Sorensen Performance
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Frequently Asked Questions

Q. Will these heads bolt onto my stock Motor?

A. Yes, with the use of stock low dome pistons. With proper engine building you can shorten the barrels to effectively give you a .035 squish band giving you maximum results with a compression increase of .5 to 1 point depending upon the engine configuration.

Q. Why are these heads so much better?

A. Because these heads have a Unique Peanut shaped combustion chamber and dual 30 degree squish bands that promote excellent turbulence and, a complete burn of the air/gas mixture. Our chamber is derived from hours of on the dyno research to bring you the best chamber Period! Our chamber is so efficient that generally with proper squish of .028 you run air fuel ratios of 14.1 at WOT for best power.  This allows cranking compression of around 210Psi on pump gas with proper tuning and as high of 240psi has been run on pump gas with careful tuning. Early in the 70s a few savvy racers figured out that poorly designed combustion chambers that were prone to poor burn patterns, puddling, and detonation. They tried to cure this with adding what is called squish slots to promote swirl it was a poor mans cure for a badly designed combustion chamber. With over 30 years of building race motors and racing background , I have employed all this knowledge into the design of these heads, which simply cannot be achieved with a few hours in a CAD program. We continuously are striving to make our heads even better and there have been new improvements on valve seat angles and shape that has allowed the CFM to increase almost 10CFM from when we first introduced them.. and there is more research continuing as you read this.

Q. Does a bigger valve kill Power and Torque?

A. No! Being as we have in house dyno equipment we have done back to back testing and there was no loss in power or tq anywhere in the powerband with increasing valve size, Power and Tq climbed on every increase in stage size of heads with bigger valves. Our ports are geared around peak rpm of 6000 for HP.

Q. Why doesn’t All the competition flow test their heads or dyno test?

A. Simple, because they don't have the PROPER equipment to FlowTest, WetFlow test or even run in house Dyno testing on their products. Companies like S&S do have in house dyno testing. Sorenen Performance is dedicated to making a product that makes the most power on the market period. We do Wetflow testing , Airflow testing and Dyno testing to make our product the best it can be.

Q. There is a company claiming that airflow is not important to make Hp and only velocity counts.  Is this true?

A. This is absolute mis - information and False!  While velocity is definitely an important role and very particular in Harleys because to much velocity and the intake charges goes straight out the exhaust valve. Different velocity heads require different cam profiles to make them work properly.  A motor MUST have X amount of air and X amount of cam and X amount of compression to make X hp.  Companies like Airflow Research and Spier Racing heads, Reher Morrison to name a couple all hand port heads then dyno test, wet flow test then they go to cad and are then cadded for development in CFD. At this point the port is then machined and back onto the flow bench to verify the programming is correct. Then they go back onto the dyno for more extensive testing and this process goes back and forth between flow bench, CFD, and Wetflow testing and then Dyno testing. A port drawn in CAD and only done in Computational Fluid Dynamics fall short in the real world, which is why all the additional testing and hand work is needed. You won't find a competitive motor or race team that doesn't make use of this. Be wary of companies that suggest this ISN'T important and can't even tell you a flow number.

  A good head should make clean power all the way to redline, heads with port issues generally fall flat early in the powerband. Port size is important as well as cross section.  This simply cannot be done with just drawing a port in CAD and machining. Sorensen Performance employs all these tools at hand to develope our products.

  Wetflow testing IS one of the important things to be done for a quality port. Race teams and Top head designers spend thousands on wetflow developement. It actually shows you how the fuel charge is entering the cylinder and a simple thing as changing the Valve angles with a different profile cutters can kill off CFM which directly is related to HP as well as make the fuel charge break into droplets causing puddling and turbulance causing the airfuel mixture to drop out of suspension, making the motor less efficient, lazier, require more timing and the need to use more fuel and jet to make power.

  A Harley engine needs approximately 4 cfm to make 1 HP. The higher the Hp number after 90hp the harder it is to make HP, it is realtively easy to make a Harley in that power range with mildly reworked stock heads , After this it becomes difficult to make power , this is where true engine builders shine. Also the valve seat angles relate to how the air acts past the valve and enters the chamber and cylinder fill.

Q. What is the difference between 3/8” valves and thin stem valves?

A. We use thin stem valves which are the same diameter as the Evo/Twin cams for lighter weight and better flow. We also use a inhouse made profile guide for better flow as well, made from Aluminum Bronze for very long life and durability. The 3/8” valves are big and heavy which impedes flow and adds unneeded weight in the valve train. The Shovelhead was NOTORIOUS for wearing out top ends and wearing out guides. The 3/8 valve in the short guide just plain wears out fast, add in poor valve angles and they wear even faster!  We use the .310 stem for EVO/Twincam lifespan even with .650 lift. The guide hole is a standard Evo/Twincam  size so if you ever do wear them out, they can be replaced with off the shelf items. Manley will also sell you replacement valves for the heads as well. So no worries about non obtainable parts.

Q. Can I bolt on a stock intake and expect maximum results?

A. No! By nature the shovel intakes do not flow well. Both the Super E intake and the SuperG intake need port work. The SuperE intake responds OK with porting and will  flow of up to around 240cfm before going turbulant. The SuperG intake requires an extensive amount of work to achieve real airflow. This work will require welding, epoxying, porting and extensive flow bench work to achieve. We have done the work for you, SpChoppers offers a billet SuperG intake that has over 100hours of flow bench invested into it. The manifolds are CNC machined and replicate all the hard work involved. They work great on a modified stock shovel as well.

Q. Why should I consider using SP Chopper Evo conversion blocks?

A. The geometry of the shovelhead is quite poor. However, by using the conversion blocks, you can use updated Evo lifters and more aggressive profiled cams. What this does, is allow you to make more power down low and up high with a smaller cam. Please see our attached dyno sheets. Our blocks are computer designed and mocked up in Solid Works and the lifter bore angles have been corrected to be the best they possibly can be. Our parts are machined in small runs and held to extremely tight tolerances and are truly the best on the market.

Q. Do the competitors' heads you mentioned really run hot and why are the SP heads a better choice?

A. Yes they do. When heads are made into a bathtub style chamber, they retain too much material, and as a result, it causes overheating of the heads and as mentioned in our brochure can result in the inserts becoming loose and falling out. Our SP heads are designed with a unique peanut shaped chamber with just enough material in the critical spots, to get things moving. We also added the much needed fin area on the top of the head, to pull heat out of the center and thereby reduce overheating. In addition, we also increased the Size and Thickness of the fin area on the entire head to further reduce overheating. Thin scalloped out fins reduce the heat sink potential and make for a hotter running engine.

 Q. How much power can I really make with these heads?

A. There is enough room to install a 2.250 valve and [email protected] 28" on a 88” motor and, with proper building techniques and the proper selection of parts, a person could easily achieve 120 hp plus on a 93" using proper fuel and components. And, as we have shown, it’s really quite simple to build an engine capable of 108 hp on straight 92 octane pump gas with not radical parts.

Q. I don’t have the tools to build an engine like this. Do you custom build?

A. If we have time , I will custom build an entire engine and dyno it before it leaves to ensure everything is good.

Q. I have been told that HP numbers will vary from place to place. Is this true?

A. Altitudes, temperatures, the tuner, dyno operator, type of oil, engine temperature are all factors that need to be taken into consideration. Our engines have been tested on other dynos and only varied from 0 to 3 hp, all depending on the factors taken into consideration.

Q. What type of carburetor works best?

A. We have dyno tested numerous carburetors and we have found that the essentially what the motor sees is total airflow. There are minor gains to be had brand to brand. On smaller engines a big bored CV is hard to beat, it gives great response with no restriction on Wot power.  Your basic G carb with a thunderjet is pretty hard to beat for simplicity and ease of tuning. A 40mm carb will become a restriction at roughly 84hp.

Q. Are there any type of warranty on bottom ends or complete engines?

A. Baseline engines or bottom ends have 5000mile or 6month warranty. 128" and 142" All out highperf engines do not come with a warranty. Any Disassembly of Engines or Lower assemblies or Modifications without prior authorization will effectively terminate and make all warranties null and void. 

Q.Can I return special custom ordered parts?

A.We do not return custom ordered parts.  They are custom made or ordered  to your specifications. Please make you get your order right the first time =o).

Q. Can I order a set of heads and get them in a couple weeks?

A. Unfortuneatly no. To preserve the utmost highest quality of my products I have moved all machining and heat treating in house and do everything myself. As I have many orders to fill, it may take a bit of time for me to machine and complete your products ordered, be rest assured that as much care and time is taken in each order to provide you with the best product possible. Do remember these are CNC machined parts and take a very large required runtime and handwork to prouduce each product.

Q. Can I use my stock HD bolts or a aftermarket bolt such as S&S with the Harley thread pitch

A. NO NO NO NO ! The heads are 7/16x14 coarse thread pitch. Any such attempt will damage the threads Immediately!  We do not use fine thread bolts or fine thread inserts because the thread engagement is so minimal they pull out.

Q. I notice that the bolt holes for the rocker boxes are not threaded to the bottom is there a reason for this?

A. Yes , they are purposely not threaded to the bottom to allow for wear and tear over the years and over torqueing , that if the threads do get damaged over time instead of immediately having to helicoil the hole you can run a roll tap down and voila now you have more threads and just replace your bolts with a longer bolt an easy repair at home and your back on the road. If you feel you want a bit more thread you can easily just thread in a roll tap quickly and add a few more threads.

Q. Can I tq the heads to stock 65lbs tq spec ?

A. NO NO NO NO ! Do not tq the heads anymore than 40ftlbs! You will pull the threads out of the head.

Q. The threads looks different than normal threads, are they double tapped or wrong?

A. The heads are tapped using a Roll Tap/Form tap that molds the aluminum into a shape and they have a different look to them and you can actually see the center of the thread looks like a gap at the aluminum is rolled together into a shape.  A cutting tap cuts the aluminum and has a different look and a weaker thread.

Q.  Should I lube the bolt?

A. I like to use antiseize on the bolt to prevent galling of the threads, also its a smart idea to thread the bolts your going to use in first, some bolts may possibly need a die run down them quick to chase the threads.

Any modifications , repairs etc void all warranty unless prior approval is agreed upon by Sorensen Performance.

We're committed to helping you build better power, better performance and a better ride!