With the 103 cams intake close at 33 the 9.7 static would be darn near perfect for pump gas/hot starts. Going to 10.3 would bump tq a few but at the cost of a ping machine, especially factoring in carbon build up down the road would put you up to about 10.5 static, too high for this cam but great for a wide range of others..as mentioned.

 

You're right......third set of cams. At least after this deployment I'll be able to afford these mistakes. 10.5 to 1 it is.

 

You know,,,,,, You're right..... I am tired of conforming and 9.7:1 is a pincher but if you want to optimize you need to know how to tune. I think that even 9.85:1 is doable on pump 93 gas. IF and again IF you know how to tune...... it'll be a runner without complications....

 

If you go the 10.5:1/585 route, you can add 1.725 ratio rockers at a later date for even better performance (very close to the Crane 296) without tearing the motor down beyond the rocker boxes.

 

Damn it! Been toying around with the idea of a similar setup ....107, worked heads by hillside, tb upgrade( unsure as to what yet) and the tman 590 cams. Good luck on the 3 rd set of cams.

 

I know you are getting conflicting advice but a word of caution.

You have relied on the S&S guys in the past and you can see what that has cost you in time and money. Not saying the tech doesn't know what he is talking about but youi need to figure out a couple of things before S&S goes to work on your heads.

First thing you need to know is that if you are not running the numbers and calculating CR, you should familiarize yourself with the BigBoyz compression calculator and start running the numbers. Forget about static CR for a moment; it is just a number. The motor never sees static CR but operates under dynamic (corrected) CR and cold cranking compression (CCP). Most builders have established a "safe" range for both that will provide a customer with good, dependable performance without tuning, rideability issues. That range is typically 9.3-9.5 for corrected CR and 185-195 for CCP. The first step in developing a build plan requires establishing how the customer rides the bike, i.e., where does the customer need the power; very different for a touring guy that travels two up and loaded than for a guy that want to drag race from light to light. Once the riding style is determined, the next step is selecting cam shafts that will deliver the power where the customer needs the power since there is not cam shaft that will deliver constant power from idle to WOT. You are way beyond the first two steps and are now going backwards since you still haven't settled on a cam set.

A couple of words of advice that you can take or leave.

1. Don't let the S&S guys work on the heads until you have decided whether you are going to run the MR103s or the S&S 585s; the work will be different for each.
2. Find out the dome volume for the pistons and assume that you will run a .030" or .040" MLS head gasket; not the .045"; assume that your deck height averages .006".
3. Insert the required data in the BigBoyz calculator. Select a 107" configuration but change the bore diameter to 3.930" to keep displacement at 106" and use the piston dome volume that S&S will provide and the 85cc chamber volume that S&S is suggesting for the MR103 cams.. Run the data for both cams and you will see the difference in corrected CR and CCP for both. I think you will see that at the 10.2-10.3 static that S&S is suggesting, both corrected CR and CCP are a bit on the high side. You can change head gasket from .030" to .040" (.030" would be better IMHO) and change chamber volume to come up with a combination that produces a corrected CR in the 9.3-9.4 range and CCP less than 195 or less.
4. Decide on a cam and based on that data and then you can direct S&S on what chamber volume you need for the desired combination.

You need to approach this methodically or you will end up in the soup again. You need to know the dome volume of the pistons and choose a cam before S&S does any work on the heads. Personally, I would not proceed any other way as any other way is still hit/miss and the outcome unpredictable but that's JMHO.

 

DJL,

As usual, thanks agin for the advice, you're absolutely right. I didn't rely on the S&S tuner, I verified on the BB site. I called the techs, the flat top pistons have a -2.0 dome. If I have them deck the heads to 85cc and run the 585 cams, I will be at a corrected compression of 9.31:1 and a cold cranking compression of 193.4. That sounds about right. The other option is the 570's, according to the calculator, they would put me at 9.53 to 1 and CCP of 199.2. Is that too high; have a chance of pinging with 93 octane? Whatdoya think?