier lobes... I guess? :-p Hydro DC So, there you have it. Any other curiosities, let me know. Thanks John! (Not sure why some of them are rotated in Photobucket, but not here.) Edited March 31, 2009 by Psyko Quote Link to comment Share on other sites More sharing options...
Jerry DeMoss Posted March 31, 2009 Share Posted March 31, 2009 Cool pictures. That being said with the hydro cam is why I send the hydro cam blank out to get reground with the solid lifters because there is more material there. I am going to use a hydro cam with solid lifters in my ea81t in a hydro block. Quote Link to comment Share on other sites More sharing options...
subiemech85 Posted March 31, 2009 Share Posted March 31, 2009 obviously lobes are pointed different ways what's the spec of degrees? how does it compare to turbo and single carb? Quote Link to comment Share on other sites More sharing options...
Psyko Posted March 31, 2009 Author Share Posted March 31, 2009 I'm not sure what the different specs of it are yet. When I get the chance I'm going to take them both back down to Delta Cam and see if I can learn a bit more. Quote Link to comment Share on other sites More sharing options...
Qman Posted March 31, 2009 Share Posted March 31, 2009 The intake and exhaust valves are swapped between dual and single carb heads on the inner lobes. The hydraulic lobes are meatier. I used a hydraulic cam to grind my solid lift motors cam for the hot motor. Quote Link to comment Share on other sites More sharing options...
Psyko Posted March 31, 2009 Author Share Posted March 31, 2009 When I get the chance to bring them in, you guys (Delta Cam) should be able to move the hydro lobes to the DC positions and then put a power grind down, right? Quote Link to comment Share on other sites More sharing options...
TomRhere Posted April 1, 2009 Share Posted April 1, 2009 (edited) Asking just for clarification. Lift and duration is the key here for more "performance" out of a cam grind, yes? I know that you can't have the lobe bigger than the bearing journal of a cam, so you "decrease" the base of the lobe. Therefore, "increasing" the lift, yes? Duration would be accomplished by "widening" the top of the lobe, yes? Reason for asking is, The DC cam "appears" to have smaller bases, but the "lobes" don't look any wider at the peak area. Looks like more "lift", but not to much "duration". The Hydro cam "appears" to have largers base area, but the lobes look to be "wider" at the peak area. Looks like more duration, but less "lift". Am I just seeing things wrong here? edit: I know the valve open/close timing has to do with it also, just asking about the lift/duration aspect of it. Edited April 1, 2009 by TomRhere Quote Link to comment Share on other sites More sharing options...
Psyko Posted April 1, 2009 Author Share Posted April 1, 2009 I can't exactly answer all the questions because I'm not cam expert (I know nothing more than the common sense of them really). I can pull out the caliper, to make some measurements, and try to apply some common sense, that is hopefully mildly correct, though. I started by measuring the cams across the skinniest section. Hydro: 31 mm DC: 27.25 mm I then measured across, including the lobe, so top of lobe to opposite side of cam. Hydro: 36 mm DC: 33 mm Some quick math... 36 - 31 mm means that the hydro has 5 mm of lift. 33 - 27.25 mm means that the DC has 5.75 mm of lift. So, the DC does have a considerable (?) amount more lift than the hydro, but the hydro appears to have better duration because of its extra "meat." The extra thickness means the base of the lobe is fatter, making the valves open sooner and close later (I think...). Also, because the open and close angles (angle in which the lobes ramp up and down), on both the hydro and DC cams, appear to be similar and the hydro doesn't lift as high as the DC cam, the DC has a much sharper lobe tip and shorter fully open duration. Hydro: Better duration (?) DC: Better lift If I really sat down and churned through the numbers and physics of it all, I might be able to see how the flow rates compare, but that's not something I'm prepared to do right now. Besides, to do that it would probably be helpful to have exact measurements of each cam so I can really know the area of each lobe. Basically, the question is, "what's got more surface area, a triangle (DC) or a slightly scaled up version of that triangle, but with it's tip cut off (hydro)?" Anyway, nothing truly inspiring in my ramblings, but it's fun to think about, none-the-less. It'd be interesting to see what others have got to say or if there are any corrections to my assumptions. Quote Link to comment Share on other sites More sharing options...
Phizinza Posted April 1, 2009 Share Posted April 1, 2009 Looks like the DC cam has shorter sharper lobes. Which is exactly what I thought it would have. This makes for a higher revving engine I think. Which is what these dualies are good at and made for. Rally cars need higher revs. And in ultralites and very small planes these dualie EA81's rev over 8k RPM all day long. Quote Link to comment Share on other sites More sharing options...
RenaissanceMan Posted April 2, 2009 Share Posted April 2, 2009 The intake and exhaust valves are swapped between dual and single carb heads on the inner lobes. The hydraulic lobes are meatier. I used a hydraulic cam to grind my solid lift motors cam for the hot motor. SOOO, if one were to persay... put a DC cam in an ea81 that had hydro heads, etc... you could essentially get an ea81 to run.... BACKWARDS!!! hmm... gets the gears turning in my head. Quote Link to comment Share on other sites More sharing options...
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