SS585 to TW55 comparison 95"

[Y2KRKNG]

Another "which cam" tread, hopefully you don't mind.
So at 60k my crank went south so I did a complete rebuild with trued and welded crank, new jugs, new everything in cam chest, Branch proprietary pistons(CP), and reused their #4 heads from back when they were called Flowmetrics.
I kept the rebuild basically the same configuration mainly do to cost(about $1500 total) with the exception of cam. I went with the Andrews 55 on the recommendation of head porter Branch O'Kieffe(RIP) and this is my take and concern with it. With the 585s the exhaust sound was intense and sounded powerful with a "sledge on an anvil" crack to it, this TW55 sounds mild and weak and almost reminds me of when I had that Supertrap on my bike.
The bike runs good and pulls hard lower on the band which is real nice with my 3.15:1 and 34 trans sprocket(I like to cruise fast)but im just not used to this new sound and feel.
Another cam that was mentioned by Branch was the Redshift 577, Said its been showing nice peak numbers on a 95", but it was tough to find that one in Cali and it was a couple hundred more then what I found the 55 for.
I'm set at 10.6-10.7:1, hit 6krpms every time it comes out of garage, have gearing on the higher side. What say you on a replacement cam?

[Hossamania]

I have a 55, and am interested in what comes of this discussion. I'll be due for an engine refresh sometime soon, over 110,000 miles on this motor now.

[rigidthumper]

The S&S 585 cam opens the exhaust valve earlier than the TW55s, so there's more combustion pressure present, hence more sound. As you've discovered, there is torque to be gained by opening the exhaust valve later, most find that costs HP on the big end, and changes the exhaust note. As far as peak numbers, all three cams should be very close on the dyno.

[838]

tman 590???

[Y2KRKNG]

The S&S 585 cam opens the exhaust valve earlier than the TW55s, so there's more combustion pressure present, hence more sound. As you've discovered, there is torque to be gained by opening the exhaust valve later, most find that costs HP on the big end, and changes the exhaust note. As far as peak numbers, all three cams should be very close on the dyno.

Well that's nice to know. No real complains from the mild mannered TW55 so I guess ill try to suppress the itch for a while more.

[Hossamania]

Cough, cough, nitrous, cough...

[wfolarry]

The S&S 585 cam opens the exhaust valve earlier than the TW55s, so there's more combustion pressure present, hence more sound. As you've discovered, there is torque to be gained by opening the exhaust valve later, most find that costs HP on the big end, and changes the exhaust note. As far as peak numbers, all three cams should be very close on the dyno.

I didn't read it that way & I don't see it that way. Care to explain?

[rigidthumper]

With the 585s the exhaust sound was intense and sounded powerful with a "sledge on an anvil" crack to it, this TW55 sounds mild and weak and almost reminds me of when I had that Supertrap on my bike.

The bike runs good and pulls hard lower on the band which is real nice with my 3.15:1 and 34 trans sprocket(I like to cruise fast) but i'm just not used to this new sound and feel.

I believe the difference in the exhaust note is because the 585s exhaust valve @ .053" opens at 60 degrees before BDC of the power stroke, while the combustion event still has some more pressure left to exert on the piston, but the opening of the valve causes a rapid release of that pressure, called blowdown, that immediately reduces the push on the crank (Torque).

Blowdown on the TW55 cam @.053" occurs 8° later than the 585s, so the pressure (that created the louder exhaust note with the 585s)  instead continues to push on the piston for a little bit longer ( little more torque to be gained) and now the piston is closer to BDC when the valve opens, so the blowdown event is less sharp, and less loud.

As i understand it, on the big end RPM, as things are happening faster, you don't want residual pressure fighting the piston on the way up during the exhaust event, so opening the exhaust valve earlier helps that process.

I realize 8° difference in EVO cam timing may not seem like much, but I think it's enough to be noticeable.
(I also realize I may be completely wrong)

[wfolarry]

You're right. I was reading it wrong. Too early in the morning I guess. I thought you wrote the 585 was more of a torque cam. 

[Y2KRKNG]

Cough, cough, nitrous, cough...

Oh now we're talking. Just a little squirt should be fine, lol. Hidden bottle of course. 

[Hossamania]

Cough, cough, nitrous, cough...

Oh now we're talking. Just a little squirt should be fine, lol. Hidden bottle of course.

I always wanted to, but no way a motor lasts five miles with me if I can hit that button at will!