Gear Drive Cams revisited + S&S ignition

[David Jackson]

Dear Mike;

Revisiting the gear drive cam idea. I just got POWER SECRETS by Smokey Yunick. I glanced through the book and there is lots of great info there. He has a short section, as you probably know, on cam drives and in that section he talks about chains and their frantic gyrations inside the cam cover and their changing of the cam timing as they gyrate. I realize he is talking about very high output car motors which have much longer chains than our HD motors, nonetheless he makes the statement that he can't believe anyone would use chain drive in a high output motor.

My motor is not as highly tuned as his racers but still ...

Again (I know you hear about lots of motors), I have a 113" kit (cases are at Latus for breather install) with SE HTCC CNC ported heads and the appropriate pistons, 51mm CV, back to stock 5 speed trans, D&D Boarzilla pipe (at least until I can't hack the noise) and I am wondering what cam would you recommend, gear drive that is.

Also, is it worth the trouble and expense to have my HD ign swapped out for the S&S detonation sensing unit?

Thanks Mike;

Regards;

David Jackson

[Mike]

The T-Man 650, Redshift 657, Knightprowler 9B would all be good choices. Knightprowler has some new stuff that should also be looked at in addition to Kuryakyn and S&S. But from these we could narrow the choice based upon further conversation and modeling.
Heavy valve springs, fast cam ramps, worn chains/tensioners and rpm's all contribute to those gyrations. This is why we start to recommend chain drives with cams over .625 lift because we end up with more spring and usually higher rpm demands.
See my post to another thread about the S&S ign.
Thanks, Mike

[zigzzagz]

Mike, I've noticed that in the latus builds I've seen, as well as in the above post you tend to prefer the woods 9b cam over the 9f. I also know Dan Baisley perfers the 9b cam. What's the reasoning behind this?
Also, as far as head porting and cam preference, I often hear said by porters, "let me know what cam you're going to use and I'll port the heads for those cams." Does this actually make any sense? Do they look at the cam spex and then change their porting style to shoot for different flow numbers, velocities and such at different lifts than they normally would? Or is good porting simply good porting. For instance with a set of Cycle-Rama heads would I be more wise to go with the Cycle-Rama cams I have available to me than the Woods TW-9fg cams I chose and am currently using?
Thanks for letting us pick your brain Mike. I hope we don't overwhelm you and make you regret setting up your tech board but you've been an invaluable resource and the info I've got from you has already helped me to another 7HP.

[Mike]

We may have created a monster!!! Compliments like yours make it worth it. Just watch for brainfad on my part!
We have not seen hp gains with the 9f vs 9b when porting stock head castings. The higher TDC lifts get us into areas where the head flow starts to suffer (I.E. too tight short side raduis into the valve seat because we have to sink the valves deep into the head to get our TDC clearances). We are also usually using these cams with larger valves which complicates the matter. Some of the after market heads designed with big valves and raised ports are able to take advantage of these cams.
Some head porters include setup as part of the "porting". Some will work the ports differently depending on valve sizes which can be often a function of cam selection. These things are more a function of what type of performance we want from the bike (tq vs hp) and so cam selection, valve size, compression ratios and port shapes are all part of the original configuration considerations. I guess what I'm saying is that a good cylinder head shop would ask more than just "what cam?". Many shops offer different head configurations based upon application (Branch STG 1,2 &3; Baisley Superstock, Streetport, Pro-street and Hybrid).
Regards, Mike

[Skeeter]

Mike,</p>

I was looking at some past post and came across this post.</p>

I know we have ruled out the T-man 650 and going with the RS 657 at 10:1.</p>

How does the Knight ProwlerTW9B work at 10:1 in the fuel injected 107&quot;? I have heard the Woods cams are loud because of their shape and react violently which in turn are hard on the valve train. Any truth to this? </p>

I have the TW6 in my 95&quot; itseems to be anice improvement over the SE 203.</p>

Also do you recommend going with the chain drive camfor either 1 of these three cams as opposed to the gear drive?</p>

DoesDan set uphis Pro Street headsaccording to the cam selected?</p>

Thanks, Skeeter</p>

P.S. Yes you are great source of info thanks for all of your input.</p>

[Mike]

The TW9B is a really good 107 cam but does require 10.8-11.0 to work best. The noise is mostly a function of a loose gear drive fit. The hi-velocity ramps can amplify gear noise when too much back lash, between gears, is present. As far as excessive wear? The theory is that the higher pressure angle presented to the tappet rollers, combined with higher valve spring pressures for valve control, can cause accelerated wear on these parts. This may be true for single cam (EV, Shovelhead) motors that have cams with smaller base circles than TC's. The larger base circle used on TC's reduces this affect and allows for faster ramps without the associated wear. We have not seen failures in TC's as a result of hi-velocity ramps. I will typically recommend gear drives when valve lifts exceed .625 (with a discussion about possible mechanical noise and additional cost).
Thanks, Mike

[Skeeter]

Mike,

I am thinking it will be best to stick with the RS 657.

You mentioned the RS 657 works best at 10.3 but would be okay at 10.1.

Is there a lot of difference between 10.1 and 10.3?
Are there any cons with going to 10.3 as opposed to 10.1 such as being harder to start, running hotter, and keeping the motor tuned or the use 90 octane pump gas.
Here in the flat lands of Texas most places sell 90 octane gas.

Thanks, Skeeter

[Mike]

The 10.1 will be fine. My 10.3 rec. is based on computer modeling and .2 diff. would have little affect.
Thanks, Mike