Plugs for a de-smogged U20 intake manifold

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Geistfahrar
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Plugs for a de-smogged U20 intake manifold

Post by Geistfahrar »

Back again after the new water pump & tensioner shims are in. I decided to strip all smog parts possible ( including smog water tower ) before installing EI dizzy & GM alt. Extensive forum search failed to identify the plug needed to fill the smog-holes in the intake manifold.

The threaded nipples associated with the air-injection system matched the 18TPI NC tab on my thread gauge, but all the dies in my SAE ( Craftsman ) set are much smaller than the OD of the subject nipple. As the OD is "straight", I don't believe it is pipe thread, so I assume it is metric. Forum comments on the subject included "drilling out the holes & re-tapping." I am reluctant to do that with the manifold on the engine, as I would probably get shavings sucked into the cylinders.

I thought it might be possible to block the bottoms of the holes with epoxy before a drill-out, to prevent chips from entering the manifold, but then, WTH, why not just fill the entire hole(s) with epoxy, & be done with it! Have any of you folks out there done that?

A more elegant ( and reversible ) solution would be to replace the nipples with metric plugs of the correct size. I doubt if these can be found in a plumbing shop, but maybe from a salvage yard or a racing parts dealer.

I am eager to hear any/all who have "been there & done that", before I proceed with "Plan-A" (epoxy).

Garry
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Re: Plugs for a de-smogged U20 intake manifold

Post by notoptoy »

DatsunParts.com has "drop in" replacements with the right thread and nipple end to prevent chirping. https://www.datsunparts.com/2208
Why re-invent the wheel - support the vendors! :-)
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Geistfahrar
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Re: Plugs for a de-smogged U20 intake manifold

Post by Geistfahrar »

Thanks for the reply Tom. I already have Dean's " No Chirp " plugs in the head. I just wanted the top of the intake manifold to look clean as well.

Garry
Location Southern Cal
69' 2000 Roadster, being repaired by O/O
2001 Mercedes ML430; Was Wife's ride, now Grocery-hauler
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2005 33' Dolphin motor-home; Was vacation home, now guest house
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Re: Plugs for a de-smogged U20 intake manifold

Post by notoptoy »

Ahh, so you want to smooth out what is left? Just a cosmetic issue?
It seems like epoxy would work, and you could even add some color to make it look similar. Can epoxy take the heat? I think so, but have no experience in that area.
"When all else fails, force prevails!" Ummm, we're gonna need a bigger hammer here.

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Geistfahrar
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Re: Plugs for a de-smogged U20 intake manifold

Post by Geistfahrar »

When I mentioned epoxy, as a substitute for threaded plugs, I was actually contemplating JB Weld, which can withstand temps of 500 degrees F. A hi-temp version is also available, but I don't really need that. The only down-side is the color ( dark grey when cured ). For the small ( 1/8"NPT ) hole in the center of the manifold I plan to use aluminum filings sprinkled on top of the wet epoxy mix. For the two air-injection holes, I will cut 3/8" discs of 32 GA aluminum, to set in the top of the mix.

BTW, when ordering a new EI Dizzy from EC Roadster, do you prefer the core sent upfront with the order, or returned in the box that the EI unit was shipped in? Since I will not be firing up the engine until the new part is installed, I can go either way. My only ??? is finding a suitable Amazon box to adequately pad-out the shaft. I may have some small ( 4" x 4" ) bubble pillows laying around, but I usually toss them so I don' get crushed by the clutter. It may make a difference if I order the whole enchilada ( EI + coil & wires ), as that would probably come in a larger box.
Speaking of wires, someone on the forum mentioned crossing the wires at right angles, to cancel inductive interference, which would require longer than oem wires for plugs 3 & 4. What is your take on that?

GS
Location Southern Cal
69' 2000 Roadster, being repaired by O/O
2001 Mercedes ML430; Was Wife's ride, now Grocery-hauler
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2005 33' Dolphin motor-home; Was vacation home, now guest house
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Re: Plugs for a de-smogged U20 intake manifold

Post by notoptoy »

GS, probably best to answer your questions off-line via PM, but in short I can handle the core either way - up front or after the fact. I custom make the wires so you can get them any length you want. The dizzie fits nice, and ships cheap in a USPS Priority mail box which is free at your local post office.

Tom
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FergO2k
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Re: Plugs for a de-smogged U20 intake manifold

Post by FergO2k »

I would not recommend epoxy for the intake manifold plugs (the larger ones). I can't remember the diameter of those plugs (mine were in there when I bought my car, have never been removed), but resin that is not fiber supported is going to be brittle, going to incur some degree of shrinkage with the curing cycle, and not deal well with the high vibes going on when mounted to the engine.
Those temp ratings on JB Weld apply to temp excursions, so in service temp is normally 75-100 below that, and they expect you to be using it in thin skin (adhesive bondline) form, not a cast volume.
If anything, chop up some fiberglass or carbon (like 1/8" long whiskers) and make a slurry and this will greatly help both the strength and decrease the exotherm (the heat generated during chemical curing process, which goes up exponentially with volume.
Try a sample of same size off the car before the real one, I would recommend.
So a plumbing plug (Mine has a square drive sticking up) that was then ground to smooth might look presentable.
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keith0alan
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Re: Plugs for a de-smogged U20 intake manifold

Post by keith0alan »

Those are BSPT threads. Threaded plugs from the Z manifold fit.
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Re: Plugs for a de-smogged U20 intake manifold

Post by spl310 »

Keith0alan, do you have that part number? I have seen many manifolds with regular pipe thread plugs crammed into the holes.
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Re: Plugs for a de-smogged U20 intake manifold

Post by keith0alan »

Nissan manifold plugs:

large 08931-3041A
small 00931-30210

It has been some time since I have ordered any through Nissan but they are quite likely still available. They are British Standard Pipe Threads.
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Re: Plugs for a de-smogged U20 intake manifold

Post by Geistfahrar »

Thanks for the part numbers. A quick lookup showed they are still available.

Garry
Location Southern Cal
69' 2000 Roadster, being repaired by O/O
2001 Mercedes ML430; Was Wife's ride, now Grocery-hauler
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Re: Plugs for a de-smogged U20 intake manifold

Post by keith0alan »

No excuse for hardware store plugs in manifolds. They don't fit properly and look awful.
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spl310
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Re: Plugs for a de-smogged U20 intake manifold

Post by spl310 »

keith0alan wrote: Wed Jan 30, 2019 9:16 am No excuse for hardware store plugs in manifolds. They don't fit properly and look awful.
I agree if you are talking about the square head galvanized ones. Brass hex heads look nice.
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Re: Plugs for a de-smogged U20 intake manifold

Post by greydog »

You can buy bspt pipe plugs (square head) from McMaster Carr.
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Re: Plugs for a de-smogged U20 intake manifold

Post by orangedawg »

Does anyone know the actual BSPT thread measurements for the threads in the Solex manifold? I currently have some threaded nipples in there, but the nipple is smooth and doesn't grip the hose I put on there (I use that to hook up to some vacuum gauges to balance the carbs). Also, the straight shaft doesn't grip the caps I put on them when done balancing and they sometimes shoot off the nipple.

Thanks!

Here is what McMaster Carr has:

https://www.mcmaster.com/bstp/hose-and- ... and-water/
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