CNC Combustion Chambers

Because of CNC machining commitments we are now unable to undertake any engine work, these pages remain for information purposes only.  But – we will be happy to find someone to help with your job, please phone or e-mail if you need a recommendation.


If you’re building an engine that requires combustion chamber modifications (for a  turbo conversion, or a head that has poor chambers), we can re-machine your chambers for the correct size, shape & compression ratio.  All chambers will then be the same – something that is very difficult to achieve by hand.  On turbo heads this will also save the engine builder from having to machine (& weaken) the pistons, and will be especially useful for YB Cosworth & other turbo heads that have been heavily skimmed.

Some chambers will be created from measurement & drawing (see diagram below), which ensures that all curves & dimensions are correct.  Information can also be gathered by 3D touch-scanning, followed by computer manipulation to correct irregular curves & sizes.  Our computer software will also calculate the volume of the chamber before machining is started.

mid machining finished chamber 3D drawing of CVH hemi CVH hemi mid machining

Although there are other means of lowering the compression ratio of a turbo conversion (decompression plates – here), machining the chamber to the required volume can be regarded as the “correct” engineering solution.  For example – when building a 2.0 litre ZVH, a CVH head with chambers enlarged to 63cc will return a compression ratio of 8.0:1 when fitted to a standard Zetec bottom end without any piston modifications.

3d drawing Ford YBThe minimum amount of material will be removed from the chamber walls, but if a scrap head is available then exploratory machining is carried out to determine casting thickness (we have already done this with both 2WD & 4WD YB Cosworth heads).  During machining the amount of metal removal is equalised around the chamber, valve shrouding can often be reduced, and the area around the spark plug can sometimes be modified (see CVH Hemi drawing & photo above).

Over-skimmed YB Cosworth heads can be re-engineered back to their full volume or bigger, allowing correct deck height and leaving pistons at full strength. Average price for machining all 4 chambers in a YB Cosworth head is £240.00. Pressure testing & resurfacing should be carried out first, and valve seat work should be left until last.

Large capacity ZVH/CVH chambers can be machined for the correct compression ratio (so no piston mods are needed) for just £180.00.

Trade enquiries (especially other engine builders) are most welcome, speak to Mike Tanski for more details.