Cylinder Head Rebuilding

The cylinder head plays a vital role in how your Triumph engine performs. Our methods and experience, along with modern valve and guide materials, will insure your head makes power and stays trouble free for years to come. 

Whether you are racing, restoring, building a custom, or a desert sled, the cylinder head goes through the same process.

What a valve job consists of...

First is a proper inspection of its condition. The head is dismantled and thoroughly cleaned in an 160ºF Aqueous parts washer. Then comes checking for cracks, damaged threads, warped surfaces, or other irregularities. You will be notified about anything that is out of the ordinary at this time, and discuss solutions to proceed.

After the purpose and requirements of the head are established, the parts are selected and the real work begins. The head is heated in an oven, and new valve guides are installed with the correct interference fit. The head is then allowed to cool for a full day before any machine work is done. The valve guides are then honed to size and measured using specialized Sunnen® equipment. 

After the valve guides are finish honed and cleaned, new seats are ground using a combination of Kwik Way valve seat equipment and carbide valve seat cutters. The valve seat ( 45º ), as well as the throat ( 60º ) and top ( 30º ) angles are established. The valve seat width is also set for intake and exhaust, with the exhaust seat width being the wider of the two for better heat dissipation.

Using coated Kibblewhite Black Diamond valves and C630 bronze guides honed round and straight, Triumph twins can run with as little as .001" intake, and .0015" exhaust valve stem to guide clearance. That is ( .0254mm )  and ( .0381mm ) respectively.  This results in a quieter running head with better heat transfer, and less wear in the future.

These clearances are also used with the Kibblewhite stainless OEM valves and manganese bronze guides too. (Manganese bronze material is very similar to the popular Colsibro guide material in England- more cost effective than C630 but still tough and long lasting)

Finally the installed height of the springs is measured and recorded, and the valve springs are measured on a calibrated spring tester at compressed height. Any balancing between springs can be done with shims at this time. The spring is then compressed to the maximum valve opening based on your camshaft lift to make sure the springs will never stack solid or "coil bind". This is an often overlooked but very important detail that can potentially destroy an engine in some cases.

The head is once again cleaned, then carefully assembled. All parts and specifications are documented on a build sheet along with any special notes or instructions. It is then sealed in a bag and carefully shipped back to you ready to install, or if you are local you can come by the shop to pick it up.

Surface finish and special requirements

If you are restoring an engine, you will definitely want your head to match your engine cases. In scenarios like that we would highly suggest that you clean the head to your specification prior to sending it.

We do not do abrasive blasting in our shop. We do however work with a number of professional surface treatment specialists who are experienced with Triumph and other fragile antique aluminum engine parts. From glass bead to vapor honing, we can help get the surface finish you are looking for while your head is being rebuilt. Please inquire about pricing.

The "secret" valve job

If you want the head to retain its original patina but be clean inside we can do that too. Sometimes this is done so that the head doesn't look "out of place" on an unrestored or original bike. It's kind of like a secret valve job.

Some heads are better than others...

Triumph heads came from the factory with a one angle valve job. The valve seats were cast into the head and in most cases are in different locations in relation to the guide. Each head has its own unique challenges, sometimes caused by a previous mechanic or machinist.

Understanding that not all heads are the same, it is wise to start with a serviceable head. Pitted valve seats can be replaced, Broken fins can be repaired, but sometimes the cost of excessive work exceeds the cost of replacement. If you are going to invest in a professionally built head, make sure you are starting with something worth building.

If you are unsure of your head, please email a photo of the combustion chambers and the top of the head and we will let you know if there are any glaring problems to be aware of.

6mm stem conversion kit

The 6mm kit from Kibblewhite uses specially made valves with .235" (6mm) stems for maximum airflow and weight reduction. The C630 bronze guides are machined for the provided viton seals, and the beehive spring kit has titanium retainers with single groove lightweight keepers. This reduced stem kit is currently only made for the Triumph 650 and 750, with oversize valves optional.

This well designed setup has been proven on the track, the dry lakes, and the street. There is no additional labor charge to install this kit beyond the cylinder head reconditioning cost. Lash caps are available but not necessary. For installation detail or more information please see our 6mm kit page

As of July 2024 our pricing is as follows:
Cylinder head reconditioning                                            $467 plus parts
Spark plug thread repair ( Time-Sert )                              $38 each
Thread repair inserts                                                          $26 each
Remove, cad plate, and reinstall intake manifolds         $104.88 pair
Vapor Honing, Media blasting                                           $TBD
Valve seat replacement                                                      $200 per seat plus materials


Whether it's for a restoration, daily rider, or racing machine, a professionally built cylinder head can make all the difference in the power and efficiency of your engine.

Please contact the shop to arrange shipping, scheduling, or for any questions you may have by clicking here.