View Full Version : Suggestions for drilling and tapping a manifold
05-10-2008, 01:05 PM
I don't have a mill, I don't have a 1/2" NPT tap, and I don't have a 23/32" drill bit. But I need a hole in the front of my intake for a heater hose.
I do have a drill press, though. ;)
Would it make sense for me to buy the tap and drill, and do this myself? Since the manifold would have to sit on end and at a slight angle, I'm not sure I could jig this up properly. I'm a little scared to try it freehand too. I don't think it's very critical to get it perfect, but I don't want to screw up the manifold either.
I could take it to a machine shop, but I have no idea what they'd charge me to do this. Also, I don't want to wait a week or two for them to get to it. I'd like to have it done NOW. :rolleyes: :D
What do you guys recommend I do? I don' t know if I'd ever need the tap again, since I have 1/8", 1/4", and 3/8" NPT taps and I don't think I have ever used them.
The hole needs to be just to the left of the bypass hose hole in this picture:
05-10-2008, 01:24 PM
I think you're trying to make this difficult.
I would get out the 1/2" pistol drill and drill it. Then tap it.
It will be very difficult to clamp the manifold to a mill table or drill press table. And difficult to position it under the cutting tool at the angle you need. Not worth the trouble IMO. Hence the pistol drill.
Don't try to drill the hole to the finished size in one step. Start with a small pilot hole and progressively work your way up.
The best jig you can use is to bolt the manifold to the engine so that it won't move as you do your work.
"since I have 1/8", 1/4", and 3/8" NPT taps and I don't think I have ever used them."
Why don't you use them? I use mine quite often. There's always something that needs one.
05-10-2008, 01:28 PM
Laszlo, any idea why GM did not place a hole for this heater hose? did you change something to require the hole to have to be drilled?
I know you have the ability to do this, but this may be one that you may be better off having a machine shop do, from what you have indicated it would take to do. On the other hand if you do this yourself then you have just added to your tool supply:D:cool:
Did some lower intakes have this hole?
05-10-2008, 02:23 PM
Well, I just called a machine shop and took the manifold down to them. They estimated $50-60 for the work, and can have it mid-week.
Rick, you're probably right that I could have done this with a hand drill. But a 23/32" (almost 3/4") drill bit may not be the easiest thing to chuck up in a hand drill, and I don't even have one. I'll bet that drill would cost me $30 alone....if I could even find one. I went and looked for a tap at Home Depot, and they didn't have one. When I was at Grainger I looked up their cost....around $60-80. So I would be looking at almost $100 in tools, that I'll probably never use again. I really don't have the need to drill NPT holes for some reason....usually they're already there, or I weld an NPT bung on.
Marty, if you look at the top of the manifold, you will see two holes there on the passenger side of the water neck.
One is 1/2" NPT and the other 3/8" NPT. I believe the 1/2" hole is supposed to be for a heater hose. However, I need TWO temperature sensors, and I put then in both of those holes. So my only choice is to use the bypass hose hole for the heater, or drill and tap another hole. I've only seen ONE Ramjet maifold in any pics that had that hole, and it was plugged. :rolleyes:
Here's one in a 67 vette:
Here's the same car assembled...note the heater hose...he had the same issue:
05-10-2008, 02:48 PM
I do not want to sound like i am playing off your misfortune, but this sounds like something i should probably go out and get done my self before i get to far on down the line.
What goes on the tapped hole to the right of the center hole of the manifold? seems i never see anything mounted there:confused:
05-10-2008, 03:30 PM
"But a 23/32" (almost 3/4") drill bit may not be the easiest thing to chuck up in a hand drill, and I don't even have one. I'll bet that drill would cost me $30 alone....if I could even find one. I went and looked for a tap at Home Depot, and they didn't have one."
Suggestion, for one time use or limited use cutting tools, buy imports from Enco, MSC, Wholesale Tool, or any of a number of online and local discount industrial supplies. Enco is my favorite, but I use the others too. For drilling holes between 1/2" and 1", I use drill bits with 1/2" shanks - though the set I have is in 1/16" increments, not 1/32". On the other hand, I find that the suggested tap drill size for pipe is sometimes too small for good engagement of the fitting, especially when hand tapping. So using a tap drill 1/32" or 1/16" bigger often helps out.
At one time you were shopping for a mill and a lathe - did you not follow through?
05-10-2008, 03:54 PM
I paid a local machine shop to drill and tap the manifold in my '67 Camaro for a heater hose fitting. They also drilled a hole for the oil fill tube. The total cost for both holes was $100. I think it was worth it.
If you do it yourself donít run the tapered tap in too deep as it will oversize the hole and the fitting will be loose. :eek:
05-10-2008, 04:40 PM
You could use a T fitting in any of those holes to gain 1 more function. I probably would
have used the By-Pass outlet for the heaterhose and put in a By-Pass Thermostat. JMHO
I have also seen T/Stat Hsgs. with threaded holes for sensors.
05-10-2008, 04:57 PM
Couldnt you use the fitting on the manifold (bypass tap) to feed the heater core , the the core return back to the water pump ?
05-10-2008, 05:09 PM
Marty, I don't know what the hole is for to the right of the center hole, but my guess is that it's for an alternator bracket.
Suggestion, for one time use or limited use cutting tools, buy imports from Enco, MSC, Wholesale Tool, or any of a number of online and local discount industrial supplies. [/quote}
I guess I probably should have checked with Harbor Freight, but that didn't even cross my mind this morning for some reason. :rolleyes:
[quote]At one time you were shopping for a mill and a lathe - did you not follow through?
I have found a lathe, but haven't bought it yet. I got distracted with wiring and A/C hoses. Plus I've spent a few thousand dollars on big game applicatons this spring and have to wait to get the money back when I don't draw....as usual. :( I'd like a mill, but I don't know where I'd put it.
If you do it yourself donít run the tapered tap in too deep as it will oversize the hole and the fitting will be loose.
The guy at the machine shop wants me to bring the fitting in for that reason. I thought about it, but left it home. I figured a 1/2" NPT was a 1/2" NPT. :rolleyes:
You could use a T fitting in any of those holes to gain 1 more function.
Well, I'm going for looks as well as function. I think that would have looked cobbled up.
I probably would
have used the By-Pass outlet for the heaterhose and put in a By-Pass Thermostat.
I thought about that, but the angle of the bypass hole wasn't very conducive to using the Aeroqip 90-degree A/C fitting that I have for the heater hose. The other hole gives me a better angle to run the hose behind the idler bracket....it's really tight!
I have also seen T/Stat Hsgs. with threaded holes for sensors.
UGLY. :rolleyes: :eek: :D Plus I have a nice, new, expensive Billet Specialties housing. I need a 0-degree housing and nobody else seems to make one. I think the spacers under the housing look rinky dink too....but that's just my opinion.
Thanks for all the suggestions. I still feel okay about paying $50-60 to have this done. ;)
05-10-2008, 09:48 PM
You made the right decission to have the machine shop do it. To do the job right you would need the drill, a tapered reamer, and the NPT tap. Without the proper tools you run the risk of galling the threads on aluminum.
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