Standard Vs Metric?

[DAS]

I'm changing out the head in my early 67 1600 and the new head has metric threads for the intake and exhaust. What year cars had standard and what year cars had metric? There are two versions in the parts catalog, pre Engine number400001 and later/post number 400001. Which do I use to order studs and other head parts?

[spl310]

The pre 40000 heads are SAE while the post 40000 are Metric. It sounds like your replacement head is a later head. If the head has smog ports, it will be metric. If it does not have the smog ports, but the casting is such that they can be drilled relatively easily, it is Metric (67.5 or non-US market head) and if the head has no provisions for easily installing the smog ports, then it is SAE. All iron heads are SAE.

Also, if the head has smog ports, you can plug them. Some of the vendors may have plug kits (some list them but do not have them in stock) and I believe that Tom Walter makes them occasionally. If you need some fast, take the head to Home Depot and get some allen head screws that will fit down inside the smog ports to plug the lower hole. You want them long enough to fill most or all of that port. Then go over to the plumming aisle and get some pipe plugs (brass is nice) to thread into the smog ports. I used some teflon tape (may not be a good idea in this environment - we will see) on the plugs in hopes that they will not seize to the head (although I never plan to remove them)

As a frame of reference, the custom plugs cost $30+ (although Tom donates a lot of it to a charity, so that is good - kudos for Tom!) while the setup I described cost a whopping $5....

Oh, some folks will tell you to just buy plugs and forget the cap screws. If you do that, you may get a chirping sound from the exhaust. The cap screws are just there to fill the holes and stop the chirp.