Manifold tapping gone bad - help

[TboneMan]

To make a long story short. I have been working on installing my boost/EGT guages. Drilling and tapping the horn for the boost line went fine.



Not so with the manifold. I think the threads are unusable (effectively trashing the manifold). What you my options? Are there pre-tapped manifolds on the market.



I am a bit gun shy now. I don't know if I want to attempt the manifold tapping again. (too expensive).

 

[Mschevey]

Take a look at this web page.



http://www.smokindiesel.com/ATS.html



Advanced Diesel Technology is just one state south.

Give Andy or Doug a call.



Not only is the manifold pre tapped, it also has slip joint so you don't have to worry about it cracking in the long run.



Mike

 

[BarryG]

You should be able to tap it again with the next bigger size and then use a bushing reducer. If you tapped 1/8npt do it again with 1/4 npt and use a 1/4 to 1/8 bushing. Might be worth a try bushing is only 1. 00 manifold a couple hundred I would guess. You have nothing to lose at this point. Or another option is to use one of those ATS manifolds, however I have no experience with them but others here have used them. Good luck.

 

[Big White Beast]

I agree.....

Re-tap with the next bigger size. Use some cutting oil when tapping. Run the tap in a couple of turns and then back it out to clean the cutters. Then run it in again doing the same thing untill depth is achieved. The reducer will raise the probe height some so I would tap all the way through and shoulder the bushing.



Just my 2¢,



Garrett

 

[DennyDay]

Re-Tap

Even if you have to get some help, try re-tapping before you repace the manifold. Pick up a reducing bushing, steel schedule 80 bushing (won't get this at Home Depot), try a pipe supply house.



When I cut threads in the manifold, I use grease for lube, and make 1 1/2 - 2 turns before I back out and clean trash from tap. Most of the thermocouples are long enough to reach the center of the gas flow with out a problem.



Coat both the bushing and the thermocouple with anti-sieze compound before final assy.



Good Luck

Denny

 

[TboneMan]

Does the 1/4 NPT use the same size whole or do I have to drill it larger?

 

[Ray Torresdal]

1/4 NPT

1/4 NPT calls for 7/16 tap drill. You will want to be careful reaming the hole! We sometimes flatten the cutting edge slightly when drilling brass, or cast iron in situations like this to keep the drill from grabbing. I second the recommendation for using grease on the tap, as it also helps bring chips out, when you back the tap out. Back the tap out often, clean chips off, and replace the grease. You can probably also find a stainless steel bushing for not much more, if you like. You can do this! Ray

 

[Big White Beast]

You drill it slightly larger.

You use a 7/16" drill for 1/4 NPT tap.



Garrett

 

[DennyDay]

Stainless Bushing

I'll second the suggestion of using the stainless steel bushing. If you can't find one maybe one of the guys living near the coast can get one to you.



Try Oke-Go, he is in Texas City, and there is a huge marine hardware place just North of him called Kemah Hardware, they will have it.



Denny

 

[Joe G.]

Take it easy tapping cast iron. The stuff is hard and brittle so it wants to break out in chips instead of shavings. The tap has to be sharp and remove it to clean it every so often so it won't jam. I removed the turbo so I could clean out the chips inside with a magnet and an oily rag. Keep the tap wet with cutting oil.

 

[TboneMan]

Well, I made a couple of phone calls. There is a place in Syracuse that has stainless bushings. In fact he has two grades in the 1/4 to 1/8 configuration.



It looks like I'll give tapping another try. Of course I'll need to by the 1/4" tap also.





Thanks all.

 

[RJOL]

TboneMan,



I'll second the thread about how tough the cast iron manifold is. I couldn't get a tap started by hand when I did mine. I put the tap in a variable speed drill and was able to get it started by putting a lot of pressure on the drill and letting it turn very slowly. Once I got a couple of threads started, I backe the tap out, put it back on the regular hand tap handle, and then began the process of tapping a couple of turns, then backing it out, re-greasing with bearing grease, then tap again. Repeat this process till you get the desired deapth. Clean out the hole with a magnet, and your set to put the reducer in, or the probe if you haven't had to enlarge the hole...

 

[JTroiano]

Did you try using the threads you made? Even if they don't look perfect and it takes a little effort to put in, It won't fall out and should work just fine. Use a little anti-seize to put it in. I'm against stainless bolts or nuts on exaust, even with anti-seize 50% of the time they destroy the threads comming back out.

Jon T

 

[Swamp Donkey]

What did you do to wreck the threads in the first place? A dull tap? Just currious.

 

[Pogodually]

FWIW



I also used heavy duty shop vacuum to clean out any shaving that made it past the grease. This worked for me. Just used a small tube taped to one of the attachments over the new hole in the manifold. So far no problems after 20,000 miles.

 

[Ron Bissett]

Tap Tap Tap

Tap the tap You can use a plug to fill the hole after drilling to proper size for plug the plug can be drilled out on a bench and put in as a plug don't give up . Most cast iron can be arc welded also if small hole to be filled there is on the market a filler to do that too .

 

[kswieringa]

Is it deep enough

TboneMan



Did you tap the hole deep enough?

The tap has to be almost 2/3 of the way through

I couldn't start the threads on the bushing till I had tapped at least

half way up the tap

 

[TboneMan]

Its in! (1/4-1/8 bushing and egt probe)





Thank for all the help.

 

[kswieringa]

Infected

TboneMan





Now the BOMB bug will start to infect you... LOL