Engine Need to fill dipstick hole. How hard is it to tap cast iron?

evintho · Oct 19, 2021

I need to fill my center mount dipstick hole. I was gonna tap the hole and insert a small plug plug. I've tapped lots of mild steel but how hard is it to tap the cast iron block?

KRUISR · Oct 19, 2021

Why are you getting rid of dipstick?

manicmechanic007 · Oct 19, 2021

Just use silicone
Or use a dipstick tube that had been cut off and a cap welded on it
I would not tap the hole for a plug

evintho · Oct 19, 2021

KRUISR said:
Why are you getting rid of dipstick?

I'm running a front sump pan and the dipstick is in the timing cover.

manicmechanic007 said:
Just use silicone
Or use a dipstick tube that had been cut off and a cap welded on it
I would not tap the hole for a plug

That's a great idea....never thought of that!

General karthief · Oct 20, 2021

I believe you can find a core plug aka:freeze plug, that size, just back it up with a smear of sillycone and ride.

dgollem · Oct 21, 2021

I did a quick internet search and it looks like tapping cast iron is no big deal. Check out google

evintho · Oct 22, 2021

You are correct sir! I did it today. Used a 1/8"x 27 NPT tap, filled it with an 1/8" pipe plug and sealed it with a dab of silicone. Easy peasy!

manicmechanic007 · Oct 22, 2021

Looks good too

manicmechanic007 · Oct 22, 2021

I dare you to tap the freeze plugs
That would be cool

evintho · Oct 23, 2021

Now you got me thinkin'! Haha!

Bird76Mojo · Oct 23, 2021

Threading the "freeze" plugs is not uncommon. A few high end engine builders do it.

If an engine block is gonna crack from freezing, then it's gonna crack. Those plugs aren't really designed to save an engine from cracking. Sometimes they do, sometimes they don't. They're only there as part of the casting process.

Old BOSS 302 blocks had this done from the factory I believe.

Block