PorKen

There are three plugs in the valley, with a round head, and have an allen key hole to install. (BTW, anyone ever figured out the part number for these?)

The rear one is used 78-86 for mounting the throttle body.
The front and rear ones are used for knock sensors 87-95.

I swear that the ones not used were not threaded, when I cleaned the valleys on my '81, and first 86.5, but maybe I didn't look closely enough.

I want to put in a knock sensor on the front plug on my new 86.5, for a knock light, as a SharkTuning aid.

If it is not threaded, can it be threaded?

Vilhuer

There is two different style plugs. Version which is meant to just cover casting hole and another for mounting knock sensor. Early version is used in center hole up to '95 MY. Early one has inside allen for rotating it, knock version has round threaded hole for sensor mounting bolt and is mounted using outside allen setup. Easiest option to mount sensor is obviously to use correct plug for it. Though PET doesn't seem to list either version.

Mike Simard

Tapping the Alusil block may be a horrible ordeal. Carbide cutting tools cut it nicely but HSS ones protest immediatly.

PorKen

Erkka,

That's right, I forgot. The one which accepts a screw is six-sided for a socket, the plain plugs have an internal allen. The threaded ones are the same for rubber mounts, and knock sensors, aren't they?

...

Mike - I meant tapping the plug.

Vilhuer

Without comparing side by side I would say yes. Anyone have part number for these? Have few around from bad blocks but would really like to get new ones as these are real pain to remove. There isn't enough space around them in block for socket.

Mike Simard

Pork', the sensor ones have a common M8x1.25 tapped hole. If you just need one I have a removed one sitting here you're welcome to, just pm your address.

PorKen

Mike,

Thanks for the offer! I was going to get a couple so I could do the '81, too. I'm ordering some used parts from Intl., today; if I strike out there, I'll hit you up.

PorKen

Int'l doesn't have a part number for it - so it doesn't exist.

They're checking on some bad 16V blocks if they have a couple for me. (BTW, Shane is looking for one too.)

It's probably a $2 part, new, if there was a number for it.

Save those plugs!

PorKen

Int'l didn't have any bad S4 blocks, so I got a pair of threaded plugs from some bad 16V blocks.

Now that I think about it, 78-86 use the threaded plugs for the throttle body rubber mounts, which have a 6mm thread. The S4 knock sensor takes a 8 x 30mm bolt. Doh! I'm going to have to drill and tap the plugs for 8mm.

The knock sensor is 18mm high = 12mm into the plug.

PorKen

Here's a very illustrative pic!


brand new 16V shortblock on eBay

largecar379

good picture of the block valley---

not sure why anyone would order a block with fitted pistons and no crank or rods.....seems kind of strange to me, as I would have ordered a complete short block.

---Russ

Vilhuer

There has to be some part number or at least source for these plugs. Either early rear or S4+ knock sensor plug could be used as substitute for each other with little modification. If nothing shows up I'll have to have some made locally. None of the knock sensor plugs I have are good enough to put them back.

PorKen

Somehow, I got the correct plugs. (Thanks, Tom/parts puller guy.)

They are OD 14x1.5 x ~13, ID 8x1.25 x ~16. The overall size is ~21mm with a 17mm hex.



So far, the closest factory plug I could find which might be a good starting point for drilling out is a 900 124 002 02 - SCREW 14 X 1.5, which is used on early 911's for the crankcase and intake manifold. (It takes a 14 x 18 seal, 900 123 007 70.)

Or a 14 x 1.5 solid brass plug, (like this).

Jim bailey - 928 International

The "somehow" is we pulled them from a dead S-4 block... sometimes it helps to have friends in the parts business I had them looking for one for Shane our frozen buddy from the middle of the Bering Sea but we really do not have a part number nor a bunch of dead blocks to pull them from.

Vilhuer

Peters solid plugs look very promising. Sould be easy enough to add suitable sized threads into them.