Need help finding correct size plug for intake manifold

[mcshooter]

its probably a 1/8 bpt which if i remember right is only one thread more than a npt . i would try a 1/8 npt plug

[MADMarc]

lol Hans, you make it sound so elegant. As for going npt I really want to avoid messing up the threads even though some people haven't had problems doing the swap considering it is only one thread off. Makes me worry...but hell, maybe I will give it a shot. I'm taking off this weekend but as soon as I find something that will fit I will shoot out my results .

[MaxClass]

How about a simple brass plug. Home Depot, Lowes, Napa, etc.

[MADMarc]

I have to find the correct thread size and depth but will be heading there as soon as I finish with school for the week if I have time to go before I take off for the weekend. Will be swinging by the Depot my first chance.

[Roybatty]

You can also go down to any hardware store pick up a NPT socket head plug. drill it larger and retap. this will give you the plug, a good seal, and will not stick into the plenum at all

May try this on the rear rocker cover; interested in increasing the nipple size that goes to the bubble.

Take the nipple to home depot, find a bolt with similar thread. However, you will find that even the shortest bolt is too long and will stick into the plenum chamber. You'll need to cut the bolt to be shorter but be careful not to mess up the threads too much. seal with nylon crush washer.

I did this with the clutch assist delete. The local Sears has a plethora of hardware. Look for the plastic size gauge that you can hold your bolt right up to, get the size and pitch of threads, it will be a metric one. I used the teflon tape; could look better, but I was lazy about cutting the bolt/plug. Regarding the cluth boost assist delete, make sure you get the check valves correct on tubing or you could lose your brake assist! Hehe

[jba3]

In for the size ... I took mine to home depot back when I did mine, and nothing matched / I'm too stupid. I ended up capping it, I hate looking at it, but I only look under the hood a couple times a year anyway so I've left it down at the bottom of my to do list....

[sketch]

hump de bump. anyone ever figure out the thread size on this spot? or am i going to have to do some experimenting on it?

[sergechronos]

Fairly certain it is 1/8 BPT

[thor'svr4]

I used a 1/8npt on mine and it seamed to fit alright. It may be the bpt thread though since the two are so close it's hard to tell.

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[sketch]

cross posting from the "what did you do today to your 3s" thread to get the answer in here for anyone else who finds this on search

I did that mod a long time ago, and it frees up a fair amount of space (for hands) and simplifies things a lot. Good riddance!

How did you end up plugging the port on the plenum? I had a big vacuum cap on mine for a while, but it didn't hold up well and I just recently blocked that port off permanently. Just curious how you chose to do it

Yeah I think it will end up a lot cleaner this way, though there is still a lot to do on the car, lol.

As for plugging the port... the hole is 1/8 BSPT (also known as 1/8 PT in some metric contexts), and I had a hex plug laying around. Clean the parts well, install with permatex thread sealant.

In the past I have made 1/8 BSPT plugs using a 1/8 NPT brass plug from the hardware store (square drive type used in plumbing), and recutting the threads with the 1/8 BSPT die from my metric tap & die set. With the square drive type of plug you can cut new threads all the way down the plug since there isn't a shoulder on the plug to stop your die.

DSMs and these cars both use 1/8 BSPT all over the place: PCV valve, several fittings on the intake manifold, water temp gauge sensor, oil pressure sensor.... just to name a few. 1/8 NPT will go into these holes about 2 threads and bind (27 threads per inch vs 28, and different taper angle) - and will eventually leak.


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