I have my old manifolds and spark plugs out. Should I put the headers in first, or the new spark plugs?
Thanks!

 

Never done this before but I was you. Ill put the spark plugs at last..

 

Put the headers in first, you run the risk of breaking a plug or two installing them anyway. And the plugs are much easier to install with headers than the manifolds.

 

Thanks for the quick responses!

 

What he said, I would have left the old plugs in, just to keep anything from falling in the ports. Then once the headers are bolted up swap them all. But definitely wait to put the plugs in till everythings bolted up so you don't run the risk of cracking a new plug.

 

Yup headers then spark plugs