Pointers on Drilling at taping cast iron

[Grim Reaper]

Pointers on Drilling at taping cast iron?

I have managed to get myself in a little jam. I am transplanting a motor. It was originally thought to be a 68 because GM uses a single digit year designation. There is an adapter available from a 68-70 so I thought no big deal. Well it turns out the motor is a 78 and the holes I need for motor mounts are not there. Pads are machined at least.

No adapter for the 78 to a 70 and I think using the newer motor mount is going to sit the motor up too high and my air cleaner will hit the hood...still not sure. With the intake and a 2 inch air cleaner I have less then an inch clearance now and I don't want a high rise hood.

Mild steel, aluminum I have taped but never cast iron. It is going to be a blind hole so I need a blunt nose tap and if I fawk up one of these looks like I'm into the bottom of a cylinder.

Give me some pointers.

[Reflexx]

Cast Iron is "crunchy" not gummy like alum. use a stubby drill with a 135 degree split-point. Make sure you're starting the tap "square" to the hole and use a "bottoming" tap. use a waxy lube or LPS (not wd-40). tap a few threads in and back out, clean, repeat. For every turn of the tap, do a 1/4 turn back to clear the chips.

Should be easy.

[CrustyJeep]

Cast iron drills and taps like butter ;)

Getting the whole drilled and tapped straight will be your biggest challenge...

[Grim Reaper]

Thanks

I wasn't sure if I need to heat (and I was hoping not becasue I just finished paint it) it like you do to weld or anythign weird like that.

Off to Sears I guess. See if they have a decent tap.

[YJBrian]

Just drilled and tapped several motor mount holes on my engine. Cuts nice and easy with cutting fluid.

[krb]

Make sure you're starting the tap "square" to the hole and use a "bottoming" tap.

If it was me, I would start with a plug tap(if the hole is deep enough) then finish with the bottom tap.
If its feasable use a tapping block to keep the tap straight.

[Grim Reaper]

If it was me, I would start with a plug tap(if the hole is deep enough) then finish with the bottom tap.
If its feasable use a tapping block to keep the tap straight.

I didn't get a chance to go get the tap today. going in the morning (have to burn up my roll over vacation days so off this week and hope to get this in the car AND get my 4Runner in and ready for a motor swap) I did plan to buy both taps. I remember trying to start a bottom in the past and it was a pain in the butt.

I'll look at a tapping block as well and see if it will work. Its about a 1inch but 1.25 inch pad and raised on the top and the bolt is 7/16. Might not work.

I'll have to post a picture of this motor once I get it assembled. Its looking sweet.

[Grim Reaper]

If it was me, I would start with a plug tap(if the hole is deep enough) then finish with the bottom tap.
If its feasable use a tapping block to keep the tap straight.

I didn't get a chance to go get the tap today. going in the morning (have to burn up my roll over vacation days so off this week and hope to get this in the car AND get my 4Runner in and ready for a motor swap) I did plan to buy both taps. I remember trying to start a bottom in the past and it was a pain in the butt.

I'll look at a tapping block as well and see if it will work. Its about a 1inch but 1.25 inch pad and raised on the top and the bolt is 7/16. Might not work.

I'll have to post a picture of this motor once I get it assembled. Its looking sweet.