Small block rear main plug?

[tigernut]

According to a webpage I found, there is a oil galley plug that gets installed under the rear main cap:

According to my "How to rebuild a small block chevy" book, this isn't mentioned.

My last engine rebuild was 1988 and I had the block prepped for me before reassembly.

This time, I bought a new block from GM and am having to install all the plugs myself.

Anyone know about this plug? Needed or not?

Thanks,
Doug

 

[JohnZ]

Yes, the plug is required - it's probably not mentioned in the Vizard books because machine shops never remove it - no reason to. If that plug isn't in place, you'll have oil pressure, but no oil will flow through the oil filter, as the pressure will be the same on both sides of the filter.

 

[tigernut]

Thanks John, what you said is what I had previously read so it was good to have confirmation.

Buying a new bare block can be a pain. Went to install my front gallery plugs last night and found that of the three, the two side ones are larger than 1/2", which weren't included in the plug kit (freeze plugs, gallery plugs, etc).

Always something.

Doug

 

[tigernut]

John,

One more question, since this plug is an expansion type plug, it doesn't appear that you can "stake" it in, like the front galley plugs can be. What keeps it from dropping down over time?

DOug

 

[JohnZ]

Dunno - I've never messed with one; always worked with used blocks that already had it in place.

 

[carrollm]

Doug, I just found this out recently also, despite rebuilding a few small blocks. The problem comes when the machine shop pops them out for cleaning, and it goes un noticed during the rebuild. Even the freeze plug set I purchased came without that plug. ( out of sight, out of mind I guess). Anyway, what happens is the oil pressure looks great until the engine gets a little warm, then drops low at idle (red lights/stop signs). Take off and the presure goes back up.

64 mike

 

[tigernut]

Thanks John and Mike.

To follow up, I've read this plug is a 1/2" expansion plug, but on my brand new GM block, it took a 29/64" expansion plug. 1/2" wouldn't even come close to going down the hole.

The 29/64" plug goes loosely down the hole initially, until it gets just past the first set of holes. You then hammer it down where it rests between the first set and second set of holes as John's picture shows above.

Once you hammer it down between the two sets, the walls of the plug squeeze together as they do in the oil galley. I don't see anyway to "stake" it in as you do for the front oil galley plugs. I don't believe it is going anywhere without drilling it out as it seems quite solidly in place.

Doug