Frequently Asked Questions

What is HD Street Performances’ mission?
We want to help riders put the fun into these motorcycles. They come from the factory in a very detuned state and with some sensible upgrades they can provide a much more enjoyable riding experience. Most of our customers are interested in just fixing the torque curves so the bikes have a much better feel of power stop light to stop light or on the road passing a truck or in similar situations. A small percentage of what we do is serious performance work for the riders that want to enhance the power beyond just a better torque curve.

Why the name change from Head Designs by Dewey?
After 6 years in business simply stated our product is very dissimilar to the original Deweys product. I have done flow development and dyno testing and changed the product to better align with the market and riders needs. Our current “Street Pro” package for example performs equal or better than the original “Pro Street” head work and does that at a greatly reduced price. New guides are provided on all but the “Blueprint” packages and flow sheets provided again for all packages except the “Blueprint”. The ports have changed, the parts are different and the machines / tooling used to perform the work are improved.

What is so great about “Porting by Hand” verses CNC porting?
Nothing in my opinion! Both can work well.
At this time all of our heads are Hand Ported. I have established dimensions I use and consistently can duplicate the product as verified on a flow bench. I have no issue with CNC and frankly may look into buying a machine in the future. Let me be clear however this is a move to improve turn around time and minimize the amount of arduous labor not as a product performance enhancement.

Do you use a Flow Bench?
Yes. We own a Saenz S-600 that has been improved with higher power motors to allow testing up to 50” H20 pressure. Our bench is calibrated using PTS calibrated orifice plates and we go to great lengths to assure our flow numbers are accurate. That said we use our own fixturing that may not be the same as used by others therefore results may vary. Flow numbers do not sell our product. We use the bench to verify results, a QA function, not to advertise. Higher airflow is no guarantee of added power and torque. We show average flow numbers, not just peak, which are another important factor in the performance potential offered by the heads.

How much power will your heads make on my bike?
We post dyno results in order to show what others have achieved. Optimizing the head is only one component that no longer is a constraint to added power and torque. The remaining parts that are matched with the heads are equally important. We will help our customers choose proper matching parts and in many cases can supply a complete kit at a competitive price. The tune and pipe are very important as well. Depending where you are located we can suggest high quality tuning shops.

Which porting option is best for my style of riding?
Pumping up torque and widening the curve is the goal. Horsepower comes along for the ride. Fast rev times and midrange torque for passing and roll-on fun are the benefit of this big fat torque curve. The Street Pro TQ package offers an economical, arid very effective way to increase torque. This package is best suited for mild, bolt in cams. The Pro Street package is designed for higher horsepower, wide torque bands, higher compression and higher lift cam shaft applications. We will be happy to discuss your goals and suggest the right package to meet your needs. In some cases a totally custom solution may be desired. We are happy to support.

How much compression do I need?
Compression is set and discussed based on the intended use of the bike, camshaft used, and the cubic inches of the motor. Our head works with a broad range of cams and pipes but some are top performers. I will be happy to help you tailor a combination to your needs.

When are compression releases recommended / required?
If calculated cold cranking compression exceeds 190 pounds, I recommend releases. Using releases even when not absolutely necessary will help the life of the starter system when restarting a hot bike.
We can equip your heads with either ACRs or manual releases. Manual releases are included on all Pro Street and above packages and ACRs are upgrades.

When should I use roller rocker arms?
By properly setting protrusion geometry can be compensated and side thrust minimized. I don’t see any need for roller rockers on builds with .600 or less lift.

What about corrected geometry, what is it and why use it?
We correct geometry on builds that use cams in excess of .625 lift. This is accomplished by using Baisley corrected geometry roller rockers, milling the head top and adding to the length of the valve tips. The result is a very accurate valve train. Mid lift puts the rocker lever perfectly perpendicular to the valve tip and the pushrod lever perpendicular to the pushrod.
Full valve lift realized by no wasted motion
Reduced valve train noise
Longer valve guide life
Pushrods centered in the tube (at mid-lift) prevents potential rubbing
No need for billet offset support plates

What thickness head gasket should I use?
Desired squish is .030 - .035 in most cases. The most common way to get there is by zero decking the pistons and using 030 MLS head gasket. We adjust the head CCs for the proper compression on our head packages.

Do you use my original valves, springs and hardware?
On the Street Pro package we use the stock springs. The stock beehives on the late heads are desirable and control the valves well with most camshafts. If heavier springs are needed they are an option on the Street Pro package and standard on the Pro Street package. New valves are used on all head packages except the “Blueprint”. The valves and seats are highly modified to enhance volumetric efficiency and velocity.

Do you replace the valve guides?
We replace guides with AV&V Bronze Manganese guides on all head packages and it is an option on our Blueprinted heads

Do you have an exchange program?
Not at this time but we may if we transition to CNC work in the future

How long will HD Street Performance have my heads?
This depends on the season. Winter time we get very busy. We have a reservation system that can assure you of the least amount of down time. Please email us for details.

Do you only port Twin Cam heads?
No we port EVO and Sportster heads also. We provide repair services and valve jobs for all models, as time allows.

What other services do you provide? Can you Bore and Hone cylinders?
We can offer many machine shop services including welding on request. We drill manual and automatic compression releases. We can add the front motor mount provision to the twin cam heads that were not drilled.
We do bore and hone cylinders and gap rings for the customers’ convenience.
Our 98 and 107” Bigger Bore kits have proven to be very popular, reliable and cost effective.

Do you offer any type of “Tech Support”?
We help the customer design the engine package. In many cases we can supply the package of complimentary parts. We reserve the right to limit tech support and motor upgrade advise to our current customers due to time constraints.

What kind of warranty do you offer?
We offer a 12 month unlimited mileage no hassle warranty. Top quality products are used throughout that exceeds OEM quality therefore with proper installation and tuning you can expect long trouble free life from your heads.

I’ve seen cheaper porting services, what makes yours worth the money?
The dynos and the customers speak volumes about the work. They are our best sales force. We provide premium parts in an all inclusive package that adds value, quality and performance at an attractive price point.

What are my payment options?

  1. The Intuit Payment Network offers free sales processing by bank transfer. A link is provided with your invoice via email
  2. Check, cash or money orders are also accepted.
  3. We also take Visa and MasterCard via PayPal however there is a customer fee involved

Most of our customers prefer to use personal checks. It's quick and easy. When we receive your check it is deposited immediately so that we can service your order and/or parts as quickly and efficiently as possible.

Where do I ship my heads?
HD Street Performance
1915 111th Ave East
Edgewood, WA 98372

Should I remove any parts from my heads before shipment?
Do not send rockers, rocker boxes or breather parts, unless instructed to do so.

How should I pack my heads for shipping?
Package all heads carefully and use a large volume of bubble wrap or high-density foam. Be sure the head does not move in the box. The most economical way to ship the heads is in one box. Be sure to adequately separate the heads, heads boxed individually and then in a larger box works very well. Be sure there is no contact between heads.
Enclose in the box:
Please download and complete the PDF Order Form and return it with the heads

What method should I use to ship my heads?
USPS, UPS, or FedEx all offer excellent service to our address.