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Intake manifold on this 383 crate iron is #12496820... (Since this engine would go nicely in a Corvette, this question could be considered Corvette related...) In any case, at the front of the intake is a drilled and tapped hole horizontally into the area below the thermostat. I don't know what use I would have for this hole or what it is designed to do. Anyway, it has what I am calling a weird thread. I don't believe it is an NPT thread. Best I could measure would be maybe 5/8 - 20 & that is from a carburetor fitting I finally found that would screw in. But, even then, how does it seal? I'm wanting to reach for the JB weld or the rubber plunger wine "cork", but figured there might be a better answer out there. Thanks, Dennis
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Re: Joe L. et al. Intake H20 Fitting. Stumped Agai
Sounds like a fine thread pipe plug is what you need but I've never heard of one either.
As a last resort you can redrill and tap to the next size bigger NPT size. The cast iron will machine pretty easy.
I wouldn't trust the JB weld approach. That sounds like something you may have lernt from Bubba Mikie back in the Cumberland mountains...
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it is a thermostat bypass hole
and should be connected to the proper type water pump. does this block have a thermostat bypass hole below the water pump inlet,if it does you could block this hole in the manifold but you need a thermostat bypass so water circulates while the thermostat is closedComment
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Re: Joe L. et al. Intake H20 Fitting. Stumped Agai
Dennis----
As clem mentioned, the fitting that you describe is for EXTERNAL bypass provisions. If you use external bypass, then this fitting would be connected to the fitting atop the waterpump in the same manner as was used for all 63-67 small blocks with aluminum intake manifolds. The waterpump supplied with the engine most likely does not even have external bypass provisions, since most 68 and later small blocks used INTERNAL bypass only (through the hole in the passenger side waterpump leg). If you plan to use the waterpump that came with the engine or any other waterpump without external bypass, then you will need to plug this hole in the manifold.
I'm surprised that the fitting is not NPT thread size. Most Gen I and Gen II small blocks and components therefore are made to US thread size. You might want to obtain a 5/8" or 3/4" NPT pipe plug and just try to see if it fits.
If it doesn't, then I expect that the fitting is metric. Based upon your description and measurement, I'd say that the most likely possibility is M18 X 1.5. But, that's just a guess. I'd try the NPT size plugs first.In Appreciation of John HinckleyComment
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Correction
Dennis-----
If the fitting size measures about 5/8" OD, then try a 1/2" NPT pipe plug and NOT a 5/8" or 3/4" NPT. You can get a 1/2" NPT pipe plug in any hardware store. In the event that this turns out to be the right size, you might want to get an indented hex head plug. That will make for the cleanest installation and is always what I recommend for plugging unused NPT fittings.
If the fitting turns out to be metric, you'll still want to use an indented hex or Torx head pipe plug, too. The problem is I don't know where to tell you to get one, so let's hope that it's not metric.In Appreciation of John HinckleyComment
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Thanks for the homework assignment... *NM*
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Re: Thanks for the homework assignment...
just plug it with used bubble gum.Comment
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we call that ABC gum in KS....Allready Been Chewed *NM*
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