Cylinder Head tool

There are loads of threads on various forums about machining cylinder heads, and over the years there have been many different methods used.

Those who have done it successfully in significant volumes will know that it is not as simple as a large 3 jaw chuck. Even when a reasonable solution is found there are significant differences in machining datums and casting porosity that make the reprofiling less than a dead cert.

To help everyone on there way I decided to post the assembly and drawing details of a very successful cylinder head jig that I have used for the past 6 years on a CNC lather (it can be used on manual lathes too). The jig holds all versions of cylinder head both big and small block by repositioning the studs. I set a datum on the CNC and run a set path to cut profles and head volumes. Every one has an identical profile and volume (unless I program otherwise), no guess work required.

The jig is designed for manufacture from standard free cutting mild steel (you probably get away with a good grade of aluminium for most of the jig if you wanted). Study the CAD assembly HERE (there is a description of how to use these CAD files HERE) then down load the PDF drawings take them to the shop and away you go.

The cylinder head will get casting patterns made in a few months for both big and small block (you get a blanking plug too). I should also add that the assembly is held together with M8 counter sunk socket heads.

Drawings: Gen assembly, Backplate, Boss, Stud fixing, Stud, Washer.

TS250er piston conversion

This piston is a handy conversion for big block engines with a standard size of 70mm and 2 oversizes it is a suitable and economic candidate for conversion. The onlu problem is with converting the wrist pin to 16mm (standard piston is 18mm).

Previous efforts at sleeving have been a bit hit and miss (usually, but not all the time). So after converting a number of RM250 Wiseco pistons I drew up this "Top Hat" conversion bush that performs the task very well. CNC machined from bronze it is a light press fit and then given a final hone for the perfect fit and alignment (the outer OD is drawn as 18mm but increase this to about 18.05 for the press fit). The assembly allows the use of a standard 16 x 55mm pin. drawing download HERE!

Naturally, this principle can be adapted of any 18mm wrist pin conversion.