In House Machining Services

Flag Motorsports is proud to be able to perform most of our machine work processes in house at our facility in San Marcos, California. We are also proud to have been able to invest in some of the industry leading engine rebuilding and reconditioning equipment. An engine build is only as good as the machine work, making machine work the most crucial aspect of assembling an engine that will be efficient, powerful, and long lasting. Below are some of the machines you can find in our shop, along with some of the features that make them so valuable.

If you need an engine built, or even just machine work done for your engine, consider giving us a call so that your project can benefit from the features and strengths of these machines as well.

Centroid 4 Axis Blockwork CNC Machine

Almost all of our block machine work is done on our Centroid 4 axis CNC machine, including but not limited to:

• sleeving jobs to any LS or LT block

• boring

• decking

• half inch head stud conversions

• stroker clearancing

• DOD tower modifications

We have a specially designed fixture for maximum rigidity to ensure all tolerances are perfectly on spec. This machine allows us to fully sleeve blocks in house, transforming small aluminum 5.3s into big bore Darton sleeved 7.0L blocks. We use this machine for some cylinder head work as well, including but not limited to surfacing, valve jobs, and modifying rocker pedastals on cylinder heads. All of this work is done in-house at our shop in San Marcos, California.

Rottler H85A Cylinder Hone

All of our cylinder honing is performed in house on our 2026 model Rottler H85A. Torque plate hones are our standard, and we utilize an SJ-220 profilometer to measure the surface finish of the bores in microns. The H85A is the top of the line cylinder hone, capable of holding tolerances within .0001 of straightness and roundness across the entire block. This hone uses six diamond stones to ensure correct bore geometry and CBN stones for the perfect finish on the plateau hone. We are able to program the desired cross hatch angle, and the machine will automatically adjust parameters to programmed cross hatch angle and finish the bore to the programmed angle. It also has an automatic roughing and finishing load sensing system so it will short stroke or dwell anywhere it senses a tight area. It is also a machine that uses coolant instead of honing oil, so measurements are immediately accurate and there is no cool-down period.

The universal block fixture bolts through the main caps of a block, meaning that while we only build LS and LT engines here, if you are local to San Marcos, CA and you need any engine block with main caps honed - we can help! If you’d like to see our video demonstrating the capabilities of this hone on an LTR block, click here.

Rottler SG9M Seat and Guide Machine

One of the newest additions to our machining arsenal is our SG9M. This machine is a seat and guide machine, which can perform cylinder head work like seat replacements, guide replacements, and valve jobs. The SG9M spindle is mounted on a sphere which allows the Unipilot to automatically center with the valve guide centerline while the workhead is floating on air cushions. Once air floating stops and the workhead clamps, the Unipilot and valve guide centerline are maintained while cutting the valve seat. The machine has a 15 degree tilt head with a digital angle level sensor, allowing us to cut valve jobs on canted valve heads such as the LT cylinder heads. With its built in vacuum tester, we are also able to ensure the sealing surface of the valve job is correctly cut.

As with the hone, our SG9 is a more universal machine. We have tooling for small block Chevy and big block Chevy heads alongside our LS and LT tooling. If you have a cylinder head that needs work in San Diego county, feel free to contact us to see if we have the tooling to help!