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Old 02-01-2011, 05:31 PM   #1
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Default NPT plug size in LT1 heads? Is it 1/4"-20?

Is the NPT plug size in the LT1 heads 1/4"-20? Thanks for any help.
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Old 02-01-2011, 06:01 PM   #2
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i'm thinking it's a 1/4" NPT thread, which has 18 thread pitch.
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Old 02-01-2011, 06:49 PM   #3
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i'm thinking it's a 1/4" NPT thread, which has 18 thread pitch.
Crap! I stripped one of those out. So I just ordered a Helicoil kit. But it was for 1/4"-20. Egh!! I'll get them to cancel it and get the 1/4"-18. Thanks.
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Old 02-01-2011, 07:18 PM   #4
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the thread isn't 1/4-18. NPT is tapered, and probably 7/16" diameter at least.
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Old 02-01-2011, 07:34 PM   #5
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What plug are you talking about?
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Old 02-01-2011, 08:00 PM   #6
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What plug are you talking about?
The one that the steam pipe goes too. I installed the heads the wrong way so I was trying to remove the NPT plug to the other side and in the process of doing that I screwed up the threads.
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Old 02-01-2011, 08:10 PM   #7
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Use a pipe tap and convert to -AN fittings.
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Old 02-01-2011, 08:12 PM   #8
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Egh! I'm an idiot there is no way it is 1/4. There is a guy that listed the parts he used from summit to change his steam pipe over to a braided hose setup. He had the NPT listed as 1/4.
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Old 02-01-2011, 08:16 PM   #9
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Quote:
Originally Posted by RamAir95TA View Post
Use a pipe tap and convert to -AN fittings.
Planned on doing that. I just don't know why that guy had it labeled as 1/4 NPT. I will get the pipe tap for sure.
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Old 02-01-2011, 08:17 PM   #10
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The threads for the steam pipe is actually 1/4 -18 NPSF . It is not a tapered thread but you can tap it with a 1/4 -18 NPT to repair it.
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Old 02-01-2011, 08:22 PM   #11
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The threads for the steam pipe is actually 1/4 -18 NPSF . It is not a tapered thread but you can tap it with a 1/4 -18 NPT to repair it.
Wow I am confused as ever. lol. It looks much larger than 1/4. So 1/4-18 it is.
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Old 02-01-2011, 08:26 PM   #12
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Quote:
Originally Posted by djm_e22 View Post
Wow I am confused as ever. lol. It looks much larger than 1/4. So 1/4-18 it is.
The tap drill for the 1/4 NPT Tap is a 7/16 .It is not a 1/4 dia tap. You'll see when you get the tap. Just make sure to get a 1/4 NPT.
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Old 02-01-2011, 08:28 PM   #13
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1/4" isn't the fitting OD!!!! You need a 1/4 NPT tap for what you're trying to do, it's tapered and you'll start with a 7/16" hole.
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Old 02-01-2011, 08:28 PM   #14
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Z8s treed me
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Old 02-01-2011, 08:35 PM   #15
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I see now. Sorry I got myself confused. Thanks guys.
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Old 02-01-2011, 08:52 PM   #16
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In the world of plumbing pipe, "1/4" inch indicates the inside diameter of a pipe. The outside diameter of that pipe would obviously be bigger. This is why you think it's more than 1/4 inch. You are/were thinking of a 1/4 inch hardware bolt which is much smaller.

Z8's is correct. While it is considered a pipe thread, it's straight, not tapered like a regular pipe fitting. This is why the crossover fittings have seals on them. If it was a tapered pipe thread, they would not need a seal like the coolant temperature sensor in the head.
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Old 02-02-2011, 08:17 AM   #17
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^ Just went through this crap with mine.
Yes, it's a 1/4" NPSF thread. Just like a pipe thread, but straight instead of tapered.
Using a 1/4" NPT tap, you can convert easily to doing -AN fittings.
There are a few write-ups here and there for it. I know Speed Density did one awhile back that I pretty much followed to the T. I think the shopping list is as follows, but you can do it your own way also:
(2) 1/4" NPT to -6 AN (Male-Male)
(2) -6AN to push-lok 90* elbow (Female-Male)
(3) Push-lok to -6 AN straight (Male-Female)
(1) -6 AN "Tee" (All male)
~6-8 feet of -6 push-lok hose

Aeroquip makes the push-lok stuff, and summit has their own brand of it as well. You push the hose right on and forget about it. No clamps needed.
I had to re-do a section of mine (not long enough) and all I had to do was cut it at the fitting with a razor knife, then pull it off with pliers (and used a heat gun to make it a bit easier).
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Old 02-02-2011, 08:29 PM   #18
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Quote:
Originally Posted by qc97z View Post
^ Just went through this crap with mine.
Yes, it's a 1/4" NPSF thread. Just like a pipe thread, but straight instead of tapered.
Using a 1/4" NPT tap, you can convert easily to doing -AN fittings.
There are a few write-ups here and there for it. I know Speed Density did one awhile back that I pretty much followed to the T. I think the shopping list is as follows, but you can do it your own way also:
(2) 1/4" NPT to -6 AN (Male-Male)
(2) -6AN to push-lok 90* elbow (Female-Male)
(3) Push-lok to -6 AN straight (Male-Female)
(1) -6 AN "Tee" (All male)
~6-8 feet of -6 push-lok hose

Aeroquip makes the push-lok stuff, and summit has their own brand of it as well. You push the hose right on and forget about it. No clamps needed.
I had to re-do a section of mine (not long enough) and all I had to do was cut it at the fitting with a razor knife, then pull it off with pliers (and used a heat gun to make it a bit easier).
Yeah I already ordered my AN fittings. The main problem I was having today was finding taps for pipe fittings. Everybody only had them for bolts. I did finally find a set though. Thanks for everybodys help.
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Old 02-02-2011, 09:27 PM   #19
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(NPSF= National Pipe Straight Fuel)

I'm thinking that you should be able to thread into the heads 1/4 inch NPT fittings (National Pipe Thread which is tapered) and get it to tighten and seal without running a 1/4 inch pipe tap through it first. I believe the tapped threads in the head are allready the finished tap size without the taper. Treat it like a pipe fitting and apply some teflon tape.

Before running that pipe tap through the threads, first try the 1/4 inch tapered plumbing fitting.
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Old 02-02-2011, 10:11 PM   #20
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no the 1/4 npt plug will only thread in about half-2/3 of the way. DON'T go crazy tightening it, just use sealant and snug it up.
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Old 02-02-2011, 10:11 PM
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