I'm thinking of changing my cam this winter. I want to go to a Andrews EV-13, from a 20 somthing.... Not too sure of the #s.

I have all the goodies already, Heads, S&S Super E, Ignition work Ect.. My power comes on at about 3100 rpm. and pulls pretty good all the way up, but it rides like a 2-stroke dirtbike with this cam. I want the power to come on about 1500-1700 rpm.

How much will a cam swap effect fuel mileage. I can get 48- 55 now if I keep it below 75 mph.

V2

 

give hdwrench a shout.........he is definitly a guru!!!

 

The most important cam timing event is when the intake valve closes. The intake closing point determines the minimum rpm at which the engine begins to do its best work. The later the intake valves close, the higher the rpm must be before the engine gets "happy."

High rpm cam designs often perform poorly in the rpm range associated with ordinary riding. The problem with such choices is that the engine seldom spends time in the rpm range favored by such cams. Unfortunately, in the quest for maximum power output, many-too-many Harley owners choose a late-closing, high-rpm cam for their engine.

A majority of any Harley motor's life is spent in the mid-portion of is rpm limits, between 2000 and 4000 rpm. At open-road cruising speeds, that range is more like 2500 to 3500 rpm. With current Big Twin gearing, top gear at 2500 rpm returns a road speed of 60 mph and 3500 delivers 84 mph. Riders sometimes "putt" around at 2000 or less. Even when accelerating to cruising speed, few of us use more than 4000 - 4500 rpm as a shift point. Very seldom, in day-to-day use, do our engines get near 5000 rpm, let alone 6000.

Even the mildest of Harley-Davidson's aftermarket cams (Evo or Twin Cam) do their best work above 3000 rpm. At 2000, the majority these cams seldom perform as well as the stock cam(s).

The rpm at which a Big Twin gets "happy" can be predicted by the closing point (angle) of the intake valves. The angle is expressed as the number of degrees After Bottom Dead Center (ABDC) that the valves reach .053" from being fully seated.

30 degrees = 2400 rpm
35 degrees = 3000 rpm
40 degrees = 3600 rpm
45 degrees = 4000 rpm
50+ degrees = 4500 rpm


These relationships are approximate but should hold true to within 200 rpm or so. They also assume that all other tuning factors, exhaust, ignition, etc., are operating correctly.

If you have one of the late-closing cam designs installed, say one that closes the intake valves later than 40 degrees, then you cannot expect excellent performance at 2000 rpm. No carburetor adjustment, ignition adjustment or exhaust system can change this.

 

Souonds like an 80" EVO pretty much like mine (94 FXSTC)...besdt all around cam (IMHO) is the Andrews EV27...add a Crane Hi4 single fire and you'll be set to be a streetlight stampede champion!

 

I'll double what nmfxstc said. Had the same setup in my '97. It was a sweet setup. I was running it with an S&S Super E and V&H Longshots. The only thing I ever found myself looking for was another gear on the interstate. I can't tell you how many times I was coming off an Interstate ramp at about 75 and squeezed the clutch, kicked the gearshift, and found out I was already in 5th.

 

Allright, I got ahold of the previous owner that did the mods on the scoot. As far as ignition goes all that is done is a 1200 Sportster ignition module. I'm really concidering the Hi 4 set up, and giving the EV27 cam another season to try and please me.

However I do need some help ordering the right stuff, what exactly do I need?

Drag Specialties Fat Book Part #s

Hi 4 Singke Fire Ignition kit
P/N DS-325770 $ 417.95

Fire Ball Hi 4E ignition module
P/N DS- 242336 $ 289.95

Obviously I need the Ignition kit, is the module necessary?

 

The EV27 is just about the best all around cam for the EVO...with a little head work and the igntion, it makes power in all of the ranges you'll ever need. 2nd choice would be ether the EV3 or EV13...just my take.

On the Crane...you'll need the module and a coil.

That Sporty mod doesn't really bump the ponies that much, all it really does is change the rev limiter...and you can do that with the Hi-4 as well (better....the Sporty module just sets it at 6,000).

Sounds like you need a good wrench to set it up and tune it for you...my 94 FXSTC has SE 10:1 heads, EV27, Crane Hi-4 single fire, Yost POwer Tuve and a modified CV carb, Python IIIs and hauls ***! get a decent wrench to tweak that EVO for you...you'll be waaaaaaaay happy!

 

Thanks, nmfxstc!

The reason I'm picking on the EV 27 cam is my Dad had a 94 TC that had a EV 13, with Branch heads, Kirker slip ons, S&S Super E, I think single fire ( Orange coil ??) and other stuff. That 94 would pull like crazy out of the hole up to 4500 rpm and get sideways on 1-2 and 2-3 shifts, and got better mileage touring with a friend on a stock carbed Evo Ultra. And no downshifting to pass a semi on the E-way.
That 94 was and still is (a friend of mine has it) Awesome! The way that thing barks, like the Hounds of Hell!!

The 96 I have now belonged to a work buddy of my dad thad tried copying the 94, its close but somthing is missing in the setup, Ignition is on the christmas list now, if I'm still wanting more or a different powerband after that then a cam change will be in order.

 

As the bike sits now, cold starts the engine bucks back at the starter, and at times backfires out the pipes at start up after work. That Ignition set up may cure alot of that stuff.

Gotta find me a Dyno!

 

Yup...spunds like a timinmg issue.

BTW...my FXSTC is up for sale!