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[PhilStubbs]

i recently picked up a super mint 1990 silverado 2wd with a 305 that has a rod knock for $300. i have a nice 350 crate engine that is missing one hole in the cylinder head for the a/c compressor bracket. since the truck uses a serpentine belt i dont have a lot of options other than figure out how to mount it all back on. so, has anyone drilled and tapped a cylinder head before? it seems like it would be just like drilling any other steel part, slow drill speed and some lube. there is a water passage behind where i need to put the hole so i figure if i go too far, i can just put some sealant on the bolt threads and be on my way.

any thoughts?

[caged]

its going to be quite hard to keep the hole straight   good luck.

[narfdanarf]

Just did this last week.  My hole was a little oblong, so I tapped it the best I could and put a helicoil in it for strength/round aspect. Worked great.

[bigwig]

its going to be quite hard to keep the hole straight   good luck.

Drill Guide

[PhilStubbs]

I have a drill press that I could do it on. The head isn't on the block yet.

I have just never needed to drill cast iron before, just wondering if it was going to be harder than regular steel to drill

[snm95ls]

I have a drill press that I could do it on. The head isn't on the block yet.

I have just never needed to drill cast iron before, just wondering if it was going to be harder than regular steel to drill

It is actually quite easy from what I recall.  It has been a while, but I think cast iron actually cuts much better than steel.

[PhilStubbs]

That's what I was expecting, but my dad stopped by today and I was talking about it with him and he seemed to think it would be harder. I will find out for sure tomorrow

[caged]

its going to be quite hard to keep the hole straight   good luck.

Drill Guide

Nice I havnt seen one of those before. Cast iron is just as easy to drill as steel from memory, it chips away unlike steel.

[HiProfile]

I have a drill press that I could do it on. The head isn't on the block yet.

I have just never needed to drill cast iron before, just wondering if it was going to be harder than regular steel to drill

One thing we used at the machine shop I worked at was cylindrical slugs with holes drilled in them. Picture a revolver's cylinder, except the ammo holes are various sizes. Harden the hell out of the slug, then you have a compact right angle guide for your drill or taps.

ARP and other mfg's make a special thread sealing compound for headbolts that protrude into the water jacket. Make sure you use that regardless, just in case it's not through but super-thin (and cracks later).

[t_cel_t]

its going to be quite hard to keep the hole straight   good luck.

Drill Guide

damn, fuck a drill press im buying one of those. i didnt even know something like that existed

[Foowee]

I'm sure you've already thought of it, but running a small pilot hole first will probably make things easier on ya... 

[PhilStubbs]

Yea, I'm going to use a drill the size of the bolt to locate the hole through the bracket, but as soon as I have a starting place I will take the bracket off and start with a small drill bit and work my way up.

I have actually had a couple semesters of manual machining under my belt, just never needed to mess with cast iron. How often do you come accross cast iron in the Honda world? Lol

[patsmx5]

don't use any cutting fluid or oil when machining cast iron.

[Foowee]

don't use any cutting fluid or oil when machining cast iron.

What about coolant or water? 

[PhilStubbs]

Not saying I don't belive you, but what are the reasons for that?

[t_cel_t]

i think hes full of shit, but maybe because it will trap the super hard chips?

[HiProfile]

How often do you come accross cast iron in the Honda world? Lol

Stock control arms. Very easy to tell when you burn out the rubber bushings then use a sawzall to cut the steel liner...then cut too far. That was alsmost a disaster.


Since cast iron cuts so easy, in addition to having graphite flakes in it's makeup, you really don't have to use any lube. Just make sure the bit doesn't get hot.

[patsmx5]

Old machinist handbook I used to have said you machine cast iron dry, and use compressed air as a coolant if needed, but never an oil or water based coolant. I don't know why, but that's how I've always done it and it works fine. As HiProfile said, it cuts easy anways.

[rprznt]

Old machinist handbook I used to have said you machine cast iron dry, and use compressed air as a coolant if needed, but never an oil or water based coolant. I don't know why, but that's how I've always done it and it works fine. As HiProfile said, it cuts easy anways.

reason is that cast iron is an extremely basic, poor quality material. has very little tensile strength, not a strong alloy like steel.

its characteristics with machining, drilling and working it are very favourable. the cutting chips are soft and gritty like sand, and it cuts very easily. try and avoid heat to avoid cracking and stress risers etc...

no coolant because there is very little friction there, it feels like it "self lubricates" when cutting, weird shit.