Spark Plug Heat Shields?

[Luis_gz06]

Today I was trying to put the stock heat shields in a 72 and only one did not lined up where it bolts. It's on the passenger side where the temperature sending unit goes. Iv'e seen here a few 350's engines with that hole where the shield bolts to. On mine, that mounting hole is not there. It's solid!! Only the one next to the one that's supposed to be there to mount the shield. This is a crate 350 engine that I bought new in my local chevy dealer 6 years ago. Is there something wrong on this crate motor? Why isn't that hole there? Here's a pic. Thanks!

[dukcaln]

Mine has it...........Hmmm

[Wookiee]

I don't think they machine that hole in the newer castings. The boss is there with the extra meat, but they just don't bother. I worked in a machine shop several years ago now and remember having to make the holes for the heat shield for certain applications. Not much help, but you can drill and tap the hole yourself safely.

[Luis_gz06]

Thanks! How would I make the thread if I make that extra hole?

[Legolas894]

Originally Posted by Luis_gz06

Thanks! How would I make the thread if I make that extra hole?

You need a tool called a TAP. Usually you get a tap & die set so you can make threads in holes (drill the hole and use the right size tap) and cut threads on shafts (using a die). I'm not sure about cast iron though. It might be special tools for that. Someone on the forum will chime in.

I've only used my set about 4 times a year but when I've needed it, it's usually on a weekend.