Head Mods & Rebuild

Turbo Camaro's head and valve train pre-rebuild

Semi-dismantled Chevy 250 head

As mentioned all over the internet, if you had to focus you attention on one part of the Chevy inline 6 to gain power, it would be the cylinder head. The head was cast for stability and economy and requires significant modification and upgrades to get decent performance gains. The following is a list of things you can do to improve the Chevy 250 head for power:

• Install a lump port kit
• Increase valve size to 1.94/1.6 valves
• Complete a full intake and exhaust port job

  

  Hi-Flow lump kit for Chevy inline 6's
  

  
  

Completing the above will require the head to be completely disassembled. Once dissembled you'll want to lap the new valves and prep the head for assembly. It is at this point you may want to mask off the head internals and paint the rest. Replace valve seals and and reassemble the valve train.


When the lump kit was installed in Turbo Camaro, it was filmed and uploaded below.

Valves are waiting to be cleaned and lapped

Valve stems pushed through a pizza box

With the ports opened and the lumps installed, it's time to lap the original valves. Even though extra power can be gained through an increase in valve size, it wasn't in the budget for the initial rebuild. New valves or not, the process of cleaning the head and valves, and lapping them is extremely important. Combustion chamber efficiency and overall compression will be effected by how well the valves are lapped. The process of lapping the valves is simply a way of grinding one surface against another in order to create a flush mating area.

In April 2016, the stock valves used in the Turbo Camaro rebuild were cleaned and lapped. A how-to video was filmed and posted below.

Since Turbo Camaro is received a new performance camshaft, new valve springs were also required. A set of performance springs and retainers were picked up from 12bolt.com. The camshaft has a lift of about .500 while the new springs will handle up to .530.

When you replace or reinstall springs you need to consider some key specs. The amount of pressure the spring will push down when it is compressed and the height at which it is installed. The new springs are designed to be installed at 1.725-1.730". It's a very small window, but with some precision measuring it's very possible to get within this range. The process of measuring and adjusting spring height is very important. A more detailed explanation of measuring spring height, and how it's accomplished was filmed and posted below.

Head ported, lumped and painted. Valve job complete and springs/rockers installed with valve cover.

In the Summer of 2017, the cylinder head was pulled and properly machined. While it was off, it was ported and larger 1.84' intake and 1.6" valves, seats and inserts were installed. A noticeable power increase was obtained from this as the valves allow more airflow and flow in the inline engines is always in demand. The valve guides were also cut to allow for positive valve seals to be used instead of the stock o-rings. The performance springs and original rockers/studs were used for the upgrade.

Freshly installed over-sized valves

Turbo | Camaro