header size for small block

[Jerry Clayton]

that engine is already stroked

I always try to use a tube size at least 1/8 larger than the exhaust valve size--many times. this then taking into consideration the tubing thickness, will generally give an ID header size equal to OD valve size-----
Also I use a sparkplug with a piece of tubing welded over it to similate socket and extension for clearance around plugs. try to keep the tube straight for a few inches before turning.The header flange should overlap the port at the top for antireversion purposes