plug above the oil filter on 283

[Marvin C.]

I have a oil leak and I'm sure it coming from this plug. Is this plug threaded? Is the only way to stop the leak to drill it out and replace it?

[Bill I.]

Re: plug above the oil filter on 283

Marv, I like you are waiting for the replies, I have never seen this before. The 4 indents are interesting. Like maybe something was supposed to match the indents and bolt in. Bill.

[Joe L.]

Re: plug above the oil filter on 283

I have a oil leak and I'm sure it coming from this plug. Is this plug threaded? Is the only way to stop the leak to drill it out and replace it?

Marvin------


What you have here is a soft plug or as they are sometimes called a drive plug. This same type plug is used on the front of the oil galleries (under the timing cover). In later years this was changed to a much more reliable NPT plug (internal square head). I don't recall just when the change occurred, though.

In order to remove this plug, the best plan is to use a slide hammer with a screw-type attachment. In this case, you would drill a hole in the plug and install the self-tapping type screw attachment. Then, drive the plug out with the slide hammer. You could also drill it out but you'd risk nicking the bore. If that occurred you'd never get a new plug to seal IF you were to use the same type of plug for replacement.

Except if you're concerned with absolute originality, I'd tap the bore for an NPT pipe plug and install that.

The 4 marks surrounding the hole must be some sort of stakings. I don't actually recall seeing these on these older blocks but it's been so long since I did anything on one of these early blocks I'm sure I'd have forgotten by now. I don't understand how stakings this far from the plug could have served to retain it, but who knows?

Addendum: something I should have mentioned, you might have to use a Dremel tool to remove any "influence" of the stakings to retain the existing plug before you pull the plug with a slide hammer. To do this, simply grind a very slight bevel at the opening of the bore so that any protrusion caused by the stakings is eliminated.

[Joe C.]

Re: plug above the oil filter on 283

That plug is threaded. 1/4" NPT. Normally there are 2 plugs in that hole, and they are jam fit together. The photo shows the threaded hole was staked, which indicates that there may NOT be another plug behind the outer one.

The plug goes directly into the main oil gallery exiting the oil filter.

[Joe L.]

Re: plug above the oil filter on 283

That plug is threaded. 1/4" NPT. Normally there are 2 plugs in that hole, and they are jam fit together. The photo shows the threaded hole was staked, which indicates that there may NOT be another plug behind the outer one.

The plug goes directly into the main oil gallery exiting the oil filter.

Joe------

I believe these older small blocks used just a soft plug at this location, like the front oil gallery plugs that were used on small blocks for many years. In any event, this one looks like a soft plug and, if it were a threaded plug, I don't know how they would have installed it----it's not keyed in any way. It's easy to check for a possible threaded plug; just inspect for the presence of threads in the portion of the bore outboard of the lip of the soft plug. I don't think there will be any.

As you say, though, this plug is in the pressurized oil system (just like the front gallery plugs) and if there is ANY leak path, it will definitely leak. In the case of the front oil gallery plugs, one will never know if there's a slight leak. Of course, if one of the plugs falls out (including the plug in question here), one will DEFINITELY know there's a problem (when one's oil pressure drops to zero).

[Dick W.]

Re: plug above the oil filter on 283

It is most definitely a cup or soft plug as Joe Lucia refers to.

[Bill M.]

Re: plug above the oil filter on 283

Marvin------

What you have here is a soft plug or as they are sometimes called a drive plug. This same type plug is used on the front of the oil galleries (under the timing cover). In later years this was changed to a much more reliable NPT plug (internal square head). I don't recall just when the change occurred, though.

The 4 marks surrounding the hole must be some sort of stakings. I don't actually recall seeing these on these older blocks but it's been so long since I did anything on one of these early blocks I'm sure I'd have forgotten by now. I don't understand how stakings this far from the plug could have served to retain it, but who knows?.

My '59 3756519 has soft plugs at the rear and at the front. There are no staking marks at the rear.