Most circle track and bracket racing classes want locked timing, and a stock HEI distributor comes with a vacuum advance canister working against that. This lockout eliminates the vacuum advance so total timing stays where you set it, and it installs without pulling the distributor apart any further than necessary.

MSD 88364 Vacuum Advance Lockout Kit Features:

• Locks out the vacuum advance on most GM HEI distributors.
• Standard equipment on the Circle Track HEI distributor.
• Quick installation, well suited to racing applications.
• Will not work on Pro-Billet HEI distributors.