Heater Hose Nipple Installation

[Bill B.]

65 327/300

I am in the process of installing 1/2-14 x 5/8 heater hose nipple on my cast iron intake. Intake is not installed on engine at the moment. I ran into a lot of resistance after just a couple of threads. I've tried cleaning the threads as best I can and it's better but still not threading in as far as I'd like. Is there any problem running a 1/2-14 NPT tap in the intake to clean up the threads? I have a new stainless steel nipple to install which I'll use some anti seize on. Thanks in advance.

Bill B.

[Joe L.]

Re: Heater Hose Nipple Installation

65 327/300

I am in the process of installing 1/2-14 x 5/8 heater hose nipple on my cast iron intake. Intake is not installed on engine at the moment. I ran into a lot of resistance after just a couple of threads. I've tried cleaning the threads as best I can and it's better but still not threading in as far as I'd like. Is there any problem running a 1/2-14 NPT tap in the intake to clean up the threads? I have a new stainless steel nipple to install which I'll use some anti seize on. Thanks in advance.

Bill B.

Bill------


There's no problem running a tap into the threads. If it's a thread cutting tap rather than a thread cleaning tap, I would do it carefully, though.

[Bill B.]

Re: Heater Hose Nipple Installation

Thanks Joe. To be honest I've always just used regular taps for cleaning up a hole and don't believe I've used a thread chaser. I'll go slowly. In researching the achieves I see several post (including yours) recommending stainless steel fittings so I've ordered one and hopefully I'll never have to worry about it again. A headache for my heirs, not me.

Bill B.

[Joe L.]

[Terry M.]

Re: Heater Hose Nipple Installation

Bill, I recently removed the heater hose fitting from a 1965 Corvette aluminum intake manifold. It was hard to remove and, unfortunately, pulled some of the aluminum threads out and, worse yet, cracked the manifold. I had the crack repaired by welding and then ran a tap to clean the threads. Another problem...I ran the tap too deep which resulted in a fitment issue for the plug I wanted to install for a dyno test. After doing some research, I found that you could get heli-coils for pipe thread. So, I obtained the needed drill and heli-coil kit and repaired the threaded hole. Worked perfect. I made sure to run a test hole/tap in a piece of 1/2" thick aluminum first to make sure we had the tap depth correct. I had first contacted the manufacturer to get the appropriate tap depth and marked the tap accordingly before tapping. The only downer....the heli-coil kit was expensive. That said, I wanted to save the factory manifold, especially since I had time in it matching the ports to the intake gasket. Hope this helps.

Terry

[Joe L.]

Re: Heater Hose Nipple Installation

Bill, I recently removed the heater hose fitting from a 1965 Corvette aluminum intake manifold. It was hard to remove and, unfortunately, pulled some of the aluminum threads out and, worse yet, cracked the manifold. I had the crack repaired by welding and then ran a tap to clean the threads. Another problem...I ran the tap too deep which resulted in a fitment issue for the plug I wanted to install for a dyno test. After doing some research, I found that you could get heli-coils for pipe thread. So, I obtained the needed drill and heli-coil kit and repaired the threaded hole. Worked perfect. I made sure to run a test hole/tap in a piece of 1/2" thick aluminum first to make sure we had the tap depth correct. I had first contacted the manufacturer to get the appropriate tap depth and marked the tap accordingly before tapping. The only downer....the heli-coil kit was expensive. That said, I wanted to save the factory manifold, especially since I had time in it matching the ports to the intake gasket. Hope this helps.

Terry

Terry------


Cracked manifold while removing heater hose nipple? VERY COMMON. That's exactly why I use and recommend stainless steel nipples. Then, you never have to remove them again.

Running an NPT tap too deep? That's why one has to be very careful when using a thread cutting tap to clean threads.

1/2" NPT Helicoil kit expensive? VERY

[Richard M.]

Re: Heater Hose Nipple Installation

I've found the safest but sadly the slowest method to remove cast iron or steel plugs from aluminum manifolds is to drill them out. Then with extreme caution make several lateral saw cuts on the inside, just enough so as to not touch the aluminum threads. Then remove the pieces with a small pointed drift to drive them inward away from the aluminum threads.

For seized hose fittings, cut the pipe flush to the face and use the same saw cut approach just not too deep into the threads.

It is time consuming. Years ago I saved a FI base plate using this approach and it turned out fine. The Heater hose outlet had a cast iron plug in it that wouldn't budge. The square head broke off trying to free it. I drilled it out in stages, stopped above the threads, and made several wedge cuts. Then tapped them out. Worked fine.

[Mark E.]

Re: Heater Hose Nipple Installation

Why are you guys removing these fittings? Are they corroded to the point they leak? Most of the fittings I've seen look terrible but seal ok and are mostly covered by the hose.

[Terry M.]

Re: Heater Hose Nipple Installation

Hmmmm...good point Mark.

[Bill B.]

Re: Heater Hose Nipple Installation

Mark...I am rebuilding my engine and in the process I found a correct P/N intake (3844459) and the date line up to the date of my vin. Old intake was 3799349. I couldn't budge the nipple at all on the old intake so I gave up and ordered a steel nipple. I found the new nipple would only go in about 3 or 4 threads and go very tight to the point i needed a crescent wrench to go another 2 or 3 threads. I got very worried about cracking the intake so I stopped and got a 1/2-14 tap to clean the threads but now I'm thinking after reading Joe Lucia's warning that I should leave it alone if I can get it in 5 or 6 threads. Looking into the intake I can see 3 threads showing when I had the nipple in as far as I dared tighten. I also ordered a stainless steel nipple that should be here today. I plan on using Teflon tape and maybe anti seize on final installation. Any thoughts?

As always, the experienced members of this board have been invaluable in helping members like me and I appreciate the advice and patience with what are basic questions.

Bill B.

[Joe L.]

Re: Heater Hose Nipple Installation

I've found the safest but sadly the slowest method to remove cast iron or steel plugs from aluminum manifolds is to drill them out. Then with extreme caution make several lateral saw cuts on the inside, just enough so as to not touch the aluminum threads. Then remove the pieces with a small pointed drift to drive them inward away from the aluminum threads.

For seized hose fittings, cut the pipe flush to the face and use the same saw cut approach just not too deep into the threads.

It is time consuming. Years ago I saved a FI base plate using this approach and it turned out fine. The Heater hose outlet had a cast iron plug in it that wouldn't budge. The square head broke off trying to free it. I drilled it out in stages, stopped above the threads, and made several wedge cuts. Then tapped them out. Worked fine.

Rich------


Your method is exactly how I do it when I need to. In fact, I've got a cast iron plug in a Muncie case I need to get on when I get around to it.

[Jeff S.]

Re: Heater Hose Nipple Installation

Bill
You may have more luck with clean up of female threads by using a tap with 'dryseal' threadform instead of 1/2-14 NPT. The crests & root flats of 'dryseal' are more narrow thus insuring sealed/interference fit of when assembled (no sealant req'd). If your recent intake manifold find hasn't been previously chased with NPT taps, it may retain the original GM dryseal female pipe threadform throughout.

[Joe L.]

Re: Heater Hose Nipple Installation

Bill
You may have more luck with clean up of female threads by using a tap with 'dryseal' threadform instead of 1/2-14 NPT. The crests & root flats of 'dryseal' are more narrow thus insuring sealed/interference fit of when assembled (no sealant req'd). If your recent intake manifold find hasn't been previously chased with NPT taps, it may retain the original GM dryseal female pipe threadform throughout.

Jim------


Yes, that's a very important point I should have mentioned.

[Duke W.]

Re: Heater Hose Nipple Installation

You should always use "pipe dope" on NPT fittings, especially with dissimilar materials... both seals and acts and an anti-seize, anti-corrosion coating and is available at any store that sells plumbing supplies.

Duke

[Jeff S.]

Re: Heater Hose Nipple Installation

You should always use "pipe dope" on NPT fittings, especially with dissimilar materials... both seals and acts and an anti-seize, anti-corrosion coating and is available at any store that sells plumbing supplies.

Duke

Good advice, however female heater hose fittings are dryseal 1/2-14 NPSI, not NPT.