SE 103" build
#21
10-09-2008, 10:51 AM
Tourer
Join Date: Aug 2008
Location: Diamond bar, California
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I had several discussions with Kevin at Head-Quarters and really didn’t have the time to go into all the details. I’m not an engine builder, head designer, or expert in fluid dynamics so you’ll get my minimal technical explanation of our conversations. I also thought the HQ-575 would be the best cam for my build based on the combustion chamber size and larger valves. But in this case cams are not like dicks, bigger is not always better. With that said, to get a complete fill on intake I figured it would be best to open the valve farther and keep it open longer. Kevin said you need to also consider the intake charge velocity in that equation. You may actually get less fill/charge for a longer time at a lower velocity than a shorter time at a higher velocity. In this case if the lift is decreased the velocity through a smaller opening is increased. Also the lobe placement (the points at which the valves open and close), valve timing duration, overlap, LSA, LCA, etc, etc, must also be considered. He said with the HQ-500 I’d get more torque at a lower RPM than the HQ-575 and maybe I would have a slight decrease in HP at a higher RPM. Since I really don’t care about a small HP lose at 6000 or so RPMs, I’ll take the torque increase at a lower RPM. Since I don’t have the technical knowledge, experience, or design expertise to argue the point with him, I decided to accept his recommendation and go with the HQ-500.
Thats great! I was thinking that you were running HQ heads instead of the SE ones.
the prognosis is spot on.
#22
10-09-2008, 12:10 PM
Join Date: May 2007
Location: Evans, GA
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So the larger (98cc) hemispherical combustion chamber, by itself, increases the distance from the top of the piston and loosens the quench area. But doesn’t the domed piston with the raised squish band and the raised top (center) of the piston somewhat tighten the quench area? I realize that the angled design of the HEMI combustion chamber does not give you much or any piston to combustion chamber flat surfaces. So in that case the wedge design combustion chamber provides better squish and tighter quench than the HEMI but the heads don’t flow as well because of the valve placement. Since all HD OHV heads basically have a HEMI combustion chamber what is the biggest issue with these particular heads. Is it the larger combustion chamber and/or the combustion chamber configuration?
#23
10-09-2008, 12:22 PM
Join Date: May 2007
Location: Evans, GA
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#24
10-09-2008, 12:52 PM
Road Master
Squish
This is why we like the stock TC combustion chamber, not the SE or S&S. Very easy to get compression and squish area and no pinging. Detonation is a result of heat and pressure, we know how to take heat out of these engines so we can up the pressure without pinging.
The valve spring to rocker box clearance is easy to see and adjust with a ginder.
The valve spring to rocker box clearance is easy to see and adjust with a ginder.
#25
10-09-2008, 01:41 PM
Join Date: May 2007
Location: Evans, GA
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I can see with the bathtub style combustion chamber there is a flat surface on both sides of the combustion chamber that matches up with the flat top of the piston. Makes it much easier to determine squish and quench area. Thanks for the info on the clearance problem. One more question, I’m current running a PCIII and have been very satisfied with it so far (easy to install, adjust, and fine tune). The local HD dealer will not or cannot tune a PCIII, they’ll only work on bikes with the SE Race Tuner. That hasn’t been a problem because I’ve used maps from Jamie at Fuel Moto and then done some fine tuning based on sound, feel, performance, and plug readings. With the new build I have considered switching to a SE Pro Race Tuner or maybe a ThunderMax. If I keep the PCIII or switch to the Race Tuner, Thunder Tower HD in Columbia SC is good at tuning both. If I install the ThunderMax and can find a good base map it may save me time and money in Dyno Tuning. I like the idea of running a close loop system with wide band O2 sensors and auto tuning. What is your experience and/or opinion on that subject?
#26
11-26-2008, 08:21 AM
I had a kit put together by my dealer this summer. I went with the 103+ heads and ditto pistons. As for cams I went with Red Shift 627 and D&D Fatcat exhaust. I ride a 07 Low Rider, and I couldn't be happier with the result. It took a little getting used to to have to rev the engine higher to get max output. Around 3500 rpms things happen really fast. With a tourer I probably would've chosen cams that gave more a little earlier. I havent had the final tuning on the SE Race tuner yet, but currently I'm running around 109HP and a little above 100lb/ft. The builder won't be happy before he sees 110HP. To acheive that I probably have to find an air filter that is better than the SE one.
The engine is really good. No issues just putting around town and with real grin-factor when unleashing the power out on the open road.
The engine is really good. No issues just putting around town and with real grin-factor when unleashing the power out on the open road.
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