Boring a Head Pipe and Exhaust Manifold

[superstock1986]

Hi Guys and Gals

When boring out a head pipe and mani how far down do you take the 50mm bore? I have the gasket but I am asking how far down you bore it 50mm? Do you take it all the way to where whre the mani splits off? I just don't want anything to get damaged is all.

Thanks

 

[37]

Bore it as far as you can with a boring head, then clean up what you can't bore using a grinder. Transitions need to be as smooth as possible. Any harsh edges create turbulence. You want the runners to open up to the top bore without necking down first.

The headpipe can be tricky to set up in the mill. I've done a few and made a set of standoffs to keep everything square and level on the table. You'll need to be careful on the headpipe since it can only be bored about 3/4" to 1" before you have to grind by hand. Make sure you match the headpipe to the manifold and don't just rely on the existing hole or gasket. Make a template

My best advice is to take your time, measure everything twice, take your time, pay close attention to water jackets, take your time and take your time. Above all, take your time. Oh, and run your boring head slow. It's not a high-RPM process.