Jim,

Learning about cams is tricky. I learn every day, as I am lucky to live near Torque Inc.

We all, eventually learn that intake close is HIGHLY important. This determines the dynamic compression, because static compression means nothing at all. Next things would be lift and duration. Fairly easy subjects. Intake close is when the intake closes when the piston is going UP on the compression stroke. A close of 25* closes way sooner than a close of 45* The 45* close bleeds off a ton of compression, see? AT the same time, most do NOT want a close of 25* because it DOES build too much compression and the CCP could be well north of 225 ccp. DJL like to state dynamic compression still in term compression uses, like 9.3:1. I express dynamic compression in Cold Cranking Pressure. CCP. CCP is easiest to understand, because that pressure correlates to what a compression gauge reads while cranking the engine. For a street touring bike... I like 185 ccp to 190 ccp. That will make for a peppy ride with a somewhat decent bottom end. A cam that closes too early, will have CCP like 225 and one cannot tune that well, be a ping monster, and be very hard to start when hot. A cam that closes too late, the ccp will be down to 150ish, make NO power at cruise, and also suck to tune.

So, using tools found on like Big Boyz web site like twin cam compression tools can help figure that ONE piece of the puzzle.

Most simply worry about intake close and compare none of the other numbers

But then it gets trickier. LSA becomes important and so does overlap. 120 and 103 engines will like very different LSAs for sure. Same with a 95 -vs- a 103. Even though the piston is the exact same size, that increase in stroke makes the cam choices vastly different.

Descriptions in catalogs are basically useless. ANd also very very useless is making ANY kind of assumption about how companies market different tunes for their kits. YOU make assumptions and, first thing in this learning curve you are on, is to STOP that completely. Seriously, too. I used to do the same things but have been bit HARD, cost me a lot of money, and now-a-days, I do my homework instead of letting others do it for me.

I like you and like to see a guy strive for more knowledge. So... consider these tips from me on how to continue.

My 'go to' cams are for a 96" bike: Andrews 48s. FOr a stock 103? That would be a TMan Torquester 555 (way different than Woods 555 for sure) or a Torque Inc bolt in for a 103. Every tuner will have his own favorites based upon his own personal experiences. Except for possibly SE 204s, I, myself, do NOT like SE cams. You can see that Mike does not either. Just MAY be something to all of that....... ya know?

Oh, and 'proper' break in can be had in ONE day! That is completely BS about waiting 500 miles before a 'final' tune. In fact... waiting that long can do some serious damage to an engine, and me? I have not seen damage from too lean... I HAVE seen damage from too rich. killed the cylinders completely. I do NOT mototune either. I go by the standard S&S method of heat cycles. But, if started early enough in the day, one can do 5 heat cycles and ride the bike a little in one day. Next day? Tune the bitch. ONLY thing that needs broke in on a HArley engine is the rings, and after 5 heat cycles and a small ride of up and down from 3500 a few times, the rings ARE set.

Oh, and so you know... there is NO calibration for a Stage 4 race kit, only Stage 4 street kit available from Screaming Beagle. It what I am saying about assumptions on your part. Know for what you speak, ok? Don't assume.

 

work_truk: Thank-you! That was very helpful. I think I am beginning to get at least a glimpse on cams.

The lack of a Stage 4 canned tune from HD is puzzling. On the one hand, they can simply say" hey, it's not a kit intended or marketed for the street, and a racer will want to do his own tune anyway". On the other hand, you'd think they'd at least provide SOMETHING to start with.

I did notice though that Mike Lozano told me flat out he would simply start with anything that was in the ballpark at all, and indeed he looked in his library briefly and started with a 110 cubic inch tune which he quickly modified as needed.

Obvious question for me to ask after your explanation on CCP. Is it "better" (or not) to get more CCP, because that "should" provide more torque, provided you don't trigger either pinging or very hard starting? Or, are there other considerations that sometimes make that unwise?

Jim G

 

With ccp, bigger isn't better. There are 'ranges' one would want depending upon how the bike is ridden. I like 185-190 or close to that for everyday street bikes. A dyna can have a tad bit more due to its lesser weight but not much.

HiPo street builds or fast baggers will tend towards 195-205CCP, but that can be a premium gas dependent bike and won't do all that well in like WV. These bikes will usually NEED compression releases. Same with installing SE 255 cams in a 103. Sigh... hot starts are fun without compression releases. A higher CCP cam (using early closing) makes some power down low, but peters out up higher. Specific built engines, like hot bagger engines, will use 11:1 or even 13:1 pistons and still have around 195 ccp, due to the later closing cams. The later closing cams are better for top end and high mid ranges. AS when revs climb the cams will loose a little of the ability to bleed as much compression. My 120r uses a 66 closing cam, for example.

Put those 266s in a stock 103? Might not run at all!

I usually recommend a ccp of about 185. That number will be based upon static compression and the closing of the cam.

Learn to use this tool correctly, and one can come pretty darn close to figuring out what any build will have for CCP when done.

http://www.bigboyzheadporting.com/TwinCamComp.htm

The various 'ranges' for dynamic compression is learned from others or trial and error. The only true thing is a cam cannot be perfect for low, mid and high. The other numbers will come into play, too. That is why all decent builders and tuners will ask, repeatedly... How do YOU ride your bike? Most want low and mid... the areas where we all normally ride. The mid to high cams will be soft on the bottom, but those guys will keep the revs up.

Here is a sheet for the Torque Inc 561-1. This cam pulls decent torque right away and carries out decently. I like anything that can reliably cross 100 ft lbs at 2500 rpm. THAT make for a lively ride, and you can see this cam pulls decent to red line, too. THAT has to do with LSA, etc. This is STILL a low to mid cam., you can see it, right? It just doesn't die off too bad.

This cam closes a little late... 39.5* compared to cams marketed low-mid. YOU can see why I like it, I'm sure. This is a pure bolt in cam with no headwork, etc and a Dragos pipe on it.

Red line is untuned, blue line is tuned.



And, Jim... here is another tip. Some dynos read high. Why? Some sell speed and not tuning. The better the numbers, the 'better' their parts may be, see? This was tuned by Chad at Roeders, and a shop like that is beyond reproach. You won't have an 'eye' for this crap until you look at enough sheets and learn what places always have the highest numbers.

 

Work_truk: Your postings here today are terrific. They should seriously be considered as "sticky" material.

You are providing an actual "been there and done that" perspective, and are not doing so to try to sell anyone anything. That gives it real credibility.

I can see where that shape of torque and power curve is nice for a bike that, for example, has the gearing that current HD models are coming with. Even in 6th at 60 mph (2200 rpm), the engine here has about 37 rwhp available. A quick downshift to 5th gets you to over 50 rwhp, which will accelerate the bike very quickly (when I was in college in the early 1970s, the current "super bikes" made about 55 rwhp at PEAK rpm).

The area under the curves is also good. And there are no unexpected peaks and valleys in either curve.

What displacement is the engine that produced the dyno chart you used as the illustration?

Jim G

 

I told you it would be better to let Truk have the floor.

 

Just a quick note on my tuner, he is a guru, a very gifted tech. He made the bike that was a nightmare to ride from the dealer into an extremely rid-able bike. Like I said I think in the hands of another he or she would probably love it. I think its almost the best one could get from a stage 4 in regards to ridabilty, its just not for me. Carry on chaps )

 

And then, you can use a little cam(early close/short lift)with a smokin' set of heads, surrounded by a good intake/exhaust system, in the hands of a skilled tuner, make some outstanding power.
Scott

 

Thats a stock 103

 

I may be speaking "out of school" here and Jim can spank me if I am but what about asking Jim to download and send you his map? I am not sure how that works with the SEST but I know it could be done with the SERT.

Then your tuner could see the difference in his map and Jim's; he might even learn something. Just a suggestion from a backyard shade tree hack.

 

That's a pretty good idea, djl. I would be happy to email my Power Vision file. The OP will need a Power Vision to read it, and with the length of this thread, I have forgotten whether or not he has one!

If the OP wants a copy of my file, he should PM me his email address, and I will email it (you cannot do attachments in PM).

Jim G