I'm rebuilding one B21F and one B23F cylinder heads. Everything is going well until I measure vacuum pressure, which is below 15 psi. The valve guides are fine, so I left them alone. Both engines appeared operational and came from junkyards. Everything else on the engines is up to specs. I've used a grinding stone and lapping compound on the valve margins and valve seats. I also plugged up the fuel injector ports on the B21F/CIS system. There's got to be an easier way than lapping, cleaning, assembling, testing, relapping...