Tips on drilling a pyro hole in exhaust manifold

[Ataylor]

I'm going to drill my manifold tonight and was wondering if anyone had any tips for drilling into cast iron.

I'm planning to drill into the top of the driver side manifold between the back two cylinders. From the research that looks like the common spot. It is also as far back as I can get on the manifold since I have automatic tran linkage in the way. Is this the thickest spot to tap?

I'm going to center punch, then drill with a cobalt 1/8", then 1/4", then letter "R", then tap with 1/8" 27 pipe thread tap. I was going to use Rapid Tap fluid for drilling and tapping.

My biggest concern is getting the thickest spot to drill and tap.

Also, from looking around on the internet I read that you don't need to use a lubricant for cast iron. Does that sound right? I figured it can't hurt to use some when drilling, but not sure.

Thanks for any tips anyone can offer,

Archie

 

[redneckaggie]

not much to it, make sure you have a starter tap, I would use fluid, also if you are turbo coat the bit and tap in grease and have the truck running to keep the metal shavings out of the turbo, other than that its not hard to drill through, just have at it.

 

[7.3 powerstrok]

center -punch .oil good R-drill and go no need to start small ...good luck

 

[Russ]

just drill it, R drill no fluid. Cast iron doesn't like fluid.

 

[icanfixall]

Just as posted but one more thing... don't run the drill bit as fast as the drill motor can run it. That will dull the drill bit fast. Cast iron is like sand paper and machined fast it ruins the cutting edge of any tool. About 300 rpm is all you need. Good luck and go easy when tapping the hole. The tap for a pipe thread hole does not go all the way up to the end of the threads. If you do that the threads will be too loose. A pipe threads are tapered threads. Thats how they seal the gas or fluid from leaking past the cut threads...

 

[Ataylor]

Thanks for the tips. I will get it done tonight and hopefully have a working pyro soon. I'm looking forward to firing the truck up as it has been down for over a year. I have done many mods with a Baby Moose being one of them, and want to keep tabs on temps once I get it running. I'm waiting for a Ferret adapter in the mail so I can set the timing once it is running. I'm hoping for next week sometime.

Archie

 

[91dirtydiesel]

When i did mine I used a 1/4 inch ratchet and socket on the tap. Made turning it alot easier compared to the handle more typically used

 

[Knuckledragger]

As someone who makes their living machining cast iron, I can tell you not to bother with lubricant/ cutting oil while drilling. Run the drill motor slightly slow and be careful when center punching the manifold. Cast iron is brittle and thin on manifolds, where you are drilling is not likely to be more than 1/4 inch thick (if that). That's OK because the pipe threads will seal fine. Use oil or grease to tap for a nice finish on the threads.

 

[MIDNIGHT RIDER]

If you are drilling/tapping with the manifold installed, coat the bit AND tap with heavy grease.

The grease will keep most of the drillings/cuttings stuck to the bit/tap instead of dropping into the manifold.

Use a pencil magnet poked through the hole to get out any stray shavings.

If a pencil-magnet won't fit through the hole, magnetize a nail or ice-pick, or whatever and use that.

Like hecanfixall already stated, NPT threads are TAPERED and the biggest mistake most make is to go too far with the tap and then have a loose fitting probe.

Tap a couple threads, try the fit, then tap another thread and try again, and so forth and so on, until the fit is right.

 

[88beast]

and if u dont have a turbo dont worry about shavings no turbo means they will blow right out its much more fun that way and if you have a turbo id consider post turbo for youre location

 

[dakotajeep]

I love how half of these posts contradict each other.

Knuckledragger and icanfixall gave great advise...

No need to worry about shavings as 88beast mentioned unless you turbo it before you drill.

Good luck and hope it went well.

Thad

 

[icanfixall]

Some of us know.... And some of us want to know..... Its that simple. I post from actual life experiances. I try very hard to not be vague in my answers but be positive in what I know. I care enough to pass on what I know will help others. Being "gentle" About posting something differant from others posting is important. Now if someone has been told something like" a new oil pump will blow the rings" or any glow plug is just a good as another I may say that right up off the stable floor right there..... In a courser language... Thats just plain horse crap... I can't count how many times I have been told I'm ruining my heads by porting them with no idea how much to remove because the person telling me this "had a friend that ruined a set of gasser heads doing the same thing I did"... Wow... Nothing could be farther from the truth. The more air you can stuff into a diesel the more fuel you can inject. So the more hp you end up with. A turboed engine has that amount of compressed air waiting on top of the intake valve. When it opens the air is pushed and sucked into the cylinder at whatever boost you are running at. Increase air in... Increase hp out.... A clean port matched port is going going to flow way more than a messed up port that has ruff walls dragging down the volisity of the air flow..

 

[OLDBULL8]

If you are drilling/tapping with the manifold installed, coat the bit AND tap with heavy grease.

The grease will keep most of the drillings/cuttings stuck to the bit/tap instead of dropping into the manifold.

Use a pencil magnet poked through the hole to get out any stray shavings.

If a pencil-magnet won't fit through the hole, magnetize a nail or ice-pick, or whatever and use that.

Like hecanfixall already stated, NPT threads are TAPERED and the biggest mistake most make is to go too far with the tap and then have a loose fitting probe.

Tap a couple threads, try the fit, then tap another thread and try again, and so forth and so on, until the fit is right.

This is exactly how it should be done.

 

[oldblue05]

I pulled my crossover pipe off and put a shop vac on the back of the manifold when I did it, just 4 bolts and it's off... Mine does have a turbo

 

[MIDNIGHT RIDER]

I pulled my crossover pipe off and put a shop vac on the back of the manifold when I did it, just 4 bolts and it's off... Mine does have a turbo

Now, that's an idea I hadn't seen before and should work wonders for shaving removal.