Intake Manifold Plug

[Joe C.]

The 3/8" NPT plug in midyear aluminum intakes for cars not equipped with power brakes has a square head. Does anybody have a car with an original plug installed? I'm interested in learning whether or not there are markings on the head, material that plug is made from, and anything else that might be important.
Thanks in advance.

Joe

[Wayne M.]

Re: Intake Manifold Plug

The 1/2" NPT plug in midyear aluminum intakes for cars not equipped with power brakes has a square head. ..... I'm interested in learning whether or not there are markings on the head, material that plug is made from, and anything else that might be important. Joe

Joe -- this is the original plug, either off a '64 '461' manifold around Dec '63 vintage; OR... (I can't remember and may have switched) off a L78 '963' manifold of Feb '65 cast. Bare steel with a touch of rust -- interesting feature is that 'tit' off-center on the head.

[Stuart F.]

Re: Intake Manifold Plug

Looks more like a pimple to me.

Where is this plug? Are we talking cast Iron manifolds only?

Stu Fox

[Wayne M.]

Re: Intake Manifold Plug

...Where is this plug? Are we talking cast Iron manifolds only? Stu Fox

Stu -- pic shows plug from an aluminum manifold, but I see '65 AIM shows square plug (UPC 6, Sheet C1) as part # 445673, (opt 9420756). These would be on the base engine (cast iron manifold). '65 P&A30 Gr 8.971 Pipe plugs; shows the first # as 3/8" Sq. Hd. Dryseal, Plain; the optional is described as 3/8" Sq. Hd. Dryseal, steel [both 3/8"-18].

I also have a cast iron '65 BB manifold #3866948, cast late May, with a headless countersunk hex, but I kinda think this is not original.

All these plugs are located on intake runner for cyl.# 8, forward of the distributor.

[Dick W.]

Re: Intake Manifold Plug

Joe, Wayne, I have taken many of these engines apart over the years and never seen anything, that I thought could be original, with something other than the square plug

[Jeff S.]

Re: Intake Manifold Plug

Joe

The plug size/thread form on intake runner 5-8 should be 3/8-18NPT, not 1/2". The other three female pipe threads (temp sensor, bypass & heater hose nipple) are 1/2-14NPT. Perhaps the boss on your manifold was repaired oversize to accomodate the larger fitting?

[Joe C.]

Re: Intake Manifold Plug

Joe -- this is the original plug, either off a '64 '461' manifold around Dec '63 vintage; OR... (I can't remember and may have switched) off a L78 '963' manifold of Feb '65 cast. Bare steel with a touch of rust -- interesting feature is that 'tit' off-center on the head.

Thanks Wayne............just what I needed.

[Joe C.]

Re: Intake Manifold Plug

Jeff,
Duly noted and corrected above. Yes, the forward 3 coolant taps are 1/2" and the manifold vac tap is 3/8".

[John H.]

Re: Intake Manifold Plug

The plug in my 3872783 iron intake ('67 327/300) is exactly like the one in Wayne's photo above, but the "pimple" isn't as pronounced.

[Rick S.]

Re: Intake Manifold Plug

On my 67 327/350, aluminum intake, it has a circled 7 on the top of the plug.

Rick